Effects of Concrete Age on Coefficient of Thermal Expansion of Paving Mixes and Its Significance in Unbonded Overlay Design

Abstract

Abstract With the advancement in rigid pavement design and advent of AASHTOWare Pavement Mechanistic-Empirical (ME) Design (American Association of State Highway and Transportation Officials, Washington, DC) as the latest design tool, increasing emphasis is being laid on the coefficient of thermal expansion (CTE) of concrete. The CTE affects the performance of rigid pavements in a significant manner, with a higher CTE corresponding to greater curling and resulting in greater pavement distresses. Prior research has conflicting views regarding CTE variation with age, and there has been very little to no research on the effects of CTE on the performance of unbonded concrete overlays (UBCOs). This study is performed to investigate the variation of CTE with concrete age through laboratory testing and further quantify the effects of CTE variation on UBCO design. To facilitate, four concrete paving mixes with different types of coarse aggregates and different mix properties from different districts of New Mexico were collected. The cast specimens from each of the mixes were tested for CTE as per the AASHTO T-336, Coefficient of Thermal Expansion of Hydraulic Cement Concrete, protocol, at the ages of 7, 14, 28, 60, 90, 120, and 180 days, respectively. The test results were analyzed, and it was observed that there is an increase in CTE over the range of 3.49 % to 9.77 %, between 28 days and 180 days. Further analysis was conducted with simulations in Pavement ME Design Version 2.3® that indicated a significantly deteriorated performance of the UBCO with increased CTE. The impact on transverse cracking and joint faulting is the most significant, with up to 13.3 % increase in cracking and up to 19.7 % increase in faulting distress. An unbonded overlay designed with 28 days CTE value may not perform for the design life because of the increase in CTE with age progression.