Computer-Based Guidelines for Concrete Pavements Volume I-Project Summary

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CHAPTER 1. INTRODUCTION

This report describes the efforts undertaken to enhance the Federal Highway Administration (FHWA) High Performance Concrete Paving (HIPERPAV®) computerized design and construction guidelines by incorporating jointed concrete pavement (JCP) long-term performance prediction models, continuously reinforced concrete pavement (CRCP) early-age behavior models, and two additional modules with results from related FHWA studies.

1.1 Background

When the first generation of the software, HIPERPAV I, was first developed in 1996, a new approach was born: a total systems approach to concrete paving. In this simple to use, yet technically complex piece of software, the power to simulate problems before they happen is now a reality. In the past few years, FHWA has sponsored the expansion of this concept into a usable and reliable tool. Contractors, suppliers, agencies, and academics all can utilize the power in this approach.

The total systems approach has now proven itself with the end-user. This project continued this development by incorporating additional modules in a new software generation, termed HIPERPAV II. For example, a CRCP module has been added. CRCP has been used by a number of States as a durable concrete paving alternative. Although more expensive initially, many CRCP sections have given excellent performance with little to no maintenance.

Long-term pavement performance (LTPP) is also now being considered in HIPERPAV II. As a result of the work done under the Strategic Highway Research Program (SHRP), an extensive database has been compiled that contains a wealth of valuable data related to design, construction, and performance of hundreds of pavements throughout North America currently available to the pavement community. A number of additional models have been developed since that time.

In 1996, as part of the LTPP program, a critical gap was identified to predict properly the performance of concrete pavements: the early-age conditions. "Early-age" in this case is the period of performance (typically 48-96 hours) that is critical in establishing the benchmark for future pavement performance. In this project, the early-age mechanisms that influence long-term performance have been investigated. Experienced practitioners have always recognized this cause and effect, and now the total systems approach to concrete paving is the vehicle to tie these mechanisms together.

In recent years, FHWA has sponsored a number of projects related to various aspects of concrete paving. The end results of these studies are valuable assets. These assets, however, must be shaped into a form that the end-user can readily accept. Findings from two of these FHWA studies were incorporated into the total systems approach vis-à-vis HIPERPAV II. As a result, two new modules were integrated; a dowel analysis module and a concrete mix optimization module.

1.2 Project Objectives

There are three objectives for the work conducted in this project:

1. Develop a module capable of predicting the impact on long-term jointed plain concrete pavement (JPCP) performance as a function of early-age behavior.
2. Develop a module capable of predicting the early-age behavior of CRCP.
3. Develop additional modules that incorporate results from existing FHWA studies related to concrete paving.

Table 1 graphically depicts these additions to the HIPERPAV II software. HIPERPAV I is characterized by cell 1 in this table. Project objectives 1 and 2 have been accomplished by developing the modules shown in cells 2 and 3, respectively. An additional module that might be developed in the future would meet the attributes of cell 4. This additional module could characterize the long-term performance of CRCP as a function of early-age behavior.

Table 1. Proposed additions to the HIPERPAV II software.

1.3 Project Scope

The scope of this study is to assemble these key elements into a user-friendly, practical, and reliable end product using a total systems approach. In this document, this approach is described and its benefits are demonstrated. This unique approach allows the project objectives to be accomplished and helps ease the integration of new features in the future. The total systems approach allows the various components of the current HIPERPAV I to be integrated easily to work in conjunction with the proposed modules to be developed in HIPERPAV II. Figure 1 demonstrates the interaction of the various modules within the overall HIPERPAV II system. The baseline element of this approach is the core of the HIPERPAV system. The core predicts the temperature transport as well as key portland cement concrete (PCC) behavior such as curling, warping, and shrinkage. The various shaded modules orbiting about the core are modules that make up the HIPERPAV II system. In some cases, modules are interrelated. For example, the Early-Age JPCP module (from HIPERPAV I) drives the Long-Term Performance module for JPCP developed in this effort.

The user interface also has been modified to accommodate the additional modules and to add the flexibility for the addition of future modules.

The system is analogous to a puzzle; however, instead of beginning to assemble the pieces from the outside toward the center, the opposite is true here. Each piece is a module, and the final look of the puzzle will continue to change as the pieces continue to be added. Continuing this analogy, for the puzzle to be assembled, each of the pieces must be shaped correctly for an exact fit. This describes the work conducted for this project.

BCO = bonded concrete overlays

Figure 1. Schematic of total systems approach to the HIPERPAV II system.

1.4 Report Structure

This report describes the work conducted to enhance the HIPERPAV concrete pavement design and construction guidelines. ^[1] The remaining chapters of this report are organized as follows:

Chapter 2: Previous HIPERPAV Feedback and Provisions for Future Implementation

Chapter 2 presents a description of implementation efforts of the computer guidelines. Comments from current users of the guidelines and desired enhancements are listed and prioritized. This chapter also documents the creation of the technical expert panel (TEP) for HIPERPAV II. The guidance and direction received from the TEP members throughout the development of the enhanced guidelines is summarized.

Chapter 3: Information Search and Model Selection

This chapter documents the identification of the models that were incorporated in the guidelines. This includes the literature review conducted for identification and selection of updated theoretical models on JPCP early-age pavement behavior, JPCP long-term performance models, and CRCP early-age behavior models. In addition, this chapter describes the efforts to identify and incorporate two additional FHWA studies related to the design and construction guidelines. A detailed description of each individual model incorporated is reported in volume III of this report series. Also presented in that volume is a detailed annotated bibliography on the primary references reviewed during the information search performed in this study.

Chapter 4: Guidelines Enhancements and Evaluation

This chapter describes the approach taken for development of the final HIPERPAV II software product, including a description of the functionality of the JPCP long-term performance, CRCP early-age behavior, and additional FHWA modules. The design of the user interface, and development approach for incorporation of each of the individual modules into the total analysis tool, is also described.

In addition, this chapter briefly describes the approach for validation of the software guidelines. A detailed description of the validation efforts is reported in volume III of this report series.

Chapter 5: Summary, Conclusions, and Recommendations

A brief summary of the steps taken throughout the project for enhancing and evaluating the guidelines is presented in chapter 5. Major findings identified throughout development of the guidelines are summarized in this chapter. In addition, recommendations for future enhancement of the guidelines with additional modules and features, as well as incorporation of more sophisticated models, are outlined.