Measurement and Variability of Coefficient of Thermal Expansion for Concrete Pavements

The coefficient of thermal expansion (CTE) is an important parameter that affects the service life of concrete pavement. This document presents results of CTE measurements on concrete cores obtained from pavement sections in California. It describes details on the CTE measurement process followed at the University of California Pavement Research Center (UCPRC) along with variability associated with the testing method in terms of concrete soaking time and the effect of repeated thermal cycles. The testing method is based on AASHTO TP-60 (temporary protocol) with improvements suggested by researchers at the University of Texas Austin. Results of CTE measured by UCPRC were compared to results obtained from a small number of specimens previously tested at FHWA’s Turner–Fairbanks Highway Research Center laboratory and at the Concrete Materials laboratory at Texas DOT. It was observed that UCPRC results are in average slightly higher by about 0.09 microstrain/°F. Geographical variability of CTE was assessed comparing results from different regions within California. The overall range of CTE values obtained from 74 cores spans from 4.5 to 6.7 microstrain/°F. Specimens from four Caltrans Districts were compared and it was concluded that concretes in the coastal region have lower CTE compared to concretes in the north, south, and valley areas. CTE values from contiguous pavement sections of up to 6 mi, reveal a typical variability of approximately 0.5 microstrain/°F.