Feng Mu

Comparison of measured vs. predicted performance of jointed plain concrete pavements using the Mechanistic–Empirical Pavement Design Guideline

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°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.

An evaluation of the built-in temperature difference input parameter in the jointed plain concrete pavement cracking model of the Mechanistic-Empirical Pavement Design Guide

This paper evaluates the implementation of the built-in temperature difference input parameter in the Mechanistic–Empirical Pavement Design Guide (MEPDG) for the design of jointed plain concrete pavements (JPCPs). The pavement distress, in terms of transverse cracking, is expected to be minimised when the transient temperature difference is equal in magnitude to the built-in temperature difference but of the opposite sign. However, this study shows that a built-in temperature difference of − 6.5°C minimises the cracking prediction for JPCPs. This optimum value of − 6.5°C coincides with the default value in the MEPDG of − 5.5°C, which was established through the nationwide calibration. The cause of this phenomenon is further investigated by taking into account the traffic loading time, slab thickness, joint spacing and reversible shrinkage, but none of these factors are able to explain this anomaly. The results from this study indicate that the built-in gradient should not be an input but is merely a calibration constant. A comparison between predictions using the measured and default built-in temperature difference again supports that it is better characterised as a calibration constant.

Establishing Effective Linear Temperature Gradients for Ultrathin Bonded Concrete Overlays on Asphalt Pavements

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.

An evaluation of JPCP faulting and transverse cracking models of the mechanistic-empirical pavement design guide

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.

Comparison of response for three different composite pavement sections to environmental loads

Abstract 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.