Thermal conductivity and its effects on the performance of PCC pavements in MEPDG

Abstract

This study developed a standard thermal conductivity test procedure to test concrete specimens and studied factors influencing those specimens. The thermal conductivity of concrete is significantly affected by moisture content, type, and percentage of coarse aggregate; this finding was confirmed statistically by Analysis of Variance (ANOVA). The study also developed a model for predicting the thermal conductivity of concrete that varies with moisture content and the coarse aggregate percentage. To understand the effect of supplementary cementitious materials (SCMs), this study also measured thermal conductivity of control and ternary mixtures. An increase in thermal conductivity percentage due to increase in moisture was higher in ternary mixtures, compared to normal concrete mixture. Thermal conductivity of ternary mixtures fluctuated with change in their unit weights. An Enhanced Integrated Climatic Model (EICM) model was required to analyze the effects of the thermal conductivity of concrete on temperature and the moisture profile of pavements. An EICM model analysis showed that temperature in the middle layer of concrete pavement decreased as thermal conductivity increased, and temperatures remained constant for higher thermal conductivity values. A change in thermal conductivity had no effect on top and bottom pavement temperatures. Temperature profiles were measured in a concrete block to compare the EICM predicted temperature profile in plain cement concrete (PCC) pavements. Temperatures inside the concrete block embedded in soil at several depths were higher, compared to temperatures predicted by the EICM model. The measured temperatures attain a peak hour temperature gradient on the hottest time of the day, but the EICM model did not predict the peak hour temperature gradient. Our research performed Mechanistic Empirical Pavement Design Guide (MEPDG) analysis to estimate the effect of thermal conductivity on distresses such as cracking, faulting, and the international roughness index (IRI). We found that thermal cracking increased with decrease of thermal conductivity. We also found that an Integrated Climatic Model (ICM) stability failure occurred for a set of thermal conductivity and heat capacity readings in MEPDG analysis. Finally, this research found a strong correlation for the thermal conductivity and heat capacity values that resulting in ICM stability failure.