Evaluation of Portland Cement Concrete coefficient of thermal expansion test protocol and the impact of CTE on performance of jointed concrete pavements.

摘要

A number of factors affect the magnitude of Portland Cement Concrete (PCC) coefficient of thermal expansion (CTE). The selected factors in this study were aggregate geology, age of the specimens, and the number of heating-cooling cycles applied to the test specimens. The effects of these variables on the measurement of CTE and the practical implications of the variables on the performance of jointed concrete pavements were investigated in this study.;A laboratory investigation was conducted to determine the CTE of typical concrete paving mixtures made with coarse aggregate from eight different sources in Michigan. The primary aggregate class included limestone, dolomite, slag, gravel, and trap rock. Three replicate test specimens were fabricated for each mixture-age combination. Over 700 specimens were fabricated to characterize the mechanical properties and CTE of the concrete specimens. The test specimens were moist-cured for 3, 7, 14, 28, 90, 180, and 365 days prior to testing. Mechanical properties tests including compressive strength, flexural strength, splitting tensile strength, and elastic modulus tests were conducted to check the quality and specification conformance of the concrete mixtures. The CTE was determined using two test methods; the provisional AASHTO TP60 protocol and a revised method based on the TP60 protocol. The measured average 28-day CTE values ranged from 4.51 to 5.92 muepsilon/°F (8.11 to 10.65 muepsilon/°C).;Statistical analyses were employed to evaluate the significance of the factors affecting CTE magnitude. These analyses included analysis of variance (ANOVA), which was performed using factorial treatment design and mixed effects models. The results of these analyses indicated that aggregate geology, specimen age at the time of testing, and the number of heating-cooling cycles that the specimen is subjected to, have a statistically significant impact on the magnitude of measured CTE.;Sensitivity analyses were conducted to investigate the practical impact of CTE and other variables on short-term (first 72-hours) and long-term performance of jointed concrete pavements using HIPERPAV II and M-E PDG software, respectively. The impact of PCC CTE among other pavement design variables (slab thickness, joint spacing, etc.) on pavement design and performance was investigated. The long-term impacts of the factors that were analyzed statistically are also discussed in this dissertation.;Recommendations are made to improve testing of the CTE based on the results of all analyses and suggested CTE values for agency use in Michigan were presented.