A comprehensive evaluation of the effects of climate in MEPDG predictions and of MEPDG EICM model using MnROAD data

University of Minnesota M.S. thesis. March 2011. Major: Civil Engineering. Advisor: Lev Khazanovich. 1 computer file (PDF); viii, 75 pages.Although new construction of composite (AC/PCC or PCC/PCC) pavements is not common, a substantial amount of knowledge has been acquired over the past 35 years regarding the materials, design, and construction of composite pavements. The Mechanistic-Empirical Pavement Design Guide (MEPDG) provides useful prediction models, analysis methodologies, and a design procedure that, with further improvements and calibrations, can be made to provide reasonable prediction capabilities for new composite pavements. This thesis investigates the applicability of the MEPDG models for predicting structural responses of composite pavements, with special attention paid to the geographic location of the pavement section, and the temperature distributions predicted by the EICM for a composite pavement. A section of this thesis examines the effects of climate on pavement performance, and the effect of climate file generation using the MEPDG. This section details the effort to design and test an asphalt-over-concrete (AC/PCC) composite pavement for 610 locations across the United States using the MEPDG version 1.0. While results support the general notion of environmental effects on pavement performance, the performance prediction was found to contain inconsistencies in terms of predicted transverse cracking in the PCC layer. These inconsistencies are attributed to climatic data, and they include the use of stations with incomplete data. It was concluded that the climatic database available to the MEPDG should be cleansed of incomplete or questionable climatic data files to ensure accurate transverse cracking prediction in AC/PCC. Otherwise, the presence of this questionable climatic data can only adversely affect performance prediction. The other primary focus of this thesis describes research aimed to evaluate modeling of the thermal behavior of concrete and composite pavements by the Enhanced Integrated Climatic Model (EICM), the climate modeling package used in the MEPDG. The study uses temperature data collected at the Minnesota Road Research facility from PCC and iv AC/PCC pavements to first investigate benefits of AC overlays on the thermal characteristics of PCC slabs. Furthermore, the study validates EICM predictions of thermal gradients through the slabs and investigates the effect of MEPDG user inputs for thermal conductivity of the PCC. This section examines measured data from MnROAD for AC/PCC pavements and their single-layer PCC counterparts and attempts to explain how similar pavement systems and their thermal characteristics are accounted for in the MEPDG. The research concluded that evaluation of the material thermal inputs should be a part of a process of local calibration and adaptation of the MEPDG. Also included in this paper is a sensitivity analysis to a wide range of input parameters that might be expected for composite pavements. This includes AC and PCC layer thickness, PCC joint spacing, PCC slab width, and the coefficient of thermal expansion in the PCC layer. Thermal properties of the materials that can affect the temperature distribution, thermal conductivity and heat capacity, are also included in the sensitivity analysis. This thesis concludes that the environmental and material thermal property inputs should be considered with equal importance as traffic, design features, and non-thermal material properties