Recycled aggregate concrete using seawater: Optimizing concrete's sustainability

Abstract

Concrete is the most widely used building material worldwide and causes huge carbon emissions, high water consumption and negative impacts on the environment. In this context, in order to reduce natural resources consumption and obtaining a “greener” concrete, the use of seawater and recycled aggregates becomes a promising option. In this study, the effect of the use of seawater in the composition and curing of concrete with natural aggregates (NA) and recycled aggregates (RA) applied at different ratios (0 %, 50 % and 100 %) on its mechanical and durability properties was evaluated. By applying structural equation modelling (SEM) with the R version 4.2.2, the dependence relationships between the variables were empirically evaluated. The analysis of the results has made it possible to establish the advantages and disadvantages of the manufacture of concrete with seawater and RA. It was found there is a need to increase the water/cement ratio in concrete made with seawater, the effective water/cement ratio was increased by 0.03 with respect to the control (in order to maintain workability constant) and that the use of seawater did not influence the mechanical properties of concrete made with NA. However, in concrete made with RA, the mechanical properties improved with the presence of seawater in the mixing, 39 MPa compressive strength at 28 days was obtained for concrete made with 50 % of RA. Durability properties were negatively affected by the presence of seawater and RA, with an increase in water absorption, shrinkage and carbonation depth. The seawater curing process did not influence the mechanical and durability properties of concrete. These results indicate that seawater alone does not influence the mechanical and durability properties of concrete. However, there the combined effect of seawater and RA improves the final characteristics of concrete.