Long-Term Plan for Concrete Pavement Research and Technology - The Concrete Pavement Road Map: Volume II, Tracks

Track 12. Advanced Concrete Pavement Materials (AM)

TRACK 12 (AM) OVERVIEW

If the concrete pavement industry continues to use the same types of materials, the same problems and limitations will persist in concrete pavement applications. Fortunately, innovative concrete paving materials continually are being developed to enhance performance, improve construction, and reduce waste. The problem statements in this track will develop new materials and refine or introduce existing advanced materials. Many existing materials that the problem statements study have been used thus far only on a small scale, such as in laboratory tests. Most existing materials have not been used in the United States, but have been used successfully in other countries. This track will bring new concrete paving materials into common practice by experimenting with them on a larger scale and developing standards and recommendations for their use. Moreover, this research will foster innovation in the development of new and innovative concrete pavement materials.

The problem statements in this track are grouped into three subtracks: performance-enhancing, construction-enhancing, and environment-enhancing concrete pavement materials. Performanceenhancing materials will improve pavement durability and long-term performance, perhaps extending pavement life further than conventional materials. Construction-enhancing materials will improve the construction process by reducing material requirements, labor requirements, or construction time. Finally, environment-enhancing materials show promise not only by reducing waste through pavement reclamation, but also for reducing raw consumer and industrial waste. Clearly, many of these materials fit into more than one category. A material that improves the construction process, for example, also may improve pavement durability and performance. Likewise, a material that uses consumer waste also may improve pavement performance.

The emphasis on environment-enhancing materials is significant. Not only are contractors and agencies paying heavily to dispose of reclaimed asphalt and concrete pavement, but also other industries are looking for environmentally responsible ways to dispose of industrial and consumer waste to reduce the burden on landfills. Environmental concerns are expected to become more important in the next few decades as landfills quickly fill.

The following introductory material summarizes the goal and objectives for this track and the gaps and challenges for its research program. A chart is included to show an overview of the subtracks and problem statements in the track. 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 Goal

New materials will be evaluated and existing materials will be refined to improve concrete pavement performance, enhance construction, and lessen environmental impact.

Track Objectives

1. Improve pavement durability and long-term performance to extend pavement life further than conventional materials.
2. Improve the construction process by reducing material requirements, labor requirements, or construction time.
3. Reduce waste through pavement reclamation.

Research Gaps

• Lack of understanding of how advanced materials impact concrete pavement performance, construction, and the environment.
• Limited full-scale testing of new and innovative materials.

Research Challenges

• Experiment with advanced concrete pavement materials on a larger scale than previously done.
• Developing standards and recommendations for the use of advanced concrete pavement materials.
• Foster innovation in the development of new and innovative concrete pavement materials.

Research Track 12 (AM) Phasing

The horizontal bar chart in figure 12 shows the problem statements in this track grouped by subtrack. Because this track is unphased, no time phasing is shown.

Click to enlarge or view alternative text

Figure 12. Track 12 (AM) unphased subtrack and problem statement chart.

Research Track 12 (AM) Estimated Costs

Table 58 shows the estimated costs for this research track.

Track Organization: Subtracks and Problem Statements

Track 12 (AM) problem statements are grouped into three subtracks:

• Subtrack AM 1. Performance-Enhancing Concrete Pavement Materials.
• Subtrack AM 2. Construction-Enhancing Concrete Pavement Materials.
• Subtrack AM 3. Environment-Enhancing Concrete Pavement Materials.

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 follow.

SUBTRACK AM 1. PERFORMANCE-ENHANCING CONCRETE PAVEMENT MATERIALS

The innovative materials developed in this subtrack may meet requirements that conventional concretes do not meet as efficiently. The materials developed are specialty concrete varieties for specific, unique applications. Table 59 provides an overview of this subtrack.

Problem Statement AM 1.1. Flexible Cementitious Overlay Materials

The majority of HMA pavements ultimately will fail due to rutting. Increased axle loads, higher tire pressures, and increasing traffic volume contribute to this problem; today, more than 90 percent of roads are being overloaded. Developing a cementitious overlay material that can be used as a strengthening and wearing course on flexible pavements, even when applied in thin layers, would be extremely useful. Ductility of the material is obtained through controlled microcracking and fiber reinforcement. A major project is currently underway in the European Union to look at porous polymer concretes. Several different compositions such as this could be used, resulting in the selection of a few types to be used for full-scale testing as overlays on appropriate highways. A similar project could be conducted in the United States that builds on the information and results from the European Union project. Design criteria and draft specifications for the use of the new material will be a part of the project results.

Tasks:

1. Identify required properties for thin overlays.
2. Identify existing materials used for thin cementitious overlays.
3. Modify existing materials or develop new materials for thin overlays, if necessary.
4. Develop field trials or accelerated load testing of overlay materials.
5. Develop design criteria, specifications, and construction procedures for use of cementitious overlay materials.

Problem Statement AM 1.2. 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 then could 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 understanding of the impacts that fibers can play on load transfer (as compared to dowels and tie bars).

Tasks:

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.

Problem Statement AM 1.3. 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 11.4 to 18.9 liters (3 to 5 gallons) 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. Most of the pervious pavements constructed thus far, however, 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.

Tasks:

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, 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.

Problem Statement AM 1.4. 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 supplementary cementitious materials. With further research, this process likely could lead to the development of new materials from novel waste streams and accelerate the development of new and improved concrete mixtures.

Tasks:

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.

Problem Statement AM 1.5. Reactive Powder Concretes as Ductile Materials

With a technological breakthrough at the beginning of the 1990s, RPC offered compression strengths in excess of 200 megapascals (MPa) (29,000 pounds-force per square inch (psi)), flexural strengths of over 40 MPa (5,800 psi), and ductility. Ductal^® and BSI^®, two products of the RPC family developed in France, are considered ultrahigh-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.

Tasks:

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.

Problem Statement AM 1.6. Chemically Bonded Ceramic

Chemically bonded phosphate ceramic (Ceramicrete) is a type of concrete with very low permeability. Ceramicrete is formed when magnesium oxide powder and soluble phosphate powder (both available, low-cost materials) are mixed with water, creating a nonporous material with compressive strength higher than that of concrete. Ceramicrete can be made with commercially available equipment that mixes the powder components into the binder. "The wet material (binder, aggregates, and water mixture) can then be pumped, gunned, or sprayed, also with commercially available equipment."⁽⁶⁾ The feasibility (costs and benefits) of using Ceramicrete for concrete paving should be explored.

Tasks:

1. Identify Ceramicrete mixes and their properties (strength, permeability, workability, long-term durability) and cost.
2. Evaluate the feasibility of using Ceramicrete for concrete pavement construction, considering constructability, durability, and cost.
3. Develop recommendations for using Ceramicrete in concrete paving applications, including repairs, overlays, and new construction.

Problem Statement AM 1.7. 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 thus 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.

Tasks:

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 highquality materials at the joints.

Problem Statement AM 1.8. 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.

Tasks:

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.

SUBTRACK AM 2. CONSTRUCTION-ENHANCING CONCRETE PAVEMENT MATERIALS

The materials developed under this subtrack address specific constructability issues and provide creative alternatives to conventional concrete. The problem statements in this subtrack will develop special concrete materials for use in various concrete paving applications. Table 60 provides an overview of this subtrack.

Problem Statement AM 2.1. Application of Self-Consolidating Concrete for Concrete Paving

Significant interest in recent years has arisen over the use of 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.

Tasks:

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.

Problem Statement AM 2.2. Applying Very High-Strength Concrete to Pavement Operations

High-strength concrete currently is being used in rapid-cure patches. However, the high cement content causes high temperatures that can result in thermal contraction problems. At present, early opening is the only advantage to using high-strength concrete in pavements. Also, such concrete is expensive, and if high-strength pavements are to be competitive, ways to minimize the amount of the expensive concrete must be found. The French have developed a two-layer extruded slipform operation that encapsulates normal concrete within a protective high-strength concrete. Other more economical options also might be considered, such as slabs cast with internal voids, or beam and slab configurations, although data is needed on deflection, water movement, friction, curling, and warping of unusual slab configurations. Jointing technology also would be needed. A vigorous research study would be needed to make using 69 MPa (10,000 psi) concrete more efficient for structural pavements.

Just as continuously welded rails are used, it should be possible to construct a continuous ribbon of concrete that would withstand a temperature range of 55 ^°C (100 ^°F). A tensile strength of about 17 MPa (2,500 psi) would be needed, which might be possible with a compressive strength of about 172 MPa (25,000 psi) (plus a factor of safety). This could be accomplished with polymer impregnation if a field process could be developed. For comparison, a laboratory strength of about 731 MPa (106,000 psi) has been attained with PCC. Special concretes currently are being used in the 172 MPa (25,000 psi) range, based on a reactive powder process. The strength must be attained about 18 hours before the concrete begins to cool and contract. Of course, such continuous ribbons of ultrahigh-strength concretes will experience about 50 mm (2 inches) of movement at the ends, making special anchors or joints necessary.

Tasks:

1. Identify high-strength mixes and the properties (i.e., strength, shrinkage, and workability) of these mixes.
2. Determine the suitability of these mixes for paving applications based on these properties.
3. Modify existing mixes or develop new mixes to meet paving requirements.
4. Identify construction requirements (i.e., special curing procedures) for using high-strength mixes for pavements.
5. Identify alternative paving techniques (e.g., voided or hollow slabs) to reduce the quantity and cost of using high-strength mixes.
6. Conduct lab testing and/or field trials of high-strength pavements.
7. Develop mix design recommendations, construction procedures, and specifications for high-strength concrete pavements.

Problem Statement AM 2.3. Dry-Laid Concrete

New formulations and procedures have been developed that enable concrete to be placed as a cementitious dry mix that is then watered from above to produce a strong, thin slab or pavement. The need for onsite mixing is eliminated. In the field, the strength of dry-laid slabs only 10 to 50 mm (0.39 to 1.95 inches) thick saves raw materials and excavation costs and may make resurfacing old concrete a practical possibility. Dry-laid materials are also easier to work with than conventional moist or semidry concrete screeds, and should result in a stronger and more durable end product.

Preliminary tests indicate that strong concrete substantially free of shrinkage cracking can be produced by dry-laid methods using premixed materials in which the maximum particle size is limited, typically to 5 mm (0.2 inch) in diameter. The absence of large particles means that thinner slabs of concrete down to 10 mm (0.39 inch) can be laid. Although the mixture has a higher cement and fines content than conventional concrete, the dry-laid process reduces the problem of self-induced cracking due to drying shrinkage that generally is encountered with cement-rich mortars laid as a wet mix. Although the product originally was conceived as an easy-to-use, do-it-yourself surfacing product, there appears to be a major opportunity to apply it to concrete paving. Innovative aspects of dry-laid techniques include:

• Need for mixing onsite eliminated; more easily placed than wet or semidry mixes; factory-mixed precision carried through to final placement; problems of premature setting avoided.
• The strength of concrete and the thinness of mortars or screeds combined; readily compatible with the delivery of dry mixes in silos and mechanized placement.
• Early resistance to traffic.
• Convenient material for patching repairs and extensive resurfacing of old concrete as well as new pavements.
• Attractive surface finishes can be incorporated; economical to produce.

Tasks:

1. Identify dry-laid concrete materials, techniques, and previous applications.
2. Identify required properties for dry-laid concrete for PCC pavements and benefits of using dry-laid concrete over conventional wet construction.
3. Identify materials and techniques for dry-laid concrete that will meet the requirements for PCC pavements.
4. Perform laboratory testing and/or field trials to evaluate the viability of dry-laid concrete for pavements.
5. Develop design recommendations and construction procedures for using dry-laid concrete for overlays, repairs, and new construction.

Problem Statement AM 2.4. Energetically Modified Cement

One important constraint of using cement blended with various pozzolanic or cementitious substances (e.g., fly ash, 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.

Tasks:

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

Problem Statement AM 2.5. 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.

Tasks:

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.

Problem Statement AM 2.6. Cold Weather Concreting Advancements

USACE researchers are experimenting with concrete admixtures that allow for subzero pours as low as -15 ^°C (5 ^°F) in the open air. Underwritten by 10 State DOTs, the 3-year, $750,000 program is paving the way for reduced labor in winter months and a longer construction season. The team is working with combinations of off-the-shelf products to lower the freezing temperature of concrete. These substances, which commonly are available to contractors, include concrete accelerators, corrosion inhibitors, and plasticizers already governed by their own set of standards. One recent study involved a 32-m (104-ft)- long bridge curb in Lebanon, NH. The result of using the laboratory’s experimental concrete was a savings of 132 labor hours needed to build an enclosure and $50 in liquid propane. The total cost was $700, rather than $750 plus labor for traditional methods. The next step is to develop a recipe guide for admixture chemicals. Beyond this, research still is needed to demonstrate the benefits of this technology for concrete pavements.

Tasks:

1. Identify materials and concrete mixtures that permit concrete placement in subzero conditions without special measures to protect the concrete.
2. Evaluate the properties of these materials and the viability of their use in concrete pavements.
3. Conduct laboratory or field trials of cold weather concretes for paving projects.
4. Evaluate the cost versus benefits of cold weather concretes, giving consideration to extending the construction season and reducing cold weather construction labor.
5. Develop recommendations for cold weather pavement mixes and construction and curing procedures.

Problem Statement AM 2.7. 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 selfdesiccation has developed, and the use of lightweight fines for the IC of concrete increasingly is being recognized. The paper, "Internal Curing of Concrete Using Lightweight Aggregate" includes a state of the art of practice in this area.⁽⁷⁾ 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 made for proceeding with field trials and other implementation projects.

Tasks:

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, and 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.

Problem Statement AM 2.8. 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. R.K. Dhir et al. recently published some test results on self-curing mixtures.⁽⁸⁾ This research will explore further the potential of self-curing concrete.

Tasks:

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.

SUBTRACK AM 3. ENVIRONMENT-ENHANCING CONCRETE PAVEMENT MATERIALS

The problem statements in this subtrack will address environmental concerns in concrete pavement materials, construction, and performance. The materials developed in this research can be used to improve air quality and will enhance recycled concrete pavement materials. Table 61 provides an overview of this subtrack.

Problem Statement AM 3.1. 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 thus 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.

Tasks:

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.

Problem Statement AM 3.2. Sulfur Concrete

Sulfur concrete is made from sulfur collected from the petroleum refining process and coal ash from coal burning thermal power stations. The process applies vibration and pressure to a mixture of heated sulfur and coal ash. The resulting concrete is 100 percent recycled. Hardened sulfur concrete is dense and acidresistant enough to be used where PCC cannot be used. Although most concrete pavements will not need such a high level of resistance, a feasibility study may be warranted to determine whether sulfur concrete could be used for concrete paving.

Tasks:

1. Identify sulfur concrete mixes and their properties, including strength, permeability, and durability.
2. Evaluate the feasibility of sulfur concrete for concrete pavement, specifically constructability, durability, cost, and specific applications where it may be beneficial.
3. Develop recommendations for using sulfur concrete in concrete paving applications.

Problem Statement AM 3.3. 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 has 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.

Tasks:

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.

Problem Statement AM 3.4. 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; investigate its use in shorter performance life pavements, such as 8-year pavement; and investigate using portions of the product (i.e., fine or coarse fractions). FHWA’s program for recycled concrete should be reviewed before executing this effort.

Tasks:

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, 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.

Problem Statement AM 3.5. 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.

Tasks:

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.

Problem Statement AM 3.6. 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, also are 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.

Tasks:

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.

Problem Statement AM 3.7. Ecocement for Concrete Mixes

Ecocement replaces half of the traditional cement raw materials with ash generated by the incineration of municipal solid waste and sewage sludge. It has been recognized as type A energy efficient cement by the Japanese Institute of Civil Construction, Ministry of Construction, with the following characteristics:

• Rapid hardening, similar to high-early strength cement.
• Short initial setting time (approximately 20 to 40 minutes).
• Handling time that can be adjusted to suit particular applications by adding retarding admixtures.

During the Ecocement process, chinaware fragments in the incineration ash are used, and metal wastes are extracted and recycled. Research is needed to determine the viability of producing and using this material domestically in concrete pavements.

Tasks:

1. Identify the Ecocement material and its properties.
2. Identify the process for manufacturing Ecocement.
3. Determine the viability of producing Ecocement in the United States and the cost versus benefits of producing it.
4. Develop recommendations for producing and using Ecocement in concrete paving applications.

Problem Statement AM 3.8. Polymer Concrete Made from Recycled Plastic Bottles

Polymer concrete consists of organic polymers, typically unsaturated polyesters that bind inorganic aggregates that essentially replace the hydraulic binders in cement with organic polymers. Polymer concrete can be used alone or as an overlay or coating on ordinary PCC to increase its durability and lifetime dramatically. Recently, investigators have studied the use of resin obtained from recycled polyethylene terephthalate (PET) bottles (water and carbonated beverage containers). Recycled PET resin-based polymer concrete is stronger and cheaper than conventional polymer concrete. Recycling PET into polymer concrete also helps dispose of waste. Research is needed to determine the viability of this material for use in concrete pavements.

Tasks:

1. Identify polymer concretes made from recycled plastic and their properties—namely, strength, permeability, workability, durability, and cost.
2. Evaluate the viability and benefits of polymer concrete for concrete paving applications.
3. Develop recommendations for using polymer concrete for concrete paving applications, such as repairs, overlays, and new construction.