The US spends an estimated $91 billion on US highways every year, with most pavement expenditures going to maintenance of the existing system. However, congestion is a major issue. It is estimated that congestion leads to 5.5 billion wasted hours and 2.9 billion gallons of wasted gas, costing $121 billion annually. Expansion of the system is needed, but current funding streams are not even able to keep up with maintenance needs. The primary approach to address this challenge has been to increase funding. While this is needed, agencies also need to improve the efficiency of their roadway investments to get more out of their pavements. This can be accomplished in two ways. First, agencies can increase competition in the pavement bidding process. Basic economics confirms that when there is competition among many contractors and across paving industries, the average unit prices for pavements are lowered significantly. The second way is to improve the management of the pavement assets to increase the average life of the network. A longer life network, though it may initially cost more, has a larger return to both the agency and the driving public in reduced expenditures and congestion. This paper will show how agencies can improve the pavement network investment efficiency using these two items.

Concrete pavements are often constructed by first paving the mainline followed by the shoulder some time later. It is important to factor the differences in the structure, material properties, and climatic conditions between the mainline and the shoulder into design and construction; otherwise, premature cracking can develop. This study uses finite element modeling to analyze the causes of the transverse cracking in the newly paved shoulder of U.S. Route 22 near Blairsville, Pennsylvania. The key factor responsible for the cracking is identified as the construction sequence causing thermal incompatibility between the mainline and the shoulder. A parametric study is then carried out to quantify the significance of many factors, such as construction sequence, material properties, pavement features and environmental conditions, on the cracking potential. A guideline is then established to prevent the future occurrence of the cracking.

A previous sensitivity study indicated a tendency of Pavement ME to predict more transverse cracking for Jointed Plain Concrete Pavements (JPCP) with aggregate bases than those with stabilized bases. Such a tendency contradicts the experience of some engineers who have successfully used aggregate bases to achieve robust and enduring JPCPs. The controversy triggered an in-depth investigation of the JPCP models by comparing them to an independent 3-D finite element model, which showed that Pavement ME under predicted the environmental stress for JPCPs with stabilized bases and also neglected the benefit of aggregate bases in accommodating the deformation of the surface layer and thus reducing its stress. However, this investigation was solely based on numerical modeling and not validated by any field evidences. This study further examines the issue based on an analysis of SPS-2 JPCP field experiments of the long-term pavement performance (LTPP) database. While the SPS-2 sections were designed to investigate the effect of various factors such as base type, thickness, climate, and so forth on the structural performance of the JPCP, this study is focused on the comparison of different base types, namely dense graded aggregate base (DGAB), permeable asphalt treated base (PATB) and lean concrete base (LCB). The interplay between base type and the other factors is also discussed.

The debonding mechanism of bonded concrete overlay of asphalt (BCOA) due to fatigue loading was investigated quantitatively based on an accelerated loading test. During the test, a nondestructive technique was deployed to measure the area of interface debonding. In addition, a numerical model incorporating a cohesive-zone based interface was developed to calculate the fracture energy associated with the interface debonding. Finally, the fatigue algorithm of the interface debonding was established by relating the area of debonding to the fracture energy. This fatigue algorithm can be used to predict the degree of BCOA debonding due to repeated traffic loading and the consequent stress increase in the overlay. Its development is of great significance, because it not only represents the physics of BCOA debonding more closely than the other existing models, but can also greatly improve the accuracy of the predicted life of the BCOA when incorporated into the design process.

For the design of new jointed plain concrete pavements (JPCPs), three national calibrations of the AASHTOWare Pavement ME have been necessary due to updates in either the prediction models or the calibration database. Local calibration is recommended to further refine predictions so that they better match a state’s experience. To date, local calibration efforts resulted in eight states changing one or more coefficients to a local value, while eleven states have decided to directly adopt national calibration coefficients. To determine the impact of local calibrations relative to the national calibration, a review of the national and local calibration efforts was completed. Local and national calibration coefficients were compared in two scenarios. In the first scenario, Pavement ME was employed to evaluate the performance of a hypothetical JPCP section. In the second scenario, Pavement ME was used as a tool for determining the thickness of pavements with various design features. It was found that for most states the pavement performance differed quite significantly between the local and national calibrations. However, in terms of design thickness, no evident difference could be statistically concluded for most of the states. In comparing designs developed using AASHTO 1993 Guide for Design of Pavement Structures, it was found that the Pavement ME yielded thinner designs regardless of the calibration coefficients used.

Composite pavement structures are constructed mainly either as Portland cement concrete (PCC)-over-PCC or hot mix asphalt (HMA)-over-PCC. Several successful in-service projects have been reported in Europe. The design and construction of these sections in the United States, however, still require effort. The current study includes the analysis of the response of three different composite pavement sections to the environmental loads. These sections were constructed in May of 2010 at the Minnesota Road Research Facility. The sections are constructed in three individual cells, Cell 70, a HMA-over-PCC with recycled concrete aggregate (RCA), Cell 71, exposed aggregate concrete (EAC)-over-RCA and Cell 72, EAC-over-economical concrete. All cells were heavily instrumented with thermocouples, moisture sensors, and static and dynamic strain gauges. This study characterises the structural response of HMA-over-PCC pavements and also PCC-over-PCC to the environmental loads.

A cohesive zone model is proposed to simulate the interface debonding, a preponderant cause of failure for bonded concrete overlay of asphalt (BCOA). The model is constructed by superimposing four root models, each representing the mechanism of one subcritical failure at the interface zone observed in laboratory experiments. The model parameters are established through an inverse analysis of wedge splitting tests performed on BCOA specimens. These inputs are mainly a function of the materials at the interface zone, such as microtexture and macrotexture, and thus can be expected to be applicable to the numerical simulation of a full scale BCOA slab. For modeling across scales, the impact of specimen size, milling depth and initial flaw size on the model, in terms of peak traction and fracture energy, is also discussed.

This study evaluates the modeling of different base types under new jointed plain concrete pavements (JPCP) in the AASHTO Pavement ME Design Guide. It was found that the Pavement ME overestimated the stress in JPCP for unbonded stabilized bases and granular bases and underestimated the stress for bonded stabilized bases when compared to other models. The error in stress estimation results from modeling an unbonded base with a bonded-but-weightless base in the structural model, which is critical when the environmental loading is predominant and/or the base is stiff. Because the separation between layers that are not bonded cannot be accommodated, the behavior of a granular base cannot be accurately reflected, especially not by an elastic continuum.

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Bonded concrete overlay of asphalt (BCOA) is a viable technique for rehabilitating distressed asphalt pavements by bounding a Portland cement concrete overlay to the asphalt pavement. BCOAs are more durable solutions especially for highways and major city intersections where the constant maintenance using bituminous materials is not desirable. They also have advantages over the unbonded concrete overlays in terms of lower cost and lesser concern of the overhead clearance. As a result, BCOA has gained increasing popularity over the past two decades. Up to 2010, over 300 projects have been recorded in more than 35 states, totaling over 7.5 million m2. The key to a successful BCOA is to maintain the concrete-asphalt bond. When the bond is effective, the neutral axis of the overlay is shifted lower resulting in smaller tensile stress in the concrete and thereby allowing the thin overlay to carry large amounts of traffic. However, the bond degrades due to fatigue and the loss of the bond results in premature failure of the BCOA. Because of the lack of understanding to the interface debonding mechanism, the current BCOA design procedures still employ constant adjustment factors developed based on limited projects to account for the increase in the overlay stress due to partial bonding. The use of such empirical constants might lead to very unreliable design. Therefore, a quantitative framework that can predict the growth of interface debonding as a function of the fatigue loading could be a key to improving the current design procedures. A fracture mechanics based framework has been developed to determine the growth of debonding area as a function of the number of fatigue loads and the fracture energy subjected by each individual load. Wedge splitting tests were first performed to understand the interface fracture and investigate the debonding resistance of the interface under Mode I loading. Accelerated loading tests were then conducted on BCOA slabs to simulate the fatigue of the interface bond. In addition, a transient-wave based nondestructive method was developed to detect the growth of the interface debonding and a cohesive zone model was established to calculate the fracture energy.

This research evaluates the reasonableness of the Mechanistic-Empirical Pavement Design Guide (MEPDG) version 1.0 to predict the joint faulting and transverse cracking of jointed plain concrete pavements (JPCPs). This is accomplished by carrying out a full factorial sensitivity analysis, considering material properties, pavement design features, climates and traffic. This study considers the interaction and correlation between these inputs and was designed to reflect the real conditions that occur in practice. Based on over 3000 runs, the sensitive parameters in the joint faulting model and the transverse cracking model were identified. In general, the analysis indicates JPCP models perform well. However, some counterintuitive results were also found.

The effective linear temperature gradient is a significant input needed to characterize the effects of environmental loadings when available pavement design procedures are used for bonded concrete overlays on asphalt (BCOA), also known as thin or ultrathin whitetopping. Establishing such an input is challenging and therefore has not been well guided in current BCOA design procedures across the country. Guidance is provided on suitable values for the effective equivalent linear temperature gradient (EELTG) that can be used in the design of ultrathin BCOAs. The EELTG is expressed as a function of the climatic conditions, geographical location, and design features of the BCOA: longitude, latitude, elevation, annual mean percentage of sunshine, overlay panel size, 28-day modulus of rupture for the portland cement concrete, and thickness of the hot-mix asphalt layer. Typical values for the annual mean percentage of sunshine are recommended to facilitate implementation of the proposed guideline in the current design procedures.

Six sections of jointed plain concrete pavements (JPCPs) throughout the state were selected as candidates for the evaluation of premature deterioration. The data used in performing the evaluation included manual and historic automated distress survey data, falling weight deflectometer data, and laboratory material characterization data from field samples. For these six sections, a variety of issues including material-related distress, fatigue, and construction deficiencies were determined to be the cause of the premature deterioration. Recommendations for rehabilitating these sections as well as guidelines to deter the reoccurrence of these distresses have been provided.

An approximate analytic relationship is developed between the maximum radial stress on the shaft of a displacement pile in sand and the base resistance of the pile. Using the cavity expansion analogy, together with a confined failure mechanism, the ratio between the two quantities, defined as a factor St, is established as a function of the friction angle, shear stiffness, compressibility and mean effective stress of the sand near the pile tip. It is shown that, given otherwise identical input parameters, the value of St will decrease with increasing friction angle, and with decreasing mean stress level. It also tends to decrease with an increase in relative density. It is predicted that St has typical values between 0·03 and 0·05, in broad agreement with the range of empirically derived values in the literature. The relationship also predicts that St may take much higher values (∼0·1) for piles installed in dense sand or in highly compressible sand. Because of the analytical nature, the established relationship provides useful insights into the mechanisms involved and important implications for design practice.

This research evaluates the ability of the Mechanistic-Empirical Pavement Design Guide (MEPDG) to accurately predict the performance of jointed plain concrete pavements (JPCPs). This is accomplished by comparing predicted performances with observed performances for the in-service mainline test cells at Mn/ROAD. These comparisons indicate that MEPDG performance predictions for JPCP are most accurate when the default (constant) built-in equivalent temperature difference of -5.5 degrees C is used instead of a site-dependent value. It appears that significant portions of the error of estimation can be explained by the sensitivity of the performance models to variability in hardened concrete properties (modulus of rupture, modulus of elasticity and coefficient of thermal expansion) and pavement structural features (slab thickness, joint spacing, subbase type and bond condition). Predictions of slab cracking were found to be highly sensitive to these parameters. In addition, the MEPDG cracking model seemed not to fit local cracking observations for the Minnesota test cells. New calibration factors are needed to more accurately predict Minnesota JPCP slab cracking. This study also included comparisons of predicted service lives for the Mn/ROAD test cells using different design methodologies and as-built input parameters. In most cases considered, the MEPDG predicted longer service lives than did the 1993 AASHTO procedure. The MEDPG also predicted longer service lives than the PCA procedure for the 5-year cells but shorter service lives for the 10-year cells. This infers that, when holding service life constant, the MEPDG generally results in thinner concrete pavement sections than the 1993 AASHTO procedure.