Valorization of recycled materials in development of self-compacting concrete: Mixing recycled concrete aggregates – Windshield waste glass aggregates

Abstract

Abstract The presented paper is based on a comparative experimental study aimed to incorporate coarse recycled concrete aggregates (RCA) and coarse recycled glass aggregates (RGA) from waste glass “windshield” in the composition of self-compacting concrete (SCC). The main objective is to study the influence of these aggregates on fresh and hardened concrete properties. In order to reach this purpose, two series of SCC mixes were prepared by replacing natural coarse aggregates (NCA) by RCA and RCA by RGA. The key properties of SCC recommended by European specifications and guidelines (EFNARC), were measured in the fresh state. While the compressive strength, water absorption testing and the observations on cross-section to evaluate the stability and segregation potential, were conducted on hardened concretes. For replacement of NCA by RCA, the use in SCC fine and coarse recycled concrete aggregates is not advisable, the flowability criteria cannot be ensured. The experimental results showed that the slump flow test has given a diameter of 610 mm. Likewise, also the L-box blocking ratio was limited to 0.2. The replacement of RCA by RGA did not significantly affect the initial slump, the obtained values are all above the minimum threshold of 650 mm. EFNARC criterion of passing ability is also satisfied. The yield stress and the plastic viscosity, determined by empirical equations, are in agreement with those observed with traditional SCC. The compressive strength of the RGA–SCC mixes decreased with an increase in recycled glass content but remain within the strength range of self-compacting concretes. The results have showed that it is possible to produce SCC with windshield waste glass aggregates.