Mechanical behavior of concrete using seawater and sea-sand with recycled coarse aggregates

Adopting locally available seawater and sea-sand to produce concrete in marine and coastal projects is considered sustainable in concrete industry. This paper studies the mechanical behavior of seawater sea-sand concrete (SSC) and explores the feasibility of mixing SSC with recycled coarse aggregate (RCA). The early-age cracking and mechanical behaviors of SSC with or without the addition of RCA are experimentally studied. The results demonstrate that, compared with conventional concrete, the compressive strength of SSC with natural coarse aggregate (SSNAC) at 7 days increases by 36-76%, and the compressive strength at 28 days is similar while the compressive strength at 180 days decreases by 3.7-10.2%. The addition of seawater and sea-sand improves the mechanical behavior of recycled aggregate concrete, but deteriorates the early-age cracking behavior. Furthermore, the stress-strain relationship of SSNAC is analyzed, and applicability of the existing model is evaluated.