Self-compacting concrete with recycled concrete aggregate subjected to alternating-sign temperature variations: Thermal strain and damage

Any variation in temperature alters the dimensions of a concrete structure and provokes thermal stress. Moreover, the propagation of micro-cracking decreases the strength of concrete that is exposed to sub-zero temperatures (freezing), to heat phenomena (heating), or to cyclical thermal variations, especially when prepared using Recycled Concrete Aggregate (RCA). A reference self-compacting concrete (SCC) mix made with 100% coarse and fine natural aggregate and three SCC mixes containing 100% coarse and/or fine RCA in replacement of natural aggregate were tested in this study of the thermal performance of SCC and the related effects of RCA. The mixtures were subjected to five thermal tests designed with positive and negative, and both constant and cyclical, extreme-ambient temperature variations, reaching temperatures of − 15 °C and 70 °C. Stiffness, weight, compressive strength, thermal deformability, and internal damage of the SCC mixtures were monitored throughout suitable testing. Internal damage, hygroscopicity, and loss of strength increased at temperatures below 0 °C, especially in the mixtures containing 100% coarse RCA, although the SCC manufactured with simultaneous additions of fine and coarse RCA fractions showed the worst performance. Overall, RCA performed better under positive temperature variations. The test results lead to the recommendation of a linear thermal expansion coefficient of 1.2·10−5 °C−1 in calculations for SCC containing RCA under those extreme environmental conditions.