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Abstract
The Mechanistic-Empirical Pavement Design Guide (MEPDG) is a tool developed by NCHRP used to aid engineers in pavement design and performance analysis. MEPDG is currently incorporated into the software program AASHTOWare Pavement ME Design. The software uses statistical and mechanical models to predict pavement performance and degradation over time based on a number of inputs such as climate, traffic, and material properties. In order for the software to perform at the highest level of accuracy, AASHTO recommends a local calibration of inputs to be performed. The purpose of this research study was to provide additional material inputs for portland cement concrete (PCC) to the proposed catalog of inputs developed based on research performed as part of a previous NCDOT research project, RP 2015-03. To accomplish this, concrete mixtures containing varying amounts of fly ash and aggregates from sources different than those used in RP 2015-03 were batched and tested for mechanical properties, thermal properties, and durability performance. The influence of the aforementioned PCC materials and mixture proportions on the time-dependent change was also studied. Twenty-four concrete mixtures were produced using varying amounts of fly ash, four different coarse aggregate, and two different natural sands with proportions similar to what would be used in rigid pavement application across the state of North Carolina. Tests included compressive strength, modulus of elasticity (MOE), Poisson’s ratio, modulus of rupture (MOR), coefficient of thermal expansion (CTE), thermal conductivity, heat capacity, surface resistivity, and unrestrained shrinkage. It was determined that as expected, the amount of fly ash used in the PCC mixture had the most significant influence on the mechanical properties, thermal properties, and surface resistivity of the concrete. The coarse aggregate used in the mixture had a significant influence on all three thermal properties, CTE, heat capacity, and thermal conductivity. Time-dependent behavior of the PCC was also affected primarily by fly ash content. However, the coarse aggregate source did appear to be linked to some differences in time-dependent behavior observed in several tests, including compressive strength, modulus of elasticity, Poisson’s ratio, CTE, thermal conductivity, and heat capacity. Also notable was the finding that region of North Carolina from which the coarse aggregate was sourced also has an influence on the rate of change of surface resistivity. An expanded catalog of input values was prepared for NCDOT’s consideration for use in future pavement design.