Improvements of Testing Procedures for Concrete Coefficient of Thermal Expansion

Abstract

The coefficient of thermal expansion (CTE) of concrete has a significant effect on the performance of portland cement concrete pavement. Concrete with a higher CTE is more prone to cracking, additional warping, and spalling. To improve PCC pavement performance, several districts of the Texas Department of Transportation (TxDOT) currently limit the CTE of concrete. To support this policy, efforts have been made to improve the accuracy and repeatability of the testing procedures for CTE. The current AASHTO Test Method TP 60 has been evaluated, its shortcomings identified, and improvements made. The improvements include CTE determination from regression analysis of temperature and displacement measurements. The effects of a number of variables on concrete CTE were investigated. The effect of the rate of heating and cooling is negligible. Concrete age and specimen size also have a negligible effect. Coarse aggregate content in the concrete mix has an effect on the test results. This test procedure was used to evaluate coarse aggregates from 32 sources in Texas. The results show that coarse aggregate type has a significant effect on concrete CTE. The proposed testing procedure for concrete CTE provided more accurate results than the AASHTO TP 60. TxDOT plans to implement this test procedure and to develop appropriate steel design standards for continuously reinforced concrete pavement and other construction-related requirements such as different curing methods for concrete with varying CTEs. This implementation should result in better concrete pavement performance.

Effect of materials and age on the coefficient of thermal expansion of concrete paving mixture

“…To prevent the temperature-related pavement deteriorations, several state agencies have made considerable efforts to determine the effects of the concrete mix design variables on the CTE so that the maximum CTEs can be limited to a certain value for the rigid pavement design (Won, 2005).…”

“…Several studies have conducted CTE measurements of concrete composed of locally available aggregate to examine the effects of the mix design parameter on the CTE (Jahangirnejad, Buch, & Kravchenko, 2009;Mallela et al, 2005;Tanesi, Kutay, Abbas, & Meininger, 2007;Won, 2005). Many researchers agree that the CTE value of concrete mixture is generally affected by coarse aggregate and sand types, volumetric proportion of the coarse aggregate and sand, and moisture condition.…”

“…To determine the effects of the concrete age on the CTE variation, Won (2005) examined the effects of the mix design variables, concrete age, and the heating and cooling rates on the CTE of concrete. Based on his study, it was concluded that the concrete age had little impact on the CTE for up to three weeks.…”

Effects of Aggregate Mineralogy on the Thermal Expansion Behavior of Concrete

“…Thermal expansion of concrete is generally influenced by aggregate type, aggregate volume proportion, curing age of the concrete, moisture condition, and water to cement ratio (Mallela et al, 2005;Tanesi 2007;Won 2005). The aggregate type significantly affects the CTE of concrete due to different thermal properties in aggregate that typically occupy 70 to 80 percent of the total concrete volume.…”

“…On the other hand, Jahangirnejad et al (2009) found the CTE value of concrete with gravel and igneous rock to be comparatively higher than concrete with sedimentary rock limestone. Won (2005) concluded that there is a linear relationship between the concrete CTE and the volume proportion of coarse aggregate. Although many studies have been made to identify the effects of coarse aggregate in concrete, the effect of fine aggregate on the CTE of concrete has not been well documented.…”