Scaled concrete beams containing maximum levels of coarse recycled aggregate: Structural verifications for precast-concrete building applications

Abstract

The use of Recycled aggregate (RA) enhances concrete sustainability. If used on an industrial-scale, structural verification, and testing will be required to confirm that RA concrete can meet relevant industrial standards and the requirements of manufacturers, especially in the precast-concrete industry. In this paper, an experimental campaign with the participation of a precastconcrete manufacturer is reported. The objective is to test a self-compacting concrete (SCC) mix, designed for structural applications, that contains maximum amounts of 100% coarse RA, in order to establish its compliance with the habitual requirements of precast-concrete manufacturers. Thus, scaled beams (12 24 180 and 24 24 130 cm) were subjected to bending, shear-bending, shear, and long-term-deflection tests. In addition, the performance of that SCC mix in the bending and shear-bending tests was compared with the performance of an SCC mix of similar compressive strength containing 0% coarse RA. In the failure tests, the experimental results were between 1.5 and 3 times higher than the required values. The elastic behavior of both SCC mixes was also very similar in those tests, regardless of the amount of coarse RA, due to the robust design of the water and superplasticizer content of the SCC, which balanced the decreased flowability and the lower compressive strength of SCC that resulted from the additions of coarse RA. The SCC mix with 100% RA showed a lower load-bearing capacity after failure and narrow compliance margins with the deflection limits of the long-term-deflection test. Even though the SCC mix with 100% RA met all the standard technical specifications of the precast-concrete manufacturer, reference should always be made to the serviceability limit states that are applicable at the time of the structural design phase