Experimental study of self-leveling mortars produced with recycled concrete aggregates

This study evaluates the use of recycled concrete aggregate (RCA) in self-leveling mortars (SLM) to obtain certain rheological characteristics for use in screed concrete. Mixtures were produced with 50% and 75% of RCA in substitution of natural fine aggregate (NFA) by varying the type of additive (polyfunctional plasticizer and combination of superplasticizer and viscosity modifier). In order to achieve a better distribution of water amid the grains in the residue, the RCA was pre-wetted by spraying for 10 min before mixing. The properties evaluated were: specific mass in the fresh stage, tensile strength, spreading, flow retention, regeneration time, and exudation rate. Regarding the variation of the type of chemical additive, all the mixtures had valid rheological aspects. The exudation rate values were less than 3% and the minimum curing time was 15 min. Also, all mortars achieved values above 2 MPa in the flexural strength tests, which was the minimum expected according to the literature. The use of RCA can be considered, and through the proper adjustments of chemical additives it can provide formulations with adequate rheological characteristics without losses on their mechanical properties.