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Publication Number: FHWA-04-122
Date: February 2005

Computer-Based Guidelines for Concrete Pavements Volume II

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CHAPTER 1. INTRODUCTION

The HIPERPAV® II system was developed as a tool for predicting the early-age behavior of both Jointed Plain Concrete Pavements (JPCP) and Continuously Reinforced Concrete Pavements (CRCP). In addition, the effect of early-age behavior factors on JPCP long-term performance has been addressed. It is expected that the above predictive capabilities will help designers, contractors, and concrete suppliers identify factors that can contribute to achieving good performing pavements. Similarly, it is expected that factors that could potentially put the pavement's long-term performance at risk also can be identified.

It is important to recognize the numerous factors affecting the performance of a concrete pavement, and furthermore, when and how these factors come into play during the various stages of a pavement project. For example, planners may use HIPERPAV II to develop quality control specifications for projects based on the available materials and climatic conditions in the region of construction. For designers, HIPERPAV II may be used to optimize pavement designs so that an improved long-term pavement performance is achieved. For contractors, HIPERPAV II may be used to prevent expensive pavement repairs. Higher potentials of cracking due to unexpected changes in the weather can be predicted and avoided. Using HIPERPAV II, the impact of these changes on the pavement is quantified, and an alternative construction time or method can be developed to reduce or altogether prevent pavement damage. Suppliers may use HIPERPAV II to assess the performance of a given mix design under various climatic conditions. Finally, HIPERPAV II may be used as a forensic analysis tool for pavements. For example, engineers can better pinpoint the reasons behind pavement damage and/or poor pavement performance.

With these considerations in mind, this document aims to provide theoretical concepts on early-age behavior and long-term pavement performance, providing a basis for understanding the numerous models in HIPERPAV II. Ultimately, understanding the above concepts will help guideline users select from the wide range of design and construction alternatives available. Finally, a user's guide for the HIPERPAV II system is presented at the end of this document.

1.1 BACKGROUND

The original HIPERPAV I system provided design and construction guidelines for JPCP. This set of guidelines provided recommendations for selecting primary inputs that influence the early-age behavior of JPCP.(1) In this document, the guidelines are extended to cover the design and construction of CRCP. In addition, the JPCP guidelines are extended to consider the inputs of various early-age parameters on long-term performance.

If well designed and constructed, CRCP is one of the best alternatives for heavily trafficked roads. This is especially true when minimizing user delays due to maintenance, providing long-lasting smoothness, and minimizing user costs are important considerations. Identifying factors that influence the early-age behavior of CRCP will therefore provide the basis for developing adequate guidelines to improve current design and construction practices.

Several investigations have addressed the importance of early-age behavior on long-term performance of concrete pavements.1,2,3) Most of the factors that influence the early-age behavior of concrete pavements can be classified into four different categories: pavement design, materials and mix design, environmental, and construction operations. Based on these factors, initial conditions have been identified that are known to influence the performance of the pavement in the long term. Such initial conditions or early-age indicators of long-term performance include joint/crack opening, built-in curling, and surface delamination due to moisture loss. This document identifies the primary early-age indicators influencing the long-term performance of the pavement. To understand their progression with time, the effects of traffic and long-term environmental factors are also discussed.

1.2 OBJECTIVES

The primary objective of this volume is to serve as a stand-alone document covering a comprehensive set of guidelines useful in the design and construction of both JPCP and CRCP concrete pavements. Good design and construction practices not only will help prevent immediate (early-age) problems from occurring, but also may improve performance in the long term. To accomplish this, this document will cover guidelines on the following topics:

1. Early-age behavior of JPCP and CRCP pavements.

2. Early-age distresses that may result from poor design or construction practices.

3. Early-age indicators that can influence long-term pavement performance (e.g., joint opening, crack spacing).

4. Long-term pavement distresses that relate to early-age factors (e.g., cracking, punchouts, faulting).

In addition, this document also provides sample case studies that illustrate the proper use of HIPERPAV II to optimize concrete pavement behavior and contains a user's manual.

1.3 SCOPE AND FORMAT

Chapter 2 presents a brief description of early-age concrete pavement behavior. "Early age" in these guidelines is defined as the first 72 hours after pavement construction for both JPCP and CRCP. According to experience, the potential for damage to the pavement structure due to excessive thermal and moisture related stresses is significant during this time. However, in the case of CRCP, the cracking behavior continues to change until approximately 1 year after construction. After 1 year, cracking commonly remains constant. HIPERPAV II predicts the cracking behavior of CRCP during the early age and also during the early life (up to 1 year) to realistically assess the behavior of CRCP inservice. Primary early-age indicators influencing long-term pavement performance for JPCP and CRCP are also discussed in this section.

In chapter 3, early-age concrete pavement distresses such as plastic shrinkage cracking and thermal shock are discussed. Considerations are made for both JPCP and CRCP.

Chapter 4 presents a mechanistic approach to the impact of early-age behavior on long-term performance. The influence of early-age indicators on each individual distress type will be discussed. Primary distress types associated with early-age pavement behavior addressed include faulting, spalling, transverse cracking, corner cracking, spalling, and punchouts.

Chapter 5 provides recommendations and guidelines for inputs selected from five unique categories: pavement design, materials and mix design, environment, construction, and traffic inputs.

Sample case studies are presented in chapter 6, with design and construction scenarios to illustrate the proper use of the guidelines. The guidelines have been developed with two possible scenarios in consideration: a proactive scenario, and a post-mortem scenario.

The proactive scenario is one that may occur anytime during the planning, design, or construction stages of a project. Under this scenario, the guidelines user may refer directly to chapter 5—HIPERPAV II Input Parameters—for the proper selection of HIPERPAV II inputs under the five categories of pavement design, materials and mix design, environment, construction, and traffic. Because these guidelines provide only general guidance with the selection of the input parameters in these categories, it is the user's responsibility to use engineering judgment in the final selection of the inputs.

For the case of the post-mortem scenario, the guidelines user may be experiencing a particular problem either occurring in the early age or during the long term. For this particular case, the user may refer to chapter 3, Early-Age Pavement Distresses, or chapter 4, Impact of Early-Age Behavior on Long-Term Performance, according to the nature and timeframe of the specific problem.

Under both scenarios, the user may refer to chapter 2, Early-Age Pavement Behavior, for a detailed understanding of the mechanisms occurring during the early age that influence the performance of the pavement in the long term.

Finally, chapter 7 is a user's guide for the HIPERPAV II system.

 

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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.
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