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Publication Number: FHWA-HRT-11-070
Date: July 2012

 

Long-Term Plan for Concrete Pavement Research and Technology— The Concrete Pavement Road Map (Second Generation): Volume II, Tracks

TRACK 1. MATERIALS AND MIXES FOR CONCRETE PAVEMENTS

TRACK 1 OVERVIEW

This track will develop a practical, yet innovative, concrete mix design procedure with new equipment, consensus target values, common laboratory procedures, and full integration into both structural design and field QC. As opposed to mix proportioning, mix design engineers a concrete mixture to meet a variety of property or performance targets. The process begins by defining the end product, and then the various materials are selected, proportioned, simulated, and optimized to meet the end-product goals. This track will develop mix design rather than mix proportioning.

This track addresses concrete pavement materials selection, including the use of recycled materials, supplementary cementitious materials (SCMs), and new and innovative materials that will help mixture designers to better achieve performance requirements. Materials selection maintains a certain emphasis on sustainable materials, complimenting research conducted under track 12.

This ambitious track also lays the groundwork for the concrete paving industry to assume more mix design responsibility as State highway agencies move from method specification to a more advanced acceptance tool. To do this, however, the concrete paving industry and the owner-agencies must be able to refer to a single document for state-of-the-art mix design.

The track provides a plan for research in the following areas:

The goal and objectives for this track and the gaps and challenges for its research program are summarized below. A table of estimated costs provides the projected cost range for each problem statement, depending on the research priorities and scope determined in implementation. The problem statements, grouped into subtracks, follow.

Track 1 Goal

Innovative concrete mix material selections and mix design procedures will produce economical, compatible, and optimized concrete mixes integrated into both structural concrete pavement design and construction control.

Track 1 Objectives

The track 1 objectives are as follows:

Track 1 Research Gaps

The track 1 research gaps are as follows:

Track 1 Research Challenges

The track 1 research challenges are as follows:

Research Track 1 Estimated Costs

Table 1 shows the estimated costs for this research track.

Table 1. Research track 1 estimated costs.
Problem Statement Estimated Cost
Subtrack 1-1. Performance-Based Mix Design and Specifications
1-1-1. Performance-Based Cementitious Materials Specifications $1–$2 million
1-1-2. Fresh Portland Cement Concrete Pavement Behavior Models $1–$2 million
1-1-3. Hardened Portland Cement Concrete Pavement Behavior Models $250,000–$500,000
1-1-4. Models to Correlate Ingredient Chemistry and Mix Proportions with Concrete Performance $1–$2 million
1-1-5. Standardized Databases and Electronic Communications Protocols for the Concrete Pavement Industry $250,000–$500,000
1-1-6. Web-Based Training System for Implementation of Portland Cement Concrete Pavement Research Products $500,000–$1 million
Subtrack 1-2. Materials Selection and Testing
1-2-1. Aggregate Tests for Portland Cement Concrete Pavement Mix Characterization $2–$5 million
1-2-2. Characterizing Concrete Materials Variability $250,000–$500,000
1-2-3. Increased Percentages of Reclaimed Asphalt Pavement as an Aggregate for Concrete Paving Mixtures $1–$2 million
1-2-4. Mix Design Considerations with Recycled Concrete Aggregate $1–$2 million
1-2-5. Acceptance Criteria for Using Recycled Aggregate $500,000–$1 million
1-2-6. Waste Materials in Concrete Mixes $1–$2 million
1-2-7. Test Methods to Assess Concrete Ingredients at Delivery $1–$2 million
Subtrack 1-3. Innovative Materials
1-3-1. High-Performance Fiber-Reinforced Concrete Pavements $1–$2 million
1-3-2. Pervious Concrete Pavement Program $500,000–$1 million
1-3-3. Carbon Dioxide-Treated Materials $100,000–$250,000
1-3-4. Reactive Powder Concretes as Ductile Materials $500,000–$1 million
1-3-5. Localized High-Quality Concrete at the Joints $1–$2 million
1-3-6. Alternative Reinforcement Material for Continuously Reinforced Concrete Pavements $500,000–$1 million
1-3-7. Application of Self-Consolidating Concrete for Concrete Paving $500,000–$1 million
1-3-8. Energetically Modified Cement $100,000–$250,000
1-3-9. Advanced Curing Materials $250,000–$500,000
1-3-10. Advancements in Internal Curing of Concrete $250,000–$500,000
1-3-11. Self-Curing Concrete $250,000–$500,000
1-3-12. Cement Containing Titanium Dioxide $100,000–$250,000
1-3-13. Evaluation of Non-Portland Cementitious Materials $1–$2 million
Subtrack 1-4. Materials Proportioning
1-4-1. Portland Cement Concrete Pavement Mix Design System Integration Stage 1: Volumetrics-Based Mix Design (Mix Proportioning) $500,000–$1 million
1-4-2. Portland Cement Concrete Pavement Mix Design System Integration Stage 2: Property-Based Mix Design $1–$2 million
1-4-3. Portland Cement Concrete Pavement Mix Design System Integration Stage 3: Performance-Based Mix Design $1–$2 million
1-4-4. Portland Cement Concrete Pavement Mix Design System Integration Stage 4: Functionally Based Mix Design $1–$2 million
1-4-5. Integrating Recycled Materials into Portland Cement Concrete Mix Design System $500,000–$1 million
1-4-6. Aggregate Models for Optimizing Portland Cement Concrete Mixtures $250,000–$500,000
Subtrack 1-5. Mixture Evaluation
1-5-1. Laboratory Mixer to Replicate Portland Cement Concrete Field Batching $1–$2 million
1-5-2. Laboratory Compactor to Replicate Concrete Paving Practice $1–$2 million
1-5-3. Test Methods to Assess Concrete Performance at Point of Delivery $1–$2 million
1-5-4. Statistical Approaches to Mixture Evaluation and Acceptance $500,000–$1 million
1-5-5. Portland Cement Concrete Mix Durability Tests $2–$5 million
1-5-6. Portland Cement Concrete Mix Compatibility Tests $2–$5 million
1-5-7. Portland Cement Concrete Mix Property Test Development $2–$5 million
1-5-8. Portland Cement Concrete Mix Thermal Tests $500,000–$1 million
1-5-9. Portland Cement Concrete Mix Performance Testing Equipment $2–$5 million
1-5-10. Portland Cement Concrete Mix Functional Testing Equipment $2–$5 million
1-5-11. Expert System for Portland Cement Concrete Mixes $1–$2 million
1-5-12. Support for Federal Highway Administration Mobile Concrete Laboratory Demonstrations $1–$2 million
1-5-13. Portland Cement Concrete Mix Design Equipment for States $1–$2 million
Subtrack 1-6. Post-Construction Pavement Materials Evaluation
1-6-1. Evaluation of Innovative Materials for Use as Dowels, Tie-Bars, and Reinforcing Steel $400,000
1-6-2. Evaluation of Innovative Materials for Use as Jointing Materials $750,000
1-6-3. Evaluation of Innovative Materials for Curing $1 million
Total $38 –$81.3 million

Track 1 Organization: Subtracks and Problem Statements

Track 1 problem statements are grouped into the following six subtracks:

Each subtrack is introduced by a brief summary of the subtrack’s focus and a table listing the titles, estimated costs, products, and benefits of each problem statement in the subtrack. The problem statements then follow.

Subtrack 1-1. Performance-Based Mix Design and Specifications

This subtrack focuses on the development of performance-based mixture designs and specifications from which the other subtracks will feed into. Table 2 provides an overview of this subtrack.

Table 2. Subtrack 1-1 overview.
Problem Statement Estimated Cost Products Benefits
1-1-1. Performance-Based Cementitious Materials Specifications $1–$2 million New AASHTO-formatted specifications for specifying cementitious materials used in concrete paving mixtures. Specifications that will allow the mix designer to make informed choices about the proper materials based on desired level of performance and with a clear understanding of compatibility or performance issues and materials specifications that keep pace with the dramatic changes in the materials themselves.
1-1-2. Fresh Portland Cement Concrete Pavement Behavior Models $1–$2 million Thoroughly documented models, also in computerized form, that can be used to predict the behavior of fresh concrete (e.g., rheology). Models that predict critical fresh concrete properties as a function of the mix to allow the mix design system to consider these factors more objectively.
1-1-3. Hardened Portland Cement Concrete Pavement Behavior Models $250,000–
$500,000
Thoroughly documented models, also in computerized form, that can be used to predict the behavior of hardened concrete. Characterization of hardened concrete properties and behavior to optimize the mix design system for performance.
1-1-4. Models to Correlate Ingredient Chemistry and Mix Proportions with Concrete Performance $1–$2 million Models that help select, proportion, and monitor mixture ingredients on
the fly.
Prediction of the potential performance of a mixture based on the characteristics and proportions of concrete ingredients will help reduce variability and failures in concrete pavement systems.
1-1-5. Standardized Databases and Electronic Communications Protocols for the Concrete Pavement Industry $250,000–
$500,000
Industry standards for nomenclature and for measuring and reporting information and data used by the concrete paving industry. Industry standards that allow data to be assembled in a common format, resulting in a more efficient development effort and a standardized system for the multifaceted concrete pavement industry to use in pooling materials, equipment, and other disciplines.
1-1-6. Web-Based Training System for Implementation of Portland Cement Concrete Pavement Research Products $500,000–
$1 million
A Web-based training system capable of effectively training potential users of the numerous products developed under the performance-based mix design track. Mix design system training from remote locations and a feasible and cost-effective training medium for an age in which broadband Internet access is becoming standard.

Problem Statement 1-1-1. Performance-Based Cementitious Materials Specifications

Cementitious materials as they are currently specified (i.e., by percent replacement) and classified (i.e., by fineness and chemical composition) do not reflect their long-term performance as used in PCC pavements. Current methods of specification and classification also fail to reflect the compatibility of the cementitious materials with aggregates and chemical admixtures. This research will develop a cementitious materials specification that reflects the link between the various properties of the cementitious materials and performance and compatibility issues. The specification should be developed to differentiate the various uses of cementitious materials and their influence on concrete’s fresh properties, such as slump, air void characteristics, and set time, and on concrete’s hardened properties, such as strength and abrasion resistance. Ongoing efforts and specifications being developed through ASTM International and other organizations should be considered.

The tasks are as follows:

  1. Identify existing and ongoing work in developing performance-based specifications for cement, supplementary cementing materials, and cementitious materials, both individually and as a combined material.

  2. Identify a structure for a performance-based specification that includes a suite of tests rationally connected to pavement performance.

  3. Develop an AASHTO-formatted draft specification and evaluate it based on the performance of existing pavement sections as well as the known cementitious materials properties.

  4. Refine the specification based on the evaluation and integrate it into the mix design system.

Benefits: Specifications that will allow the mix designer to make informed choices about the proper materials based on desired level of performance and with a clear understanding of compatibility or performance issues and materials specifications that keep pace with the dramatic changes in the materials themselves.

Products: New AASHTO-formatted specifications for specifying cementitious materials used in concrete paving mixtures.

Implementation: A suite of tests will result that can be used to specify cementitious materials through performance predictions. These tests will provide inputs to the mix design system as well as other research tracks, including process QC.

Problem Statement 1-1-2. Fresh Portland Cement Concrete Pavement Behavior Models

Fresh PCC behavior affects the constructability and performance of PCC pavements, as well as properties that significantly impact the cost and quality of the finished product. Ensuring optimal fresh PCC properties for a paving operation will improve paving efficiency, reduce labor costs, increase paving speed, and result in a finished product that meets durability and functional requirements. Concrete moisture variations, for example, significantly affect most concrete properties, such as strength and shrinkage. For example, distresses such as plastic shrinkage cracking, delamination spalling, and drying shrinkage cracking result from excessive moisture loss during construction. Likewise, the air void system significantly affects pavement constructability and durability. Modeling can predict fresh PCC behavior and pavement performance efficiently based on fresh PCC properties. Modeling also allows virtual adjustments to be made to PCC mixes before trial batching. Multiscale models are needed to predict and guide the entire concrete paving process, from microstructure to performance. More fundamental models will be developed that tie fresh PCC properties to constructability and performance and those properties selected for accurate, reliable, and inexpensive field evaluation. These models will take into account various material properties, climatic conditions, admixtures, and construction techniques available for paving operations. The models will then be incorporated into easy-to-use software for both contractors and owner-agencies that can be incorporated into the broader mix design system developed in this research track.

The tasks are as follows:

  1. Identify existing models suitable for predicting the behavior of a fresh concrete mixture.

  2. Determine the suitability of the existing models to paving mixtures and conduct research to make necessary adjustments.

  3. Develop a beta version of the model through a stand-alone interface and evaluate the predictions against lab and field data.

  4. Develop the final model in a form suitable for rapid incorporation into the mix design system.

Benefits: Models that predict critical fresh concrete properties as a function of the mix to allow the mix design system to consider these factors more objectively.

Products: Computerized models that can be used to predict the behavior of fresh concrete (e.g., rheology) model documentation.

Implementation: This work will result in models that can be used to predict constructability and pavement performance based on fresh PCC properties. The models can be used both during the mix design process and as a replacement or supplement to QC tests during construction.

Problem Statement 1-1-3. Hardened Portland Cement Concrete Pavement Behavior Models

Understanding pavement behavior is essential for the pavement design process, as pavement behavior influences pavement characteristics (e.g., thickness, slab length), joint design, mix design, and construction techniques. Modeling pavement behavior is an efficient way to ensure that the pavement design is adequate for the given conditions. Improved models for understanding hardened PCC pavement behavior are needed to predict critical aspects such as curling and warping, joint functionality, and others. These models should take into account material properties, mix properties, construction conditions, and pavement characteristics. The models should also account for hardened PCC properties, such as creep, coefficient of thermal expansion, zero-stress temperature, slab temperature gradients, pavement support, and environmental conditions, among others. These new models will allow designers, contractors, and owner-agencies to make necessary adjustments to pavement design characteristics during the design process, well in advance of construction, as well as during construction.

The tasks include the following:

  1. Identify existing models suitable for predicting hardened concrete behavior. The models selected should be used in concert with ongoing work in track 2.

  2. Determine the suitability of the existing models for paving mixtures and conduct research to make necessary adjustments.

  3. Develop a beta version of the models through a stand-alone interface and evaluate the predictions against lab and field data.

  4. Develop the final models in a form suitable for rapid incorporation into the mix design system.

Benefits: Characterization of hardened concrete properties and behavior to optimize the mix design system for performance.

Products: Computerized models that can be used to predict the behavior of hardened concrete and model documentation.

Implementation: This work will result in models that predict hardened PCC pavement behavior, presented in the form of easy-to-use software. The models can be employed during the design process and during construction to make design adjustments. This work assumes that the research done in track 2 has been completed. The estimated cost for this research is above and beyond that in track 2.

Problem Statement 1-1-4. Models to Correlate Ingredient Chemistry and Mix Proportions with Concrete Performance

Because SCMs are byproducts, their composition is not subject to process control, except indirectly as required by the primary product. Therefore, they tend to be variable, both within a given facility and to a much greater extent between facilities. Even portland cement will be variable within and between plants, governed by the composition of the raw materials available to them.

Traditionally, concrete has been considered reasonably forgiving because the system contained a limited number of components, tolerances for the final product have been broad, and sufficient time was often allowed for reactions to stabilize. However, Portland cement is extremely complex, comprising multiple phases with interactive reaction kinetics. The material has been studied in detail over many years, and classic texts are available that discuss the reactions of the system. On the other hand, less information is available about the reactions and interactions of SCMs. Most research has focused on the engineering performance of systems containing SCMs rather than on their chemistry.

One of the burning needs is that there is little fundamental understanding of the chemical reactions and interactions of the cementitious system containing SCMs. This has significant implications because it is impossible to predict the effects that variability in the materials will have on the properties of the mixture and the attendant changes in construction practices that are required. In addition, the characteristics of SCMs that are currently measured do not necessarily address the fundamentals that strongly influence concrete performance.

There is a need to correlate ingredient characteristics with mixture performance so that as materials vary, mixture proportions can be adjusted to ensure uniform and reliable performance of the mixture, both in the fresh and the hardened state.

Compounding the issue is the growing use of chemical admixtures that are added to mixtures for a given purpose, such as to increase fluidity, but have profound impacts on hydration rates and mechanical properties. The range of commercially available products is large, continually changing, and, in most cases, surrounded by intellectual property barriers.

This work will require a blend of fundamental inorganic chemistry, concrete technology, and statistical expertise to be completed.

The tasks include the following:

  1. Develop models that correlate analytical data with concrete performance.

  2. Develop and implement training and implementation activities.

Benefits: Prediction of the potential performance of a mixture based on the characteristics and proportions of concrete ingredients will help reduce variability and failures in concrete pavement systems.

Products: Models that help select, proportion, and monitor mixture ingredients on the fly.

Implementation: This work will be implementable immediately.

Problem Statement 1-1-5. Standardized Databases and Electronic Communications Protocols for the Concrete Pavement Industry

Successfully implementing all research products and practices depends on effective communication. Ineffective communication often delays concrete products bound for the market, delays and duplicates paperwork between suppliers and vendors, reduces management efficiency, loses the value added when concrete-related computerized guidelines work together, and decreases data accuracy due to transaction/conversion between incompatible systems or formats, among other problems.

As computing and Internet technologies advance, electronic communication forms become ubiquitous and convenient modes of effective communication. Extensible Markup Language (XML), originally designed to satisfy the demands of large-scale electronic publishing, has become an open standard for exchanging a wide variety of Web data. XML facilitates data generation and reading and ensures that the data structure is unambiguous. The benefits of using a common XML schema in the concrete pavement industries include distributing information (e.g., concrete mixture design specifications, concrete research findings, pavement design/construction information) through the Web or any electronic publishing and syndication service; processing commerce transactions electronically (concrete batch tickets, concrete lab test results); providing transparent management control in a multivendor environment (various contractors, concrete testing labs); formulating queries to obtain desired information (e.g., mix design alternatives, pros and cons of specific practices) from knowledge-based systems; and providing interoperability among various computerized concrete design guidelines/analyses. Both the PCA/NRMCA and American Concrete Institute (ACI) committee 235 have initiated XML schema for the concrete industries. However, a lack of funding and resources has limited progress. NCHRP Project 20-64, XML Schemas for Exchange of Transportation Data (TransXML), resulted in the development of TransXML, a common framework for exchange of transportation data in Extensible Markup Language (XML).(3)

This work will result in a ConcreteXML schema based on the World Wide Web Consortium XML schema design principles and requirements. This ConcreteXML schema, with its own namespace, can then be merged into the TransXML under the overall XML schema framework by the consortium. In developing this working schema, an important task will include standardizing terms and XML vocabularies in all concrete pavement-related industries (e.g., State pavement management, State specifications, cement producers, admixture producers, aggregate suppliers, concrete testing labs, mix design firms, concrete batch plants, material delivery, paving companies, and financial/inventory). Thus, any XML documents based in ConcreteXML can be validated easily and automated for quick and error-proof electronic data exchange.

The tasks include the following:

  1. Identify systems for standardizing databases and electronic communications, such as XML.

  2. Standardize terms and XML vocabularies in all concrete paving-related industries.

  3. Implement a standard ConcreteXML or comparable system for all databases and electronic communications.

Benefits: Industry standards that allow data to be assembled in a common format, resulting in a more efficient development effort; standardized system for the multifaceted concrete pavement industry to use in pooling materials, equipment, and other disciplines.

Products: Industry standards for nomenclature and for measuring and reporting information and data used by the concrete paving industry.

Implementation: This work will result in a standardized protocol for databases and electronic communications for the concrete pavement industries.

Problem Statement 1-1-6. Web-Based Training System for Implementation of Portland Cement Concrete Pavement Research Products

Research project results are often implemented inadequately and thus are used incompletely. A mechanism for adequate research product technology transfer is therefore necessary. A Web-based service that contains information about research products from different research organizations should be developed. This Web-based service should include actual case studies, online software applications, documentation, and other resources to make research findings more accessible to the paving community.

The tasks include the following:

  1. Compile information about new testing equipment and procedures and mix design software, including thorough documentation, case studies, downloadable software applications, photos, and video, if necessary.

  2. Develop Web-based training modules for the software and testing equipment.

  3. Create and maintain a Web site for accessing the training modules, providing updates for new products or refinements to existing products.

Benefits: Mix design system training from remote locations; a feasible and cost-effective training medium for an age in which broadband Internet access is becoming standard.

Products: A Web-based training system capable of effectively training potential users of the numerous products developed under the performance-based mix design track.

Implementation: This research will result in Web-based training modules for new mix design software and testing equipment.

Subtrack 1-2. Materials Selection and Testing

This subtrack identifies issues related to selection and testing of materials for concrete pavement mixes. It includes research related to aggregate testing, material variability, and use of recycled materials in concrete pavements. Table 3 provides an overview of this subtrack.

Table 3. Subtrack 1-2 overview.
Problem Statement Estimated Cost Products Benefits
1-2-1. Aggregate Tests for
Portland Cement Concrete Pavement Mix Characterization
$2–$5 million Various AASHTO-formatted materials specifications and test procedures capable of evaluating aggregate properties most sensitive to the behavior, durability, performance, and function of both paving concrete and the concrete pavement. New and improved aggregate test procedures, providing the mix designer with a more reliable system for selecting and proportioning the optimum aggregate for paving mixtures and ways to avoid potential early durability problems.
1-2-2. Characterizing Concrete Materials Variability $250,000–$500,000 Thorough documentation of each of the sources and degrees of variability in the concrete-making process. Understanding variability well enough to quantify it objectively, thus remaining cost effective in design.
1-2-3. Increased Percentages of Reclaimed Asphalt Pavement as an Aggregate for Concrete Paving Mixtures $1–$2 million Recommendations for using reclaimed asphalt pavement (RAP) as an aggregate for concrete paving mixes. RAP in concrete paving mixes, reducing the amount of RAP that must be disposed, as well as reducing the demand for virgin aggregate for concrete pavements.
1-2-4. Mix Design Considerations with Recycled Concrete Aggregate $1–$2 million Recommendations for using recycled concrete as aggregate in new pavement construction. Recycled concrete for aggregate in new concrete pavements, reducing the amount of reclaimed concrete pavement that must be disposed, as well as the demand for virgin aggregate in concrete pavements.
1-2-5. Acceptance Criteria for Using Recycled Aggregate $500,000–
$1 million
Recommendations for acceptance criteria and test procedures for recycled aggregate and concrete made with recycled aggregate. Established acceptance criteria and test procedures for recycled aggregate in new concrete pavements to promote the use of recycled aggregates, thereby reducing the demand for virgin aggregate for new construction.
1-2-6. Waste Materials in Concrete Mixes $1–$2 million Recommendations (proportions and limits) for the use of waste materials in concrete paving mixes. Use of waste materials in concrete mixes, reducing the amount of waste materials and the demand for cement (which must be produced), while producing a better concrete mix.
1-2-7. Test Methods to Assess Concrete Ingredients at Delivery $1–$2 million Analytical techniques that help monitor mixture ingredients on the fly. Ability to monitor variability of the critical characteristics of ingredients concrete mixtures is critical for effective site QA systems.

Problem Statement 1-2-1. Aggregate Tests for Portland Cement Concrete Pavement Mix Characterization

Aggregates constitute the largest component of nearly all concrete mixes by both weight and volume. As a result, the properties of the concrete mix are driven largely by the properties of the aggregates. Because of the high costs of mining and hauling aggregates, research is needed to develop procedures for identifying the most cost-effective aggregate sources for a construction project that will meet the user’s durability, performance, and functional requirements. The use of an aggregate will take into account the total cost of the material, including consideration of haul distances, material quality, necessary mix design adjustments, and projected long-term PCC performance. An important aspect of this research will be to develop tests that can identify durable aggregates before the quarry wall is mined. Procedures will also be developed (or current procedures revised) for rapidly determining the alkali-silica reaction (ASR) potential of concrete mixes made with this aggregate. Additionally, this research will identify ways to protect existing aggregate sources from urban development and to access sources that are difficult to retrieve due to environmental concerns and/or existing urban development. Above all, the test procedures developed here should clearly link to the proposed mix design system.

While this broad research will require further definition during the framework stage, specific aggregate properties expected to be researched under this task include cleanliness, thermal properties (especially coefficient of thermal expansion), and abrasion resistance, among others. To lower transport costs, lightweight aggregates should also be considered and evaluated.

The tasks include the following:

  1. Identify the needs for aggregate laboratory testing, prioritized based on the impact that the properties have on concrete pavement durability and performance.

  2. Develop AASHTO-formatted aggregate test procedures as needed, establishing clear links to the mix design procedures.

  3. Connect the aggregate test procedures to other tracks, including those for QC and nondestructive testing (NDT).

Benefits: New and improved aggregate test procedures, providing the mix designer with a more reliable system for selecting and proportioning the optimum aggregate for paving mixtures and ways to avoid potential early durability problems.

Products: Various AASHTO-formatted materials specifications and test procedures capable of evaluating aggregate properties most sensitive to the behavior, durability, performance, and function of both paving concrete and the concrete pavement.

Implementation: Many new laboratory tests for concrete aggregates are expected. These tests will feed directly into the mix design system and be the foundation for more advanced tests as the state of the art evolves.

Problem Statement 1-2-2. Characterizing Concrete Materials Variability

This research will document the sources of and solutions to concrete pavement variability. A better understanding of variability in current PCC pavement construction is needed, including stockpiling, batching, transporting, placing, finishing, and curing. Following a synthesis of work done in this area, the researcher should advance strategies to minimize variability through improved equipment, measuring devices, and operator influences. The impact of reducing variability should be assessed for contractor profitability, specification tolerances, and design safety factors. By reducing variability, modern pavement design procedures can be used, resulting in more cost-effective designs that also improve overall pavement performance. The overall influence of variability on design safety and product acceptance must be better understood, especially product acceptance as it relates to the size of the product sample.

The tasks include the following:

  1. Identify information sources for assessing the variability of concrete mixtures and other elements of the concrete paving process. This work should be done in concert with ongoing work in track 2.

  2. Synthesize variability information and collect additional information as needed.

  3. Identify inputs for the mix design system that variability information would affect, considering the most appropriate means to consider risk and reliability in the mix design procedure.

Benefits: Understanding variability well enough to quantify it objectively, thus remaining cost effective in design.

Products: Thorough documentation of each of the sources and degrees of variability in the concrete-making process.

Implementation: This research will result in a better understanding of the sources of variability in the concrete paving process. This information, in turn, can be used in the mix design system to develop more reliable and cost-effective designs. This work assumes that the research done in track 2 has been completed. The estimated cost for this research is above and beyond that in track 2.

Problem Statement 1-2-3. Increased Percentages of Reclaimed Asphalt Pavement as an Aggregate for Concrete Paving Mixtures

One of the main problems with rehabilitating or reconstructing existing asphalt pavement is the question of what to do with the wasted RAP. Much of the time, it is recycled back into a new asphalt pavement or used as embankment material. Though it has been recycled back into concrete on occasion (Austria does it regularly), its use and performance have not been widespread or documented in the United States. This research intends to determine whether RAP can be used as an aggregate in concrete pavements. The specific objectives will help determine the expected performance and potential detrimental effects of using RAP for aggregate in concrete.

The tasks include the following:

  1. Identify previous applications of RAP used as an aggregate in concrete paving mixtures.

  2. Identify the properties of RAP aggregate concrete mixes (e.g., strength, durability, workability) and their suitability for concrete pavement construction.

  3. Conduct laboratory testing and/or field trials of RAP aggregate concrete mixes.

  4. Develop recommendations for using RAP in concrete mixes, with specific guidance regarding acceptable RAP materials.

Benefits: Including RAP in concrete paving mixes, reducing the amount of RAP that must be disposed, and reducing the demand for virgin aggregate for concrete pavements.

Products: Recommendations for using RAP as an aggregate for concrete paving mixes.

Implementation: This project will result in recommendations, including mix design recommendations and limits for RAP properties and for using RAP as an aggregate in concrete paving mixes.

Problem Statement 1-2-4. Mix Design Considerations with Recycled Concrete Aggregate

To determine innovative ways to use recycled concrete in PCC pavements, this research will investigate the boundaries of using recycled materials in bases and two-lift construction by investigating its use in shorter performance life pavements, such as 8-year pavement and investigating the use of portions of the product (i.e., fine or coarse fractions). FHWA’s program for recycled concrete should be reviewed before executing this effort.

The tasks include the following:

  1. Identify previous studies of recycled concrete for concrete aggregate and gaps in the knowledge that still remain.

  2. Identify the properties of concrete made with recycled concrete aggregate (strength, permeability, workability, and durability) and the limits of recycled concrete in new mixes.

  3. Identify applications for concrete made with recycled concrete aggregate, such as two-lift construction and shorter life pavement.

  4. Develop recommendations for using recycled concrete as aggregate in new concrete paving mixes, including mix design and pavement design recommendations and construction procedures.

Benefits: Recycled concrete for aggregate in new concrete pavements, reducing the amount of reclaimed concrete pavement that must be disposed, as well as the demand for virgin aggregate in concrete pavements.

Projects: Recommendations for using recycled concrete as aggregate in new pavement construction.

Implementation: This project will result in recommendations for using recycled concrete as aggregate in new paving mixes, including limits for usage.

Problem Statement 1-2-5. Acceptance Criteria for Using Recycled Aggregate

The use of recycled aggregate in concrete pavement is of great interest for reducing waste and reusing materials available at the job site. Using recycled aggregate will also reduce the amount of aggregate hauled to the job site. Research is needed to determine the applicability of standard tests and acceptance criteria for using recycled concrete as aggregate and PCC comprised of recycled concrete as aggregate.

The tasks include the following:

  1. Identify typical recycled aggregate materials and mix designs for concrete made with recycled aggregate.

  2. Conduct laboratory testing using standard acceptance test procedures on aggregates and concrete mixes made with recycled aggregate.

  3. Evaluate the suitability of these test procedures for recycled aggregates and concrete made with recycled aggregates.

  4. Modify existing test methods or develop new test methods for acceptance testing of recycled aggregate and concrete made with recycled aggregate.

  5. Develop recommendations for acceptance criteria and test procedures for recycled aggregate and concrete made with recycled aggregate.

Benefits: Establish acceptance criteria and test procedures for recycled aggregate in new concrete pavements to promote the use of recycled aggregates, thereby reducing the demand for virgin aggregate for new construction.

Products: Produce recommendations for acceptance criteria and test procedures for recycled aggregate and concrete made with recycled aggregate.

Implementation: This project will result in recommendations for acceptance criteria and acceptance test procedures for recycled aggregate and concrete made with recycled aggregate.

Problem Statement 1-2-6. Waste Materials in Concrete Mixes

Fly ash, silica fume, and blast furnace slag are three common waste products that can be used to replace or supplement cement in concrete mixtures to produce more durable, workable, higher strength concrete. However, other waste materials, such as rice husk ash, palm oil fuel ash, and other agricultural wastes, are also proving to be effective materials for use in concrete. Sludge from paper mills can be heated to form metakaolin, which can be used as an additive for concrete, producing a very impermeable product. In addition, recent studies show the benefits of using rubber particles from used tires to replace fine aggregate in PCC-based concrete used in roads.

The tasks include the following:

  1. Identify alternative waste materials that have been tested in concrete mixes and determine the benefits of these materials.

  2. Establish optimal mix design methods (or material optimization) for the waste materials.

  3. Conduct laboratory testing to identify the properties of concrete mixes containing these materials, including strength, workability, permeability, and durability.

  4. Develop recommendations for using these waste materials in concrete paving mixes, including proportions and limits of their use.

Benefits: Use of waste materials in concrete mixes, reducing the amount of waste materials and the demand for cement (which must be produced), while producing a better concrete mix.

Products: Recommendations (proportions and limits) for the use of waste materials in concrete paving mixes.

Implementation: This project will result in recommendations for the use of waste materials in concrete paving mixes, including proportions and limits.

Problem Statement 1-2-7. Test Methods to Assess Concrete Ingredients at Delivery

Because SCMs are byproducts, their composition is not subject to process control, except indirectly as required by the primary product. Therefore, they tend to be variable, both within a given facility and to a much greater extent between facilities. Even PCC will be variable within and between plants, governed by the composition of the raw materials available to them.

Traditionally, concrete has been considered reasonably forgiving because the system contained a limited number of components, tolerances for the final product have been broad, and sufficient time was often allowed for reactions to stabilize. However, PCC is extremely complex, comprising multiple phases with interactive reaction kinetics. The material has been studied in detail over many years, and classic texts are available that discuss the reactions of the system. On the other hand, less information is available about the reactions and interactions of SCMs. Most research has focused on the engineering performance of systems containing SCMs rather than on their chemistry.

There is a need to develop practical test methods that will be usable and cost effective in characterizing concrete raw materials in a local laboratory. The findings of these methods then need to be correlated with mixture performance so that as materials vary, mixture proportions can be adjusted to ensure uniform and reliable performance of the mixture based on models developed in another project.

Concrete is considered to be a commodity, and, as such, it is extremely sensitive to cost, meaning that QC testing and activities have to be cost effective while minimizing risk of noncompliance with specified requirements.

This work will require a blend of analytical inorganic chemistry and concrete technology expertise to be completed.

The tasks include the following:

  1. Select analytical techniques for concrete ingredients.

  2. Check that the tests selected are appropriate and cost effective.

Benefits: Ability to monitor variability of the critical characteristics of ingredients in concrete mixtures is critical for effective site QA systems.

Products: Analytical techniques that help monitor mixture ingredients on the fly.

Implementation: This work will be implementable immediately.

Subtrack 1-3. Innovative Materials

This subtrack focuses on research on innovative materials for concrete pavement mixtures. This includes materials that will help achieve concrete pavement performance requirements, while also reducing the environmental impact of concrete pavement materials. Table 4 provides an overview of this subtrack.

Table 4. Subtrack 1-3 overview.
Problem Statement Estimated Cost Products Benefits
1-3-1. High-Performance Fiber-Reinforced Concrete Pavements $1–$2 million Design recommendations, construction procedures, and specifications for fiber-reinforced concrete pavement. Fiber reinforcement that will result in high-performance concrete pavement that is less susceptible to microcracking from concrete shrinkage than other pavements, resulting in a more durable, long-lasting pavement.
1-3-2. Pervious Concrete Pavement Program $500,000–
$1 million
Design recommendations, construction procedures, and specifications for pervious concrete pavement for highways. Pervious concrete pavements that will drain water from the pavement surface without the need for a cross slope, improving the safety of the pavement surface, as well as the promotion of the breakdown of chemical pollutants due to the large surface area within the pavement surface.
1-3-3. Carbon Dioxide-Treated Materials $100,000–$250,000 Recommendations for using carbon dioxide-treated materials for concrete pavements. Carbon dioxide-treated materials that will increase strength and the rate of strength development while significantly decreasing permeability, resulting in more durable pavements that can be opened to traffic faster.
1-3-4. Reactive Powder Concretes as Ductile Materials $500,000–
$1 million
Design and material recommendations and construction procedures for using reactive powder concrete (RPC) for ultra high-performance concrete pavements. Ultra high-performance concretes using RPC that are very high-strength concretes with ductility and very low permeability and the possibility of thinner pavement sections and reduced or eliminated reinforcement, resulting in a more durable pavement that is cheaper to construct.
1-3-5. Localized High-Quality Concrete at the Joints $1–$2 million Recommendations for using high-quality materials at the joints in concrete pavements. High-quality material at the joint regions in concrete pavements that may not be affordable for use in the rest of the slab, ensuring better joint toughness and durability and enhancing pavement life.
1-3-6. Alternative Reinforcement Material for Continuously Reinforced Concrete Pavements $500,000–
$1 million
Recommendations for alternative reinforcing materials for continuously reinforced concrete pavement (CRCP). Alternative reinforcing materials that provide better corrosion resistance, bond strength, and modulus of elasticity, as well as lighter materials that reduce labor costs during placement and dependence on a volatile steel market.
1-3-7. Application of Self-Consolidating Concrete for Concrete Paving $500,000–
$1 million
Recommendations for design and construction of pavements using SCC. Better consolidation of concrete around dowels and reinforcement, reducing the need for vibration, resulting in a more durable pavement while reducing labor costs during construction.
1-3-8. Energetically Modified Cement $100,000–$250,000 Recommendations for the use of energetically modified cement (EMC)
for concrete paving mixes.
EMC with faster strength development and better long-term strength of blended mixes, resulting in more durable pavements using blended mixes that can be opened to traffic sooner.
1-3-9. Advanced Curing Materials $250,000–$500,000 Recommendations for advanced curing materials and the requirements for these materials. More effective curing materials for concrete paving operations, especially those constructed under short construction windows and in extreme environments and advanced curing materials that better ensure the necessary curing requirements, resulting in a more durable pavement.
1-3-10. Advancements in Internal Curing of Concrete $250,000–$500,000 Mix design recommendations that will promote internal curing (IC) of concrete pavements. IC that will help reduce autogenous shrinkage and self-desiccation and will ensure more complete hydration of cementitious materials, resulting in a less permeable, stronger, more durable pavement.
1-3-11. Self-Curing Concrete $250,000–$500,000 Recommendations on materials and techniques for constructing self-curing concrete pavements. Self-curing concrete pavements that will reduce dependence on the contractor to apply adequate curing measures to new concrete pavement and more complete hydration of the cementitious materials, resulting in stronger, less permeable, and more durable concrete pavements.
1-3-12. Cement Containing Titanium Dioxide $100,000–$250,000 Recommendations for the use of cement containing titanium dioxide in concrete paving mixes. Concrete pavements containing titanium dioxide that potentially can remove certain volatile organic compounds (VOCs) from the air, helping to reduce air pollution in urban areas.
1-3-13. Evaluation of Non-Portland Cementitious Materials $1–$2 million Performance-based protocols and specifications for cementitious materials. Ability to rapidly evaluate and accept innovative materials as they become available, thus improving sustainability of concrete pavements.

Problem Statement 1-3-1. High-Performance Fiber-Reinforced Concrete Pavements

In recent years, advancements have been made regarding the use of fiber reinforcement for improving concrete pavement performance. The first goal of this project will be to synthesize the information available about this topic. Researchers could then determine the potential of advanced fiber concepts aimed at extending the long-life pavement category. Attention should be given to both the benefits and drawbacks of using fiber reinforcement. The end product would include both procedural and analytical guidance for the optimum use of fibers. It is anticipated that this research will explore the field of fracture mechanics and will improve the understanding of the impacts that fibers can play on load transfer (as compared to dowels and tie-bars).

The tasks include the following:

  1. Identify different fiber types and previous use of fibers in concrete pavement.

  2. Identify desirable properties for paving concrete with fibers to achieve long life high-performance pavements.

  3. Identify, through lab testing or field tests, optimum fiber types and proportions for different paving applications (including varying climates).

  4. Develop design recommendations, specifications, and construction procedures for incorporating fibers into paving concrete mixes.

  5. Evaluate design recommendations and construction procedures in pilot projects.

Benefits: Fiber reinforcement that will result in high-performance concrete pavement that is less susceptible to microcracking from concrete shrinkage than other pavements, resulting in a more durable, long-lasting pavement.

Products: Design recommendations, construction procedures, and specifications for fiber-reinforced concrete pavement.

Implementation: This project will result in design recommendations, construction procedures, and specifications for fiber-reinforced high-performance concrete pavement.

Problem Statement 1-3-2. Pervious Concrete Pavement Program

Pervious or porous concrete pavement has several notable advantages over conventional concrete pavement, primarily noise reduction and better drainage. Certain types of pervious pavement can pass 3–5 gal of water per minute, which is much greater than most conceivable rain events and very effective in reducing hydroplaning risk. Porous concrete also offers improved filtration and an enormous amount of surface area to catch oils and chemical pollutants, which can reduce skid and environmental damage. Some experts believe that the bacteria living in these spaces breakdown pollutants, preventing much of the runoff pollution that normally occurs with traditional pavements. However, most of the pervious pavements constructed thus far have been for parking lots, not highways. This research would investigate the use of pervious concrete in highway pavements, examining the advantages and disadvantages, including the feasibility of large-scale pavement construction. The study should examine long-term maintenance and durability issues, such as permeability, abrasion resistance, and wetting/drying, as well as the effect of the bacteria. Stages of this research would include the development of mix design techniques as well as the field trial phase.

The tasks include the following:

  1. Identify previous applications of pervious concrete use for pavements (including bases and subbases).

  2. Identify required properties for application of pervious concrete to highway pavements.

  3. Identify construction requirements for pervious concrete pavements, including pavement structure (e.g., subgrade and base).

  4. Develop design recommendations, specifications, and construction procedures for pervious concrete for highway pavements.

  5. Develop pilot projects for testing pervious concrete pavement for highway applications.

Benefits: Pervious concrete pavements that will drain water from the pavement surface without the need for a cross slope, improving the safety of the pavement surface; promotion of the breakdown of chemical pollutants due to the large surface area within the pavement surface.

Products: Design recommendations, construction procedures, and specifications for pervious concrete pavement for highway pavements.

Implementation: This project will result in design recommendations, construction procedures, and specifications for using pervious concrete for highway pavements.

Problem Statement 1-3-3. Carbon Dioxide-Treated Materials

The treatment of cementitious materials with gaseous carbon dioxide to achieve rapid strength development has been studied for many years. Recently, advances have been made in the treatment of cementitious materials that will facilitate the use of supercritical carbon dioxide in achieving a tenfold reduction in permeability, while strength increases by several fold. While the precast concrete industry already uses this technology, further research is needed to apply the technology to pavements. In particular, research is needed to better understand the mechanisms of rapid strength development in concrete with SCMs. With further research, this process could likely lead to the development of new materials from novel waste streams and accelerate the development of new and improved concrete mixtures.

The tasks include the following:

  1. Identify previous applications of carbon dioxide treatment to concrete materials.

  2. Identify beneficial properties for pavements using carbon dioxide-treated materials.

  3. Identify procedures for incorporating carbon dioxide into materials for concrete pavements.

  4. Conduct laboratory testing and/or pilot projects to evaluate carbon dioxide-treated materials for concrete pavements.
  5. Develop recommendations for using carbon dioxide-treated materials for concrete pavements.

Benefits: Carbon dioxide-treated materials that will increase strength and the rate of strength development, while significantly decreasing permeability, resulting in more durable pavements that can be opened to traffic faster.

Products: Recommendations for using carbon dioxide-treated materials for concrete pavements.

Implementation: This project will result in recommendations for using carbon dioxide-treated materials for concrete pavements.

Problem Statement 1-3-4. Reactive Powder Concretes as Ductile Materials

With a technological breakthrough at the beginning of the 1990s, RPC offered compression strengths in excess of 29,000 psi, flexural strengths of over 5,800 psi, and ductility. Ductal® and BSI®, two products of the RPC family developed in France, are considered ultra high-performance concretes. They are ductile materials capable of resisting substantial flexural loads and do not require passive reinforcement. This allows the overall thickness of structural elements to be reduced. The material is also extremely durable with very low permeability. Thus far, this material has been used predominantly in Europe for concrete structures, but future research should investigate its use in concrete pavements with or without fibers.

The tasks include the following:

  1. Identify RPC mixtures that could be used for concrete pavement, the properties of these mixes, and the advantages of these mixes (e.g., elimination of reinforcement).

  2. Identify the properties required to use RPC in concrete pavement.

  3. Conduct laboratory testing and/or field trials using RPC for concrete pavement construction.

  4. Develop pavement design recommendations, specifications, and construction procedures for concrete pavements constructed using RPC.

Benefits: Ultra high-performance concretes using RPC that are very high-strength concretes with ductility and very low permeability and the possibility of thinner pavement sections and a reduction or elimination of reinforcement, resulting in a more durable pavement that is cheaper to construct.

Products: Design and material recommendations and construction procedures for using RPC for ultrahigh-performance concrete pavements.

Implementation: This project will result in design and material recommendations, specifications, and construction procedures for using RPC to achieve ultra high-performance concrete pavements.

Problem Statement 1-3-5. Localized High-Quality Concrete at the Joints

Many concrete pavement failures occur because of joint damage. Improving the quality of the concrete at these potential weak areas would increase the overall pavement life. Therefore, a system should be developed to ensure that the concrete at the joints consists of a higher quality material than the concrete midslab. This process could involve introducing fibers, chemicals, or other additives at the joints.

The tasks include the following:

  1. Identify joint failure mechanisms in concrete pavements.

  2. Identify possible materials (i.e., high-quality concrete) for improving the toughness and durability of joints.

  3. Develop construction techniques for incorporating high-quality material into the paving process at the joints.

  4. Conduct field trials/accelerated pavement testing of pavements constructed with high-quality materials at the joints.

  5. Develop design recommendations and construction procedures for concrete pavements with high-quality materials at the joints.

Benefits: High-quality material at the joint regions in concrete pavements that may not be affordable for use in the rest of the slab, ensuring better joint toughness and durability and enhancing pavement life.

Products: Recommendations for using high-quality materials at the joints in concrete pavements.

Implementation: This project will result in design construction recommendations for using high-quality materials at the joints in concrete pavements.

Problem Statement 1-3-6. Alternative Reinforcement Material for Continuously Reinforced Concrete Pavements

Steel reinforcement is a critical component of CRCP. However, factors such as concrete permeability and water infiltration at cracks, the resulting corrosion of steel reinforcement, and the associated tendency of concrete to lose bond action with imbedded reinforcement reduce structural performance over time. Research is needed to develop economical, thermodynamically durable, metallic, and nonmetallic corrosion-resistant reinforcements. Widespread use of these technologies, which have been researched for many years, will lead to additional refinements, such as the further development of fiber-reinforced plastic (FRP) bars with a useful form of pseudo-ductility that makes full use of their strength. Another advantage of alternate reinforcing materials for CRCP is reduced placement costs. Lightweight FRP bars require less labor to be installed. Researchers should begin by examining work that has been done previously in this area, including ongoing studies sponsored by FHWA.

The tasks include the following:

  1. Identify alternative metallic and nonmetallic reinforcing materials.

  2. Evaluate the suitability of these materials for CRCP construction, considering properties such as strength, modulus of elasticity, bond strength, corrosion resistance, ductility, cost, and constructability.

  3. Conduct laboratory testing and/or pilot projects to evaluate the viability of these materials for CRCP construction.

  4. Develop recommendations for types and usage of alternative reinforcement, including design recommendations based on properties of each specific material.

Benefits: Benefits include alternative reinforcing materials that provide better corrosion resistance, bond strength, and modulus of elasticity, as well as lighter materials that reduce labor costs during placement and dependence upon a volatile steel market.

Products: Products include recommendations for alternative reinforcing materials for CRCP.

Implementation: This project will result in recommendations for the design and use of alternative reinforcing materials for CRCP.

Problem Statement 1-3-7. Application of Self-Consolidating Concrete for Concrete Paving

Significant interest in recent years has risen over the use of self-consolidating concrete (SCC) for various applications. The most common application is in complex structural work, where the presence of the reinforcing steel has made adequate consolidation using conventional means difficult. Because some concrete paving work faces similar challenges with consolidation (near dowels and reinforcements), using SCC for concrete paving has been suggested. As part of this effort, researchers will evaluate innovative ways to incorporate SCC into PCC pavements that include full sections, overlays, inlays, and patching for both fixed- and slipform operations. This research will build on work already underway by FHWA and other organizations.

The tasks include the following:

  1. Identify previous applications of SCC for pavements or slab on grade.

  2. Identify desirable mix properties for using SCC in pavements.

  3. Develop mix design recommendations for using SCC for pavements.

  4. Develop best practice construction procedures for using SCC for new construction, overlays, inlays, and patching.

  5. Conduct lab testing and/or pilot projects to test SCC for pavements, including an evaluation of consolidation around dowels and reinforcements.

Benefits: Better consolidation of concrete around dowels and reinforcement, reducing the need for vibration, resulting in a more durable pavement while reducing labor costs during construction.

Products: Recommendations for design and construction of pavements using SCC.

Implementation: This project will result in design recommendations and best practice construction procedures for using SCC for pavements.

Problem Statement 1-3-8. Energetically Modified Cement

One important constraint of using cement blended with various pozzolanic or cementitious substances (e.g., fly ash and blast furnace slag) is the early strength development requirements included in current standards. Blended cements typically take longer to develop their strength and often do not meet standards without additives. EMC is a patented technology that has overcome this obstacle. By intensively grinding and activating the cement together with the pozzolan, the surfaces of the particles are activated. Investigators believe that the activation creates a network in the cement particles of submicrocracks, microdefects, and dislocations that allows the water to penetrate deeper into the cement particles, which in turn uses a higher percentage of the potential binding capacity of the cement. This process also activates inert fillers, such as fine quartz sand. The EMC technology is based solely on grinding; no additives of any kind are used. Evaluations and tests of concretes and mortars made with EMC have shown EMC to perform significantly better than portland pozzolan-blended cements containing 20–40 percent fly ash. EMC with fly ash, by comparison, allows a 10 percent reduction in water-cement ratio, translating to higher long-term strength. EMC also showed slightly improved sulfate resistance, and the workability of EMC was better than cement.

The tasks include the following:

  1. Identify the EMCs and cement-pozzolan blends and their specific properties (e.g., strength, permeability, workability, and long-term performance).

  2. Identify the benefits of using EMC for concrete pavement mixes and evaluate the suitability of its properties for concrete pavement construction, considering cost and the variable climates in which the pavements are constructed.

  3. Develop recommendations for using EMC for concrete paving mixes, considering proprietary specifications.

Benefits: Benefits include EMC with faster strength development and better long-term strength of blended mixes, resulting in more durable pavements using blended mixes that can be opened to traffic sooner.

Products: Products include recommendations for the use of EMC for concrete paving mixes.

Implementation: This project will result in recommendations for the use of EMC for concrete paving mixes.

Problem Statement 1-3-9. Advanced Curing Materials

Curing methods used for concrete paving have not changed significantly in the past 30 years. Liquid curing compound remains the most commonly used form of protection. However, the demands being placed on concrete paving are evolving. Rapid reconstruction and extreme weather events have challenged traditional curing methods and demand better solutions. This project will investigate new and advanced curing materials for these extreme circumstances. Effectiveness, cost, and proprietary issues should be considered. Ideally, the project will result in a performance or end-result standard for advanced curing materials that would allow adequate competition and provide the user with the desired properties. To further this goal, a functional specification could be developed that establishes critical moisture and temperature conditions required to achieve varying degrees of quality. The ability of the cure to meet these functional thresholds would determine its quality.

The tasks include the following:

  1. Identify advanced curing materials that could be used for concrete pavement construction, soliciting ideas for new materials if the number of existing materials is limited.

  2. Evaluate the effectiveness of these materials with consideration given to special circumstances such as rapid reconstruction and extreme climatic conditions.

  3. Develop recommendations for required effectiveness of curing materials, considering critical moisture and temperature conditions under which the materials must provide adequate curing conditions.

  4. Develop recommendations for advanced curing materials, ensuring that the requirements are such that a sole proprietary product is not the only available material.

Benefits: More effective curing materials for concrete paving operations, especially those constructed under short construction windows and in extreme environments and advanced curing materials that better ensure the necessary curing requirements, resulting in a more durable pavement.

Products: Recommendations for advanced curing materials and the requirements for these materials.

Implementation: This project will result in recommendations for different types of advanced curing materials and requirements for the effectiveness of these materials.

Problem Statement 1-3-10. Advancements in Internal Curing of Concrete

In the past few years, IC has evolved into a science. With the advent of lower water-cement ratio mixtures and high-performance concrete, the need for a system to eliminate autogenous shrinkage and self-desiccation has developed, and the use of lightweight fines for the IC of concrete increasingly is being recognized. Internal Curing of Concrete Using Lightweight Aggregate includes a state-of-the-art of practice in this area.(4) In this research, the use of IC for concrete pavement will be explored. The costs and benefits of this technology should be weighed, and a recommendation should be made for proceeding with field trials and other implementation projects.

The tasks include the following:

  1. Identify materials and techniques to promote IC of concrete.

  2. Evaluate the properties of concrete made with these materials including workability, durability, strength, and permeability, as well as the suitability of these materials for concrete pavements.

  3. Conduct laboratory testing to evaluate the effectiveness of IC for concrete paving applications.

  4. Develop recommendations for materials and concrete mixes that will provide IC for concrete pavement applications.

Benefits: IC that will help reduce autogenous shrinkage and self-desiccation and will ensure more complete hydration of cementitious materials, resulting in a less permeable, stronger, and more durable pavement.

Products: Mix design recommendations that will promote IC of concrete pavements.

Implementation: This project will result in material and mix design recommendations that will promote IC of concrete pavements.

Problem Statement 1-3-11. Self-Curing Concrete

Most paving mixtures contain adequate mixing water to hydrate the cement if the moisture is not allowed to evaporate. It should be possible to develop an oil, polymer, or other compound that would rise to the finished concrete surface and effectively seal the surface against evaporation. Dhir et al. recently published some test results on self-curing mixtures.(5) This research will further explore the potential of self-curing concrete.

The tasks include the following:

  1. Identify materials or techniques for developing self-curing concrete.

  2. Evaluate the suitability of these materials for concrete pavement applications, considering workability, strength, permeability, and durability.

  3. Conduct laboratory testing or field trials to evaluate the effectiveness of self-curing concrete for paving applications.

  4. Develop recommendations on materials and techniques for self-curing concrete pavements.

Benefits: Self-curing concrete pavements that will reduce dependence on the contractor to apply adequate curing measures to new concrete pavement and more complete hydration of the cementitious materials, resulting in stronger, less permeable, and more durable concrete pavements.

Products: Recommendations on materials and techniques for constructing self-curing concrete pavements.

Implementation: This project will result in recommendations on materials and techniques for constructing self-curing concrete pavements.

Problem Statement 1-3-12. Cement Containing Titanium Dioxide

To help reduce air pollution and prevent the discoloration of urban concrete surfaces, several cement companies have marketed cement containing a photocatalyst (titanium dioxide), which removes polluting VOCs from the atmosphere and converts them to carbon dioxide. If put into widespread use, such cement could potentially improve urban air quality (e.g., reduce smog), since the amount of carbon dioxide produced would be much smaller than the amount of carbon dioxide from combustion sources. The use of cementitious materials containing photocatalysts is an innovative and profitable way to eliminate pollutants, particularly in urban areas. Concrete pavement would be an ideal application for such a product, as the pavement could decrease the smog produced by the vehicles traveling over the pavement.

The tasks include the following:

  1. Identify concrete mixes containing titanium dioxide that have been shown to remove VOC air pollutants.

  2. Identify the properties of these mixes and evaluate their suitability for concrete pavement applications.

  3. Conduct laboratory testing or field trials to evaluate the effectiveness of these mixes for reducing pollution.

  4. Develop recommendations for using titanium dioxide concrete mixes for concrete paving mixes.

Benefits: Concrete pavements containing titanium dioxide that can potentially remove certain VOCs from the air, helping reduce air pollution in urban areas.

Products: Recommendations for the use of cement containing titanium dioxide in concrete paving mixes.

Implementation: This project will result in recommendations for the use of cement containing titanium dioxide in concrete paving mixes.

Problem Statement 1-3-13. Evaluation of Non-Portland Cementitious Materials

Economic and environmental pressures are encouraging the development of cementitious materials that are not PCC-based systems. Owners will be reluctant to accept such materials unless they can be assured that the materials will provide the performance they require. Current specifications are based on the many years of experience gained in working with portland cements and tend to be more prescriptive than performance based. If innovative materials are to be evaluated the following are required:

The tasks include the following:

  1. Review required performance characteristics.

  2. Select test methods to measure these characteristics.

  3. Select appropriate limits.

  4. Develop specifications.

  5. Develop and present education programs.

Benefits: Ability to rapidly evaluate and accept innovative materials as they become available, thus improving sustainability of concrete pavements.

Products: Performance-based protocols and specifications for cementitious materials.

Implementation: This work will be implementable immediately.

SUBTRACK 1-4. MATERIALS PROPORTIONING

This subtrack specifically addresses proportioning of materials for concrete pavement mix design. Problem statements in this track will integrate volumetrics-based, property-based, performance-based, and functionally based mix designs and recycled materials into the mix design system. Table 5 provides an overview of this subtrack.

Table 5. Subtrack 1-4 overview.
Problem Statement Estimated Costs Products Benefits
1-4-1. Portland Cement Concrete Pavement Mix Design System Integration Stage 1: Volumetrics-Based Mix Design (Mix Proportioning) $500,000–
$1 million
Software, guidelines, and supporting products for a new generation of concrete mix design that will optimize concrete mixtures for paving. A procedure to allow job-specific optimization of concrete paving mixtures based largely on currently available technology
rather than current mix proportioning methods based on either previous experience or procedural guidance developed for a broad range
of concretes.
1-4-2. Portland Cement Concrete Pavement Mix Design System Integration Stage 2: Property-Based Mix Design $1–$2 million Updates to the software, guidelines, and supporting products for concrete mix design and optimization. Building on the foundational work conducted under 1-4-1, a procedure capable of designing and optimizing a mix for more specific and pertinent concrete properties, possibly including strength, workability, permeability, stiffness, shrinkage, and coefficient of thermal expansion.
1-4-3. Portland Cement Concrete Pavement Mix Design System Integration Stage 3: Performance-Based Mix Design $1–$2 million Updates to the software, guidelines, and supporting products for concrete mix design and optimization. A quantum improvement to the mix design process and newly developed tests and models for predicting pavement performance that allow the mix to be
optimized to meet the service requirements of structural and material performance.
1-4-4. Portland Cement Concrete Pavement Mix Design System Integration Stage 4: Functionally Based Mix Design $1–$2 million Updates to the software, guidelines, and supporting products for concrete mix design and optimization. A sophisticated optimization system capable of selecting the most appropriate mixture to meet both performance requirements, as well as functional requirements and a procedure based on new test procedures that identify the potential for concrete to provide a smooth, safe, and quiet pavement.
1-4-5. Integrating Recycled Materials into Portland Cement Concrete Mix Design System $500,000–
$1 million
Guidance and possible modifications to the mix design products that allow a user to design a concrete mixture using recycled materials. Mix design procedures capable of economically and accurately characterizing recycled materials as concrete constituents and facing the challenge of moving to a
100 percent reuse policy, as many countries outside of the United States are doing, particularly in Europe.
1-4-6. Aggregate Models for Optimizing Portland Cement Concrete Mixtures $250,000–$500,000 Thoroughly documented models, also in computerized form, that can be used to optimize the sizing and blending of aggregate stockpiles for a concrete mix. Models that optimize the aggregate structure within a concrete mix that have been shown to improve a wide variety of fresh and hardened concrete properties.

Problem Statement 1-4-1. Portland Cement Concrete Pavement Mix Design System Integration Stage 1: Volumetrics-Based Mix Design (Mix Proportioning)

Today’s mix design for concrete paving mixtures relies on experience, often in the form of recipe mixes. While this experience should not be ignored, the specific mixture used in a particular job should not be considered ideal for every job of that type. There can be a wide range of demands on paving jobs (e.g., required time of opening and use of admixtures and SCMs). Optimization techniques are necessary to select the most appropriate mixture that balances these job-specific conditions with long-term durability while remaining cost effective.

The first step for successfully implementing a mix design system is to develop one that includes methods and parameters with which the industry is familiar. Volumetric-based design (proportioning) includes procedures that specify contents (e.g., minimum cement) and ratios (e.g., water-cement mix) for concrete-making constituents. The guidance given in ACI committee 211 documents might serve as a starting point for newer methods, supplemented with state-of-the-art proportioning guidance advanced by individuals such as J.M. Shilstone and K.C.(6) Hover and by agencies including the National Institute of Standards and Technology  and the U.S. Army Corps of Engineers (USACE), among others. This first stage of the mix design system will employ commonly used lab tests and will limit mix parameter modeling, relying instead on the empirical relationships between mix volumetrics and concrete properties of interest (e.g., strength, workability, and permeability).

The tasks include the following:

  1. Identify and assemble available mix design and proportioning systems.

  2. Assess user needs for the mix design system and determine ways to incorporate the state of the practice to implement this first stage of the overall system quickly.

  3. Assemble the requisite models for the system.

  4. Identify the requisite laboratory test procedures and ensure standardized reporting for input to the mix design system.

  5. Develop a beta version of the system and solicit peer review.

  6. Develop a final version of the system and prepare it for training and implementation.

Benefits: A procedure to allow for job-specific optimization of concrete paving mixtures based largely on currently available technology, rather than current mix proportioning methods based on either previous experience or procedural guidance developed for a broad range of concretes.

Products: Software, guidelines, and supporting products for a new generation of concrete mix design that will optimize concrete mixtures for paving.

Implementation: This first stage of the mix design system will be implementable immediately and will advance the industry. Further refinements will be made to this system in subsequent stages to capture mix properties and pavement performance more directly.

Problem Statement 1-4-2. Portland Cement Concrete Pavement Mix Design System Integration Stage 2: Property-Based Mix Design

While the first stage of the mix design system is based on volumetric ratios and limits, the second stage will offer a more fundamental approach to mix design by measuring and predicting mix properties relevant to pavement performance. The specific properties will be identified when the system itself is developed, and fresh properties (such as rheology) and hardened properties (such as strength and permeability) will be included as targets. The result of the second stage will be a mix design system built on the framework established in the first stage. By using a common interface and process, implementation of this and subsequent stages will be seamless.

The tasks include the following:

  1. Assemble the requisite models for the system.

  2. Identify the requisite laboratory test procedures and ensure standardized reporting for input to the mix design system.

  3. Develop a beta version of the system and solicit peer review.

  4. Develop a final version of the system and prepare it for training and implementation.

Benefits: Building on the foundational work conducted under 1-4-1, a procedure capable of designing and optimizing a mix for more specific and pertinent concrete properties, possibly including strength, workability, permeability, stiffness, shrinkage, and coefficient of thermal expansion.

Products: Updates to the software, guidelines, and supporting products for concrete mix design and optimization.

Implementation: This second stage of the mix design system will be implementable immediately and will advance the industry. Further refinements will be made to this system in subsequent stages to capture pavement performance more directly.

Problem Statement 1-4-3. Portland Cement Concrete Pavement Mix Design System Integration Stage 3: Performance-Based Mix Design

Volumetric- and property-based mix design procedures cannot describe PCC paving mixtures accurately in terms of the mixtures’ impact on pavement performance. The result of these approaches, largely based on an empirical understanding of the effects of properties on performance, is poor design reliability. To offset this shortcoming, this third stage in developing a mix design system will integrate sophisticated pavement performance models. The result will be a seamless tool that can predict various performance measures of a concrete pavement as a function of the concrete mix. Optimization techniques can be used to select the ideal materials and proportions for achieving the desired level of pavement performance while maintaining desired levels of other concrete properties (e.g., strength and workability).

The tasks include the following:

  1. Assemble the requisite models for the system.

  2. Identify the requisite laboratory test procedures and ensure standardized reporting for input to the mix design system.

  3. Develop a beta version of the system and solicit peer review.

  4. Develop a final version of the system and prepare it for training and implementation.

Benefits: A quantum improvement to the mix design process and newly developed tests and models for predicting pavement performance that allow the mix to be optimized to meet the service requirements of structural and material performance.

Products: Updates to the software, guidelines, and supporting products for concrete mix design and optimization.

Implementation: This third stage of the mix design system will be implementable immediately and will advance the industry. Further refinements will be made to this system in subsequent stages to capture the functional performance of the concrete pavement more directly.

Problem Statement 1-4-4. Portland Cement Concrete Pavement Mix Design System Integration Stage 4: Functionally Based Mix Design

Pavement and materials engineering decisions are often driven by functional requirements responding to a public need (e.g., demands for quieter, smoother, and safer pavements). While concrete pavements can meet all of these functional demands, pavements must be designed appropriately to do so. As part of this fourth stage, a system will be developed to evaluate the effects of concrete materials and mixture on pavement function (e.g., noise, ride quality, and texture). By better understanding these relationships, a more rational approach to meeting these functional requirements can be met with improved mix design techniques. Using these procedures, innovative solutions such as two-lift pavements can be designed optimally, with the top layer designed to meet a set of functional demands.

The tasks include the following:

  1. Assemble the requisite models for the system.

  2. Identify the requisite laboratory test procedures and ensure standardized reporting for input to the mix design system.

  3. Develop a beta version of the system and solicit peer review.

  4. Develop a final version of the system and prepare it for training and implementation.

Benefits: A sophisticated optimization system capable of selecting the most appropriate mixture to meet both performance and functional requirements and a process based on new test procedures that identify the potential for concrete to provide a smooth, safe, and quiet pavement.

Products: Updates to the software, guidelines, and supporting products for concrete mix design and optimization.

Implementation: This final stage of the mix design system will be implementable immediately. It is the final product from this research track.

Problem Statement 1-4-5. Integrating Recycled Materials into Portland Cement Concrete Mix Design System

Previous studies have demonstrated that recycled concrete and other recycled materials can be used in new concrete mixtures successfully, as long as the effects of using recycled materials in the mixture are compared to the effects of using virgin materials. This study will build on that work, determining innovative ways to use recycled materials in PCC pavements. Because sustainability is being emphasized increasingly in the United States and abroad, identifying creative uses for recycled materials will sustain and likely extend their desirability.

The tasks include the following:

  1. Investigate using recycled materials in mix designs for shorter performance life pavements, such as an 8-year pavement.

  2. Investigate using recycled materials for various portions of the product (e.g., the fine or course fractions of the aggregate).

  3. Investigate the boundaries for using recycled materials in bases and two-lift construction.

  4. Combine the recommended guidance into supplements or adjustments to the new performance-based mix design system.

Benefits: Mix design procedures capable of economically and accurately characterizing recycled materials as concrete constituents and facing the challenge of moving to a 100 percent reuse policy, as many countries outside of the United States are doing, particularly in Europe.

Products: Guidance and possible modifications to the mix design products that allow users to design a concrete mixture using recycled materials.

Implementation: With pressure to use recycled materials expected to increase, having proper guidance available to users will ensure that the PCC pavement industry is prepared to meet these demands.

Problem Statement 1-4-6. Aggregate Models for Optimizing Portland Cement Concrete Mixtures

Aggregate packing is an important consideration for optimizing concrete mixtures. It is used to determine the optimal proportions of aggregate for a specific concrete mix, given the aggregates available for a particular project. The goal of aggregate packing is to minimize the voids in the aggregate skeleton, thereby minimizing the amount of cement paste needed. This not only strengthens the mix by maximizing the amount of aggregate, but it also minimizes shrinkage, permeability, and porosity.

Additionally, minimizing the amount of cement paste reduces the cost of the mix, as cementitious materials are generally the most expensive component in concrete mixes. Research is needed to develop a method for characterizing the aggregate packing behavior in a concrete mixture based on the aggregate shape and gradation.

The tasks include the following:

  1. Identify existing models suitable for predicting the optimum aggregate structure within a concrete mixture.

  2. Determine the suitability of the existing models for paving mixtures and conduct research to make necessary adjustments.

  3. Develop a beta version of the model through a stand-alone interface and evaluate the predictions against lab and field data.

  4. Develop the final model in a form suitable for rapid incorporation into the mix design system.

Benefits: Models that optimize the aggregate structure within a concrete mix that have been shown to improve a wide variety of fresh and hardened concrete properties.

Products: Computerized models that can be used to optimize the sizing and blending of aggregate stockpiles for a concrete mix and model documentation.

Implementation: The model developed under this effort will be used in the various predictive modes of the mix design system.

SUBTRACK 1-5. MIXTURE EVALUATION

This subtrack identifies all of the new and upgraded equipment and test procedures needed for the concrete laboratory of the future. This subtrack also addresses a range of opportunities, from improved laboratory mixing to more accelerated durability testing. It includes an expert system that connects the test results, as well as equipment purchase assistance and mobile concrete laboratory programs to help facilitate the implementation of test procedures. Table 6 provides an overview of this subtrack.

Table 6. Subtrack 1-5 overview.
Problem Statement Estimated Cost Products Benefits
1-5-1. Laboratory Mixer to Replicate Portland Cement Concrete Field Batching $1–$2 million AASHTO-formatted specifications for constructing and operating a laboratory mixer capable of replicating the full-scale batching and mixing process. Lab equipment capable of simulating the full-scale batching process, resulting in more representative concrete test specimens and a more reliable mix design.
1-5-2. Laboratory Compactor to Replicate Concrete Paving Practice $1–$2 million AASHTO-formatted specifications for constructing and operating a laboratory compactor capable of replicating the full-scale compacting (consolidating) effort induced by the vibration and extrusion process of a slipform paver. Lab equipment capable of simulating the compacting effort of a slipform paver, resulting in more representative concrete test specimens, providing a more reliable mix design.
1-5-3. Test Methods to Assess Concrete Performance at Point of Delivery $1–$2 million Performance-based protocols and specifications for cementitious materials. Ability to rapidly evaluate and accept innovative materials as they become available, thus improving sustainability of concrete pavements.
1-5-4. Statistical Approaches to Mixture Evaluation and Acceptance $500,000–
$1 million
Protocols and specifications for cementitious mixtures, including statistically based pass/fail criteria. Ability to use a rational approach to setting and enforcing limits on test data.
1-5-5. Portland Cement Concrete Mix Durability Tests $2–$5 million Various AASHTO-formatted materials specifications and test procedures capable of evaluating the durability of concrete mixtures. Test procedures that will identify the potential of durability-related problems in the laboratory during mix design and in the field during placement. Alleviation of durability-related issues, ranging from ASR to freeze-thaw durability, including numerous chemical and mechanical distress mechanisms.
1-5-6. Portland Cement Concrete Mix Compatibility Tests $2–$5 million Various AASHTO-formatted test procedures capable of identifying compatibility problems within a mixture or between the mixture and the paving environment. Practical and accurate test procedures for identifying incompatibilities that will reduce cost and improve concrete paving performance; avoiding the increasing possibility of incompatibility from newer constituents added to concrete mixtures, as well as conditions during placement, such as climate.
1-5-7. Portland Cement Concrete Mix Property Test Development $2–$5 million Various AASHTO-formatted test procedures capable of quickly measuring concrete mix properties in a repeatable and reproducible fashion. New test procedures for measuring concrete mix properties that constitute a critical component of the mix design system, providing the data necessary by the models for optimization.
1-5-8. Portland Cement Concrete Mix Thermal Tests $500,000–
$1 million
AASHTO-formatted test procedures for measuring critical thermodynamic properties of a concrete mix, including calorimetry and thermal transport properties. Test procedures for thermal properties of concrete mixes that allow the industry to quantify the impact that the hydration process has on both the early-age behavior and long-term performance of the concrete pavement.
1-5-9. Portland Cement Concrete Mix Performance Testing Equipment $2–$5 million AASHTO-formatted test procedures for new equipment (or a combination of existing equipment) capable of assessing the performance potential of a concrete mix (e.g., susceptibility to fatigue cracking or spalling). Increased concrete pavement quality through tracking the properties that are the most relevant to concrete pavement performance.
1-5-10. Portland Cement Concrete Mix Functional Testing Equipment $2–$5 million AASHTO-formatted test procedures for new equipment (or a combination of existing equipment) capable of assessing the performance potential of a concrete mix (e.g., ability to construct a smooth, safe, and quiet surface). Increased concrete pavement quality through tracking the properties that are the most relevant to concrete pavement performance.
1-5-11. Expert System for Portland Cement Concrete Mixes $1–$2 million A robust computerized expert system with an intuitive interface that allows users to access best practices and to troubleshoot. Preservation of institutional memory, which is fading as many industry experts retire;
an expert system that captures their experience in a form that is easily accessible to anyone.
1-5-12. Support for Federal Highway Administration Mobile Concrete Laboratory Demonstrations $1–$2 million A series of conferences and workshops that present the proper use of the new mix design system along with a background of the development and further demonstration of the Mobile Concrete Research Laboratory nationwide. A mobile concrete laboratory that allows potential users a firsthand look at available technology, an instrumental component in technology transfer, and demonstrations of the performance-based mix design system along with the requisite laboratory tests.
1-5-13. Portland Cement Concrete Mix Design Equipment for States $1–$2 million Funding for purchasing the equipment recommended for use in the performance-based mix design system. Funding made available to allow State agencies to use the new equipment recommended as part of the mix design system.

Problem Statement 1-5-1. Laboratory Mixer to Replicate Portland Cement Concrete Field Batching

The techniques used to mix concrete in the laboratory differ from field techniques. For example, differences are evident in charging sequences and mixing energy. This research will develop performance specifications for a new generation of laboratory mixers that can better replicate the full-sized mixers commonly used in concrete paving. The cost and efficiency of a laboratory mixer will be considered. If successful, the new laboratory mixer will evaluate new and innovative PCC mix designs more quickly for research, mix development, and QC.

The tasks include the following:

  1. Identify available technologies and previous trials of similar laboratory mixers.

  2. Develop additional technology and equipment as needed.

  3. Compare various concrete mixtures as mixed in full-scale batching operations with those mixed in the new laboratory mixer. Comparisons should be made based on pertinent properties such as air void structure, strength, and permeability.

  4. Develop an AASHTO-formatted standard if a new mixer is successfully identified.

Benefits: Lab equipment capable of simulating the full-scale batching process, resulting in more representative concrete test specimens and a more reliable mix design.

Products: AASHTO-formatted specifications for constructing and operating a laboratory mixer capable of replicating the full-scale batching and mixing process.

Implementation: This technology, if identified, can be a key component of the laboratory of the future that will feed key mix test results into the mix design system.

Problem Statement 1-5-2. Laboratory Compactor to Replicate Concrete Paving Practice

The techniques employed to consolidate laboratory specimens (either in the field or in the lab) do not represent the nature of the concrete in place after paving. Differences in the source and energy of consolidation result in differences in the quantity, position, and orientation of the various concrete constituents within the mixture (particularly the air void structure). This research will develop a consolidation device that can better simulate the consolidation process that results from slipform paving (and other placement techniques as needed).

The tasks include the following:

  1. Identify available technologies and previous trials of similar laboratory compactors.

  2. Develop additional technology and equipment as needed.

  3. Compare various concrete mixtures compacted in place (behind a slipform paver) with mixtures compacted using the new laboratory compactor. Comparisons should be made based on pertinent properties such as air void structure, strength, and permeability.

  4. If a new compactor is identified, develop an AASHTO-formatted standard.

Benefits: Lab equipment capable of simulating the compacting effort of a slipform paver, resulting in more representative concrete test specimens, providing a more reliable mix design.

Products: AASHTO-formatted specifications for constructing and operating a laboratory compactor capable of replicating the full-scale compacting (consolidating) effort induced by the vibration and extrusion process of a slipform paver.

Implementation: This technology, if identified, can be a key component in future laboratories that will feed key mix test results into the mix design system.

Problem Statement 1-5-3. Test Methods to Assess Concrete Performance at Point of Delivery

Current acceptance methods for concrete mixtures delivered to a construction site either do not measure the most critical parameters reliably or take several days or weeks to conduct.

To improve reliability of the as-built pavement, there is a need to develop the following:

The tasks include the following:

  1. Review required performance characteristics.

  2. Select test methods to measure these characteristics.

  3. Select appropriate limits.

  4. Develop specifications.

  5. Develop and present education programs.

Benefits: Ability to rapidly evaluate and accept innovative materials as they become available, improving sustainability of concrete pavements.

Products: Performance-based protocols and specifications for cementitious materials.

Implementation: This work will be implementable immediately.

Problem Statement 1-5-4. Statistical Approaches to Mixture Evaluation and Acceptance

Current acceptance methods for concrete mixtures are based on strength and slump. As more performance-based requirements are imposed on a mixture, methods have to be developed that will account for inherent variation in the mixture and in the test methods utilized. This concept is common when considering strength where a multiplier is applied to a design value and statistical methods are used to confirm the acceptability of a day’s work. However, for other methods, a single pass/fail value is applied. This significantly increases the probability that a good mixture is rejected or a bad mixture is accepted. For instance, if the rapid chloride test is used, a common pass fail limit applied may be 1,500 coulombs (C). A single test result of 1,501 C may be deemed a failure even though the scatter on the test method is about 500 C.

There is a need for a rational approach be developed that takes into account variability when specifying acceptance tests.

The tasks include the following:

  1. Review required performance characteristics and associated tests.

  2. Determine scatter associated with tests.

  3. Develop statistical limits for each test.

  4. Develop and present education programs.

Benefits: Ability to use a rational approach to setting and enforcing limits on test data.

Products: Protocols and specifications for cementitious mixtures, including statistically based pass/fail criteria.

Implementation: This work will be implementable immediately.

Problem Statement 1-5-5. Portland Cement Concrete Mix Durability Tests

Contractors and owner-agencies want to know whether a mix designed to last 30 years or longer will last that long when placed in the field, particularly if the pavement is constructed under a warranty or performance-based specification. It is likely that no single test will be able to guarantee that a pavement will last 30 years or more, largely because of variable environmental conditions and traffic/wheel loading over the life of the pavement. However, it should be possible to develop test methods to predict the probability that a given concrete mix will last for the intended design life. While this broad research will require further definition during the framework stage, many key mix durability characteristics should be investigated as needed, including freeze-thaw durability, ASR resistance, sulfate attack resistance, and steel corrosion potential. Research is needed to develop accelerated testing methods that more accurately predict the long-term strength, durability, and performance potential of concrete. These tests will allow the owner-agency or contractor to evaluate the mix design before construction as well as after placement based on core samples removed from the newly placed pavement. An initial step may require additional research to define the minimum water-cement ratio in the field. Meanwhile, premature materials-related distress in concrete pavements appears to be growing more widespread. As a result, additional investigation is needed to identify the various potential causes of the observed problems. Research is also needed to develop improved sulfate-resistant concretes, especially for paving applications, and a broad program of research is needed to mitigate existing ASR conditions. This task should also address air void and steel corrosion issues.

The tasks include the following:

  1. Identify the various durability issues facing concrete pavements, discerning and linking research that addresses both the visible distresses and the fundamental mechanisms.

  2. Study available equipment and test procedures to identify the potential for and severity of the various deterioration mechanisms as a function of the concrete mix.

  3. Develop and integrate AASHTO-formatted lab test procedures that feed into the mix design system, allowing users to optimize a mix based on material durability and other criteria.

Benefits: Test procedures that will identify possible durability-related problems in the laboratory during mix design and in the field during placement. Other benefits include alleviation of durability-related issues ranging from ASR to freeze-thaw durability and include numerous chemical and mechanical distress mechanisms.

Products: Various AASHTO-formatted materials specifications and test procedures capable of evaluating the durability of concrete mixtures.

Implementation: A suite of tests will result that can be used to identify possible durability issues associated with a given mix design. These tests will provide inputs for the mix design system, as well as other research tracks, including process QC.

Problem Statement 1-5-6. Portland Cement Concrete Mix Compatibility Tests

Mineral and chemical admixtures are currently available for improving the essential properties of a concrete mix (i.e., strength, permeability, and freeze-thaw resistance). However, these admixtures are often used in combination in a PCC paving mix without a thorough understanding of the materials’ interaction or compatibility. For example, while a proper air void system is essential for durable concrete, excessive air voids reduce the effective cross sectional area of concrete elements, decreasing concrete strength. SCMs can cause further complications by creating an unstable air void system in freshly mixed concrete. This problem worsens when certain chemical admixtures are also used in the concrete. Research is needed to study the interaction and compatibility of various admixtures in PCC mixes and the effects that incompatibility may have on concrete properties and pavement performance. Research is also needed to develop accelerated testing methods that more accurately predict incompatibilities and their effects on long-term strength, durability, and performance. These tests will allow the owner-agency or contractor to evaluate the mix design before construction and ensure compatibility of mixture components before concrete placement.

The tasks include the following:

  1. Identify known compatibility problems among PCC admixtures, including the effects admixtures have on concrete properties such as workability and the air void system.

  2. Conduct laboratory testing to identify further compatibility problems.

  3. Determine the effects of incompatible materials on pavement performance.

  4. Determine the limits on proportions of incompatible materials.

  5. Develop AASHTO-formatted test procedures and associated equipment that can identify incompatibilities in concrete mixes in the lab.

  6. Integrate the lab test procedures into the mix design system to allow users to avoid mixture incompatibilities during the mix design process.

Benefits: Practical and accurate test procedures for identifying incompatibilities that will reduce costs and improve concrete paving performance. Other benefits include avoiding the increasing possibility of incompatibility from newer constituents added to concrete mixtures, which is also due to conditions during placement, such as climate.

Products: Various AASHTO-formatted test procedures capable of identifying compatibility problems within a mixture or between the mixture and the paving environment.

Implementation: Guidelines and test procedures/equipment that identify potential incompatible materials in PCC paving mixes will result. These tests can be used during the mix design process as well as for QC during construction.

Problem Statement 1-5-7. Portland Cement Concrete Mix Property Test Development

Mix properties affect both the constructability and long-term performance of PCC pavements. While this broad research will require significant definition during the framework stage, some of the essential mix properties that may warrant investigation include water-cement ratio, permeability, air void system, and workability. While several tests that measure most of these properties currently exist, many of these test procedures are still somewhat crude or time consuming and give varied results. For example, while it is simple to calculate water-cement ratio based on batch weights, this calculation may not accurately indicate the actual water-cement ratio due to the addition of water at the job site, inaccurate estimates of aggregate moisture content, or water evaporation during transportation. Thin sections can be used to estimate the water-cement ratio of the hardened concrete, but this is time consuming and generally occurs long after paving is finished. Research is needed to investigate essential mix properties and develop or further refine procedures for measuring these mix properties quickly and accurately. This research will identify essential mix properties affecting both constructability and pavement performance and develop testing equipment for measuring these properties.

The tasks include the following:

  1. Identify essential mix properties that affect pavement constructability and performance.

  2. Identify and develop AASHTO-formatted test procedures and associated equipment for measuring these properties.

  3. Develop new equipment that can be used to measure essential mix properties in the lab and in the field quickly and accurately.

  4. Develop recommendations for deploying mix property testing equipment.

Benefits: New test procedures for measuring concrete mix properties that constitute a critical component of the mix design system, providing the data necessary by the models for optimization.

Products: Various AASHTO-formatted test procedures capable of quickly measuring concrete mix properties in a repeatable and reproducible fashion.

Implementation: This work will result in test equipment that will quickly and accurately measure essential mix properties. The test equipment can be used for trial batching during the mix design process and for QC during construction.

Problem Statement 1-5-8. Portland Cement Concrete Mix Thermal Tests

The FHWA HIPERPAV® (HIgh PERformance Concrete PAVing) program is among a number of recent initiatives that have underscored the importance of heat development in concrete pavements. A concrete mixture generally can be characterized by a unique signature representing the amount and rate of heat generated through the hydration process. Measuring this characteristic requires a calorimeter commonly isothermal, adiabatic, or semi-adiabatic. While the importance of this concrete characteristic has been demonstrated and accepted, no accepted standard for measurement currently exists. This research will develop a nonproprietary test standard suitable for AASHTO adoption. If both practical and cost effective, the standard should spur widespread acceptance of this test for characterizing a concrete mixture. A second goal in developing the specification should be to develop a test rugged enough for use in the field for routine QC. Finally, if the heat signature test is found to be sensitive to pavement performance, tests for other thermal properties should be developed during this task, including tests for the specific heat and thermal conductivity of the PCC. A precedent currently exists for evaluating these parameters within the MEPDG.(1)

The tasks include the following:

  1. Identify the mix thermal properties that are most sensitive for predicting concrete pavement behavior and performance.

  2. Identify existing lab tests to evaluate the most sensitive properties. Evaluation criteria should include ease of use, proprietary nature, cost, ruggedness, repeatability, and reproducibility.

  3. Select candidate lab tests and perform a structured evaluation of the equipment, comparing the test results to known standards, if possible.

  4. Develop specifications suitable for adoption by AASHTO.

Benefits: Test procedures for thermal properties of concrete mixes that allow the industry to quantify the impact of the hydration process on both the early-age behavior and long-term performance of the concrete pavement.

Products: AASHTO-formatted test procedures for measuring critical thermodynamic properties of a concrete mix, including calorimetry and thermal transport properties.

Implementation: A number of tests will result that can identify the thermal properties of concrete mixes. These tests will provide inputs for the mix design system, as well as other research tracks, including process (quality) control and ICSs.

Problem Statement 1-5-9. Portland Cement Concrete Mix Performance Testing Equipment

Mix performance is one of the most important factors in determining pavement performance, particularly in the long term. Some essential performance properties include freeze-thaw resistance, abrasion resistance, and sulfate-attack resistance, among others. Understanding mix performance will help contractors and owner-agencies develop mixes that meet the design life requirements. Performance problems may not necessarily be caused by durability problems, such as material incompatibility and freeze-thaw resistance, but they may result from improper mixture proportioning or material selection. This research will examine factors that affect mix performance and thereby affect pavement performance. Testing equipment will be developed to help quickly predict mix performance during the mix design process in the laboratory.

The tasks include the following:

  1. Identify factors (e.g., mix proportions and materials) that affect mixture performance.

  2. Identify equipment or test procedures that can be used to predict mix performance.

  3. Refine existing equipment or develop new testing equipment that can be used to quickly predict mix performance.

  4. Work with contractors and owner-agencies to evaluate the test equipment.

  5. Develop AASHTO-formatted specifications and associated recommendations for deploying new testing equipment.

Benefits: Increased concrete pavement quality through tracking the properties that are the most relevant to concrete pavement performance.

Products: AASHTO-formatted test procedures for new equipment (or a combination of existing equipment) capable of assessing the performance potential of a concrete mix (e.g., susceptibility to fatigue cracking or spalling).

Implementation: Testing procedures and equipment that can predict mix performance in the laboratory will result. The testing equipment can be used by contractors and owner-agencies during the mix design process and for QC testing.

Problem Statement 1-5-10. Portland Cement Concrete Mix Functional Testing Equipment

Some properties of PCC mixes can affect the functional performance of PCC pavements, including mix placeability (which affects ride quality and tire-pavement noise), abrasion resistance (which affects ride quality and safety), and skid resistance (which affects safety). These PCC mix properties ultimately influence roadway user satisfaction, particularly regarding users’ safety and driving comfort. While these issues may not affect pavement performance directly, significant consequences can result if they are overlooked. For example, a pavement that is too noisy may require expensive sound walls, while a pavement with poor abrasion resistance may rut under studded tires and require costly rehabilitation. Research is needed to investigate the essential functional properties of PCC paving mixes and develop tests for measuring these properties. The tests should allow the contractor or owner-agency to quickly predict functional performance during the mix design process so adjustments can be made before construction.

The tasks include the following:

  1. Identify important properties of PCC mixes that ultimately tie into functional
    pavement performance.

  2. Identify test procedures and equipment that can be used to measure these properties.

  3. Modify existing equipment or develop new equipment that can quickly and accurately measure the properties that predict pavement functional performance.

  4. Develop AASHTO-formatted specifications and associated recommendations for deploying functional testing equipment.

Benefits: Increased concrete pavement quality through tracking the properties that are the most relevant to concrete pavement performance.

Products: AASHTO-formatted test procedures for new equipment (or a combination of existing equipment) capable of assessing the performance potential of a concrete mix (e.g., susceptibility to fatigue cracking or spalling).

Implementation: This work will result in testing procedures and equipment that can measure mix properties to predict pavement functional performance. The tests can be used during the mix design process and for QC during construction.

Problem Statement 1-5-11. Expert System for Portland Cement Concrete Mixes

Recent concerns about early deterioration of concrete pavement indicate a need for tools that predict concrete durability problems during mixture proportioning and design. No limitations usually exist on the combination of materials that can produce workable and durable concrete. However, constituent materials with certain chemical attributes, such as high levels of alkali, may develop mixture durability problems. Data for long-term tests of concrete mixtures, such as the prism test and screening tests for such constituents as aggregate, are available from many States. Compiling these data into a large database could provide the foundation for an expert system to predict durability problems. This system could indicate the potential for material combination problems and guide engineers and contractors in developing mix designs for pavement projects.

Because of the rapid increase in the number of concrete production materials available, it is important to develop a national database that collects and synthesizes information about all concrete mixes used throughout the United States, from mix design to durability in the field. Clearly documenting the mixes that are successful for a particular application and set of materials and those that are unsuccessful will provide States and others a means to assess their own mixes without having to perform extensive and costly laboratory testing. The database will allow users to determine whether a certain mix design will be successful or unsuccessful. More specifically, this national database will contain information about the concrete materials, mix proportions, locations of use, pavement designs, fresh and hardened concrete properties, construction methods, and the long-term durability performance of the concrete mixes. It will also detail issues such as whether ASR, sulfate attack, freeze-thaw resistance, or any other fresh or hardened concrete property was inappropriate for a particular mixture and site condition.

The tasks include the following:

  1. Identify available sources of information for the expert system, including existing syntheses, expert personnel, and existing databases.

  2. Identify a structure for the expert system that allows users intuitive access to the information and rapid and efficient population of the information during development.

  3. Develop a beta version of the system and establish a peer review process.

  4. Refine the expert system and prepare a form suitable for rapid implementation (e.g., consideration should be made for Internet deployment to keep the system dynamic).

Benefits: Preservation of institutional memory, which is fading as many industry experts retire. Other benefits include a system that captures their experience in a form that is easily accessible.

Products: A robust computerized expert system with an intuitive interface that allows users to access best practices and troubleshoot.

Implementation: An expert system will be developed that includes an extensive database of experience and other data related to paving concrete mixtures and their performance. This information should be kept dynamic with ongoing updates and feedback.

Problem Statement 1-5-12. Support for Federal Highway Administration Mobile Concrete Laboratory Demonstrations

The FHWA Mobile Concrete Laboratory brings the lab to the job site to introduce contractors and owner-agencies to concrete mix design and testing technology. With the development of a new mix design system and new testing equipment and procedures, onsite demonstrations using the Mobile Concrete Laboratory are necessary for introducing this new technology to contractors and owner-agencies. For this purpose, this research will provide funding to send the Mobile Concrete Research Laboratory to various projects throughout the United States.

The tasks include the following:

  1. Identify potential projects and contractors and owner-agencies interested in Mobile Concrete Laboratory demonstrations.

  2. Demonstrate the mix design system and new concrete testing equipment at these project locations.

Benefits: A mobile concrete laboratory that allows potential users a firsthand look at available technology, an instrumental component in technology transfer, and demonstrations of the performance-based mix design system along with the requisite laboratory tests.

Products: A series of conferences and workshops that presents the proper use of the new mix design system along with a background of the development and further demonstration of the Mobile Concrete Laboratory nationwide.

Implementation: This research will provide continued funding for sending the Mobile Concrete Laboratory to PCC paving projects throughout the country.

Problem Statement 1-5-13. Portland Cement Concrete Mix Design Equipment for States

Most States lack the funding necessary to purchase their own new and advanced equipment. Moreover, many contractors are reluctant to invest large amounts of capital in new equipment unless they are sure it will be profitable. Therefore, a vehicle that helps States purchase needed equipment should be established to promote such equipment for mix design testing.

Task: Establish requirements for helping States purchase advanced equipment to test mix designs.

Benefits: Funding made available to allow State agencies to use the new equipment recommended as part of the mix design system.

Products: Funding for purchasing the equipment recommended for use in the performance-based mix design system.

Implementation: This work will result in a vehicle that helps States purchase advanced equipment for PCC pavement mix design testing.

SUBTRACK 1-6. POST-CONSTRUCTION PAVEMENT MATERIALS EVALUATION

This subtrack will address the evaluation of materials for the concrete pavement after construction. This includes materials such as dowel bars, tie-bars, reinforcing steel, joint materials, and curing compounds. Table 7 provides an overview of this track.

Table 7. Subtrack 1-6 overview.
Problem Statement Estimated Cost Products Benefits
1-6-1 Evaluation of Innovative Materials for Use as Dowels, Tie-Bars, and Reinforcing Steel $400,000 Recommendations for use of innovative reinforcing systems. Reduced cost of failure of steel-based materials.
1-6-2 Evaluation of Innovative Materials for Use as Jointing Materials $750,000 Recommendations for use of sealants. Reduced cost of failure of joint sealants.
1-6-3 Evaluation of Innovative Materials for Curing $1 million Recommendations for curing. Improved longevity of concrete surface.

Problem Statement 1-6-1. Evaluation of Innovative Materials for Use as Dowels, Tie-Bars, and Reinforcing Steel

Corrosion of steel-based elements used in pavements can be a significant source of distress in pavements. Work is needed to investigate, assess, and implement the use of materials that are less prone to corrosion, either by providing protection to the steel or by replacing it.

The tasks include the following:

  1. Review available materials.

  2. Assess acceptability of systems.

  3. Develop guidelines.

  4. Publish guidelines.

Benefits: Reduced cost of failure of steel based materials.

Products: Recommendations for use of innovative reinforcing systems.

Implementation: Implement recommendations developed.

Problem Statement 1-6-2. Evaluation of Innovative Materials for Use as Jointing Materials

The purpose of sealants in joints is to prevent water penetration and to ingress of incompressibles. Currently available jointing materials require regular maintenance or they need to be replaced periodically. There is a need to develop longer lasting materials that provide equivalent or better protection to the joints. There is also a need to develop guidelines for the use of such materials in the variety of applications and environments encountered across the United States.

The tasks include the following:

  1. Investigate methods to improve performance of sealants.

  2. Investigate methods to improve longevity of sealants.

  3. Assess acceptability of new systems.

  4. Develop guidelines.

  5. Publish guidelines.

Benefits: Reduced cost of failure of joint sealants.

Products: Recommendations for use of sealants.

Implementation: Implement recommendations developed.

Problem Statement 1-6-3. Evaluation of Innovative Materials for Curing

 


The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
FHWA
United States Department of Transportation - Federal Highway Administration