Degradation under cyclic wet-dry aging of full-scale high-workability concrete maximizing sustainable raw materials

Abstract

Analyzing and validating the behavior of sustainable concrete mixes under near-realistic conditions is essential to advance their use. In this research, full-scale high-workability concretes, 0.5 m3 in volume, containing maximum amounts of sustainable raw materials and their response in cyclic wet-dry tests are studied. The mixtures contained Electric Arc Furnace Slag (EAFS) and Recycled Concrete Aggregate (RCA) as aggregates, and Ladle Furnace Slag (LFS) and Ground Granulated Blast-furnace Slag (GGBS) as binders. Each mixture underwent 30 wet-dry cycles with temperature variations between 20 °C and 70 °C. Throughout the cycles, the internal-damage level was assessed through (increasing) weight measurements, (decreasing) ultrasonic-pulse-velocity readings, thermal strain, hardened-property variations, and flexural deformability. Overall, all the mixes underwent initial internal damage, attributable to both the thermal shock that increased with each cycle and the aging of the cementitious matrix, which in turn resulted in shrinking that reduced their thermal deformability. A linear thermal expansion coefficient of 1.6·10-5 °C-1 was adequate for safely estimating all the maximum thermal strains. Internal damage was less relevant with the use of EAFS and GGBS that led to fewer strength decreases, which were only 15–20% compared to 25–30% in the RCA mixes. However, the combination of EAFS and LFS increased flexural deformability after the test, which resulted in compliance under bending stresses that was two times higher than in the other mixes. Under those conditions, the joint use of EAFS and GGBS was the most recommendable multi-criteria and multi-purpose option where any change in concrete composition significantly affected behavior.