This paper summarizes work performed under the Strategic Highway Research Program project R21 on developing MEPDG-compatible mechanistic-empirical design procedures, test methods, and construction guidelines and specifications, for two-lift PCC/PCC composite pavements and HMA/PCC composite pavements. Composite pavements consisting of high quality top layer(s) have been proven in Europe and in the United States to provide long lives with excellent surface characteristics and rapid renewal when needed. The lower PCC layer is a sustainable JPC or CRC pavement that utilizes recycled and lower cost locally available materials, thus reducing the need to haul aggregates over long distances. As part of this research, three full-scale instrumented test sections on the MnROAD mainline roadway (I-94, west of Minneapolis) were constructed in Spring 2010. The sections include one HMA/JPC and two two-lift PCC sections subject to real highway traffic. Accelerated Pavement Tests (APT) using the Heavy Vehicle Simulator (HVS) were used at the University of California Pavement Research Center (UCPRC) at Davis to evaluate various HMA/PCC test sections. These test sections were constructed in Fall 2009. The research also includes evaluation of in-service composite pavement across the U.S., Canada, and Europe. The results from these experiments were used to develop performance models and procedures for designing HMA/PCC and PCC/PCC composite pavements.

MIT Scan technology is a non-destructive method to measure the alignment of dowel bars placed in transverse joints of jointed plain concrete pavements (JPCP). Misalignment of dowel bars can potentially lead to reduced load transfer efficiency (LTE), cracking, spalling and faulting. Several agencies across the U.S. have adopted specifications for dowel bar misalignment, many using the joint score methodology. However, this methodology has never been validated using field studies. National Cooperative Highway Research Program (NCHRP) Report 637 provides a methodology to determine an effective dowel diameter; however, this was based on laboratory testing and limited field studies. This paper presents results of a Federal Highway Administration (FHWA) project to collect MIT Scan data on Long Term Pavement Performance (LTPP) sections. The analysis did not indicate any definitive relationship between joint score and cracking/spalling within the analysis range for most States. This is not to say that severely misaligned dowel bars do not affect pavement performance, particularly localized distresses. Analysis of effective dowel diameter as a measure of dowel misalignment for use with Pavement ME suggests that using effective dowel diameter is a less biased estimator of long-term LTE as modeled using Pavement ME than using actual dowel diameter, thus suggesting a relationship between dowel misalignment and long-term LTE. The remaining bias and scatter suggests that models (effective dowel diameter model and LTE model in Pavement ME) can be improved using the data collected as part of this study.

As a part of the Highways for LIFE initiative, the Federal Highway Administration provided a $1.2 million grant to the Nevada Department of Transportation (NDOT) to rehabilitate the highway structures on I-80 Elko County. This project involved (1) Rehabilitation of Carlin Tunnels, (2) Reconstruction of pavement structures, (3) Rehabilitation of eight bridge structures, and (4) Operational improvements to highways and tunnels. The key innovation employed on this project was the construction manager at risk (CMAR) method of construction delivery, which was expected to extend the service life of the highway structures while significantly reducing the duration of construction. Another important element of this project was to completely renovate the lighting system within the Carlin Tunnels using new light-emitting diode (LED) luminaires. In fact, this is the first project in North America that used an LED lighting system for highway tunnels. The overall objective of this project was to improve the structural condition of I-80 through Carlin Canyon and provide operational and safety improvements, which was accomplished innovatively through this project.

Composite pavements have proved in Europe and the United States to have long service life with excellent surface characteristics, structural capacity, and rapid renewal when needed. This project developed the guidance needed to design and construct new composite pavement systems. Volume 1 presents the state of the practice and guidelines for designing and constructing new hot-mix asphalt (HMA) concrete over a portland cement concrete (PCC) composite pavement that takes full advantage of using differing materials. Volume 2 provides guidance on the design and construction of two-layer, wet-on-wet PCC pavements where the upper layer is a thin high-quality layer (hard nonpolishing aggregate, higher cement content, higher quality binder) and excellent surface characteristics with the lower layer containing a higher percentage of local aggregates and recycled materials. Both volumes detail performance data on existing composite pavement systems and provide step-by-step guidance on the design of composite pavements using mechanistic-empirical design methods for both types of new composite pavements.

Recent efforts under the Strategic Highways Research Program (SHRP2) project R21, “Composite Pavements,” lead to the design and construction of composite portland cement concrete (PCC) pavement sections at the Minnesota Road Research Facility. This construction is part of a larger effort to further understand techniques that lead to an infrastructure that is both rapidly renewed and sustainable. This paper will discuss successes and challenges of composite, or two-layer, PCC pavements, based on first-hand experience at MnROAD and on the SHRP2 R21 scanning tour of European composite pavements. This article represents a follow-up to an earlier article in Transportation Research Record No. 2098 on the R21 scanning tour of European composite pavements and observations of European construction practices for composite paving.

Composite pavements consisting of a relatively thin functional top layer of high quality asphalt or concrete bonded to a lower layer of concrete materials have been utilized in Europe and to a limited extent in the United States. These composite pavements have generally provided long structural lives through design aimed at exceptionally low concrete fatigue damage but also with good surface characteristics (smoothness, low noise, and high friction). The surface layer can consist of a variety of asphalt bound materials including hot-mixed asphalt (HMA), stone matrix asphalt (SMA), or rubber-asphalt porous friction courses. The surface characteristics of the top layer can be rapidly renewed as needed with no structural repairs required to the lower layer. The lower layer is typically a sustainable yet structurally sound portland cement concrete (PCC) layer that utilizes recycled and/or lower cost locally available materials, thus reducing the need to haul aggregates and pavement materials over long distances. This paper describes the design and construction of a sustainable composite pavement test section constructed as part of the Strategic Highway Research Program 2 (SHRP 2) project R21. The instrumented 150 mm (6 in) PCC jointed pavement with a 75 mm (3 in) hot-mix asphalt (HMA) riding surface was constructed in Spring 2010 on Interstate 94 at the Minnesota Road Research Facility (MnROAD) in Albertville, just northwest of Minneapolis. Successes and challenges of constructing new HMA/PCC composite pavements using recycled materials based on first-hand experience are presented. Agencies with existing old deteriorated concrete or asphalt overlaid pavements may find that the recycling of these pavements directly into a lower low cost recycled concrete aggregate (RCA) slab surfaced with a high-quality asphaltic surface (HMA, SMA, rubber-asphalt porous friction course) could be an economical alternative. Results also are applicable to widening an existing old HMA/PCC type of pavement.

Contractors constantly have to make decisions about maximizing profits while considering risks associated with choosing construction target levels for various acceptance quality characteristics (AQCs). With more and more states adopting incentive–disincentive pay adjustment provisions for quality as measured by various AQCs, a contractor likely has to evaluate several options before selecting an optimum target quality that will maximize profit at an acceptable level of risk. The greater the number of AQCs, the more complex the assessment that the contractor is required to perform and the less intuition and experience can be relied on. The updated Probabilistic Optimization for Profit (Prob. O. Prof. 2.0) is a computer program used as a probabilistic-based tool designed to assist portland cement concrete and hot-mix asphalt paving contractors in evaluating statistical quality assurance specifications. In addition, it assists the highway agencies in evaluating the appropriateness of their specifications and ensuring that they have no undesirable consequences. This procedure allows the agency to adjust pay factors accordingly while developing specifications. The Prob. O. Prof. 2.0 program is discussed, and examples of its use are provided.

The California Department of Transportation (Caltrans) recently completed a study to evaluate the performance of edge drain systems placed along portland cement concrete (PCC) pavements. To date, a variety of edge drain designs, backfill materials, and placement methods have been used and have resulted in varying degrees of success when measured against overall pavement performance. This study investigated several different types of edge drain systems that have been used by Caltrans. Their performance was evaluated, and it was observed that more than 70 percent of the surveyed edge drains were not performing efficiently or as designed. This poor overall result can be attributed to design flaws, improper construction practices, and lack of maintenance. Generally, the performance of originally constructed edge drains was better than retrofit projects, since originally constructed edge drains are generally equipped with larger diameter drain pipes, deeper trenches, and treated permeable bases. Edge drain trenches in retrofit projects are generally not deep enough to effectively collect all infiltrated water from the PCC and base layers. The geotextile filter fabric materials found in excavated projects are not soil-specific, which can cause clogging and eventually reduce the ability of these edge drains to allow free flow of water. Improper construction practices, such as high percentages of cement in cement-treated permeable base backfill material and improper placement of geo-fabric material were observed in a few of the surveyed edge drain projects. Among surveyed projects, more than 50 percent of the edge drain outlet pipes were either buried or clogged, which can be attributed to lack of maintenance.

The California Department of Transportation (Caltrans) recently completed a study to evaluate the performance of edge drain systems placed along portland cement concrete (PCC) pavements. To date, a variety of edge drain designs, backfill materials, and placement methods have been used and have resulted in varying degrees of success when measured against overall pavement performance. This study investigated several different types of edge drain systems that have been used by Caltrans. Their performance was evaluated, and it was observed that more than 70 percent of the surveyed edge drains were not performing efficiently or as designed. This poor overall result can be attributed to design flaws, improper construction practices, and lack of maintenance. Generally, the performance of originally constructed edge drains was better than retrofit projects, since originally constructed edge drains are generally equipped with larger diameter drain pipes, deeper trenches, and treated permeable bases. Edge drain trenches in retrofit projects are generally not deep enough to effectively collect all infiltrated water from the PCC and base layers. The geotextile filter fabric materials found in excavated projects are not soil-specific, which can cause clogging and eventually reduce the ability of these edge drains to allow free flow of water. Improper construction practices, such as high percentages of cement in cement-treated permeable base backfill material and improper placement of geo-fabric material were observed in a few of the surveyed edge drain projects. Among surveyed projects, more than 50 percent of the edge drain outlet pipes were either buried or clogged, which can be attributed to lack of maintenance.

Although dowel bars are an essential design feature of jointed concrete pavements to prevent pumping and faulting, few studies dealing with the constructability of dowel alignment have been conducted. With the emergence of the Magnetic Imaging Tools (MIT) Scan-2 as a nondestructive, robust method of locating dowels, it is now possible to efficiently evaluate the construction quality of dowel bar placement without damaging the newly constructed pavement. A brief review is presented of the results of recent field studies aimed at examining the constructability of doweled joints in concrete pavements. The dowel bar alignment data collected in this study encompass a wide range of design and environmental conditions and show that alignment within reasonable levels—considering equipment, mix design, as well as workmanship and consistency—is achievable in the field. Distress and performance analyses show that within these levels of misalignment, the pavement performance is not significantly affected. However, misalignment at a greater level may not be detrimental to pavement performance, and therefore performance-based guidelines may be less strict than the constructability levels collected in this study. Nevertheless, the results shed light on the level of alignment that can be reasonably achieved in the field.

The primary objective of this study was to develop, implement, and evaluate a Level 1 performance-related specification (PRS) for the construction of a jointed plain concrete (JPC) pavement in the State of Wisconsin. The research entailed a thorough evaluation of the construction quality levels achieved on recent Wisconsin JPC projects and the formulation of a Level 1 PRS using the results of the quality evaluation and defined Wisconsin Department of Transportation (WisDOT) pavement practices as a basis. The Level 1 PRS defined the sampling and testing requirements for four acceptance quality characteristics (AQCs)―thickness, strength, air content, and smoothness―and the corresponding performance-based pay factor curves for each AQC. The Level 1 PRS was included as an overriding special provision in the December 2005 letting of a JPC paving project located on I-39/90/94 near Madison, Wisconsin. Implementation of the PRS took place March through June 2006, corresponding to the mainline and tied-shoulder paving performed in both directions on this project. AQC measurements obtained from the I-39/90/94 project were used to compute PRS pay factors and establish pay adjustments for the contractor. High smoothness and strength levels achieved by the contractor coupled with more generous incentives for smoothness as compared to existing WisDOT specifications, resulted in significant incentives for the contractor under the PRS. Feedback from WisDOT and the contractor indicated that this first PRS implementation in Wisconsin was successful, particularly with respect to the layouts of lots and sublots. Several suggestions were received to improve and streamline the PRS process.

With increasing damage due to the combination of increasing traffic load applications, adverse climate, and increasing frequency of trench cutting and patching associated with utility work, residential streets are requiring more frequent, extensive, and costly maintenance and rehabilitation (M&R) to maintain adequate levels of serviceability during pavement design life. Increased cost of M&R and eventual reconstruction are an added burden on already limited city budgets. To rectify this situation, city managers and engineers are looking at enhancing current structural design standards for residential streets to increase their load-carrying capacity. With an increase in load-carrying capacity, it is hoped that frequency of M&R will be reduced and the design life of such pavements will be extended. However, adopting a higher design standard has significant cost implications. The question then becomes, Will the expected increase in initial cost be offset by the significant decrease in M&R costs and corresponding increase in pavement life that will delay. eventual reconstruction? The Minnesota Department of Transportation (DOT), on behalf of the Local Road Research Board, initiated a study to evaluate the impact of enhancing residential street pavement design standards to accommodate greater axle loads on life-cycle costs. The primary focus was to compare the life-cycle costs of residential streets designed using Minnesota DOT's 5- to 7-ton and 9- to 10-ton design standards. The study concluded that life-cycle cost for the 5- to 7-ton and 9- to 10-ton design standards was not significantly different at the 95% significance level.

Instrumented concrete slabs were constructed in Palmdale, Calif., in order to fail the slab sections under accelerated pavement testing. Prior to fatigue failure testing, these slabs were monitored over 24 h cycles without load, and under a slow-moving 40 kN rolling wheel load. Slab temperature profiles, edge and corner deflections, and interior vertical deflections were collected at 2 h intervals. A finite element program was used to analyze the deflection data and calculate an effective built-in temperature difference (EBITD) through the slab, which represented the combined effects of nonlinear "built-in" temperature gradients, irreversibie shrinkage, and creep. Differences in restraints (from adjacent slabs, shoulder, and base friction) and variability in material and structural properties resulted in wide variation in the measured EBITD. High EBITD values (-20 to - 35 degrees C) were observed for sections with low restraint. and low to moderate EBITD values (0 to -20 degrees C) observed for sections with higher restraint.

Differential expansion and contraction between the top and bottom of a concrete slab results in curling. Curling affects slab stresses and deflections and is an important component of any mechanistic-empirical design procedure for concrete pavements. Although some curling is caused by temperature and moisture gradients that fluctuate daily, a significant portion of the curling can be attributed to the combined effects of nonlinear “built-in” temperature gradients, irreversible shrinkage, and creep, which can be represented by an effective built-in temperature difference (EBITD). A procedure for estimating EBITD of in situ slabs using a falling-weight deflectometer and a finite-element program is presented. This procedure was used to estimate EBITD for instrumented slabs at Palmdale and Ukiah, California. Differences in restraints (from adjacent slabs, shoulder, base friction) and variability in concrete material properties resulted in EBITDs ranging from -5°C to greater than -30°C.