Rust expansion cracking behaviour of new Cr alloy-reinforced coral aggregate concrete

Abstract

The rust expansion cracking behaviour of Cr alloy-reinforced coral aggregate concrete (CAC) was studied by theoretic and experimental methods to analyse the serviceability limit state of concrete. The corrosion product composition of the Cr alloy rebar was analysed to determine the stability and protection of the rust layer. The critical corrosion ratio model of Cr alloy-reinforced concrete was established by considering the influence of water–binder ratio, admixtures and fibres, relative protective layer thickness, Cr alloy reinforcement type and reinforcement placement. The results demonstrated that owing to the loose and porous characteristics of CAC, the corrosion products filled the concrete, resulting in critical corrosion ratio of the rebar being much larger than that of ordinary concrete (OC). When Cr alloy was added to a carbon rebar, the rust layer structure and corrosion products of Cr alloy rebars changed significantly, thereby improving the stability and protection of the rust layer. The protection coefficients of HPB300, Cr1, CrAl, Cr3, Cr5, and Cr8 rebars were 0.211, 0.286, 0.304, 0.490, 0.670, and 0.964, respectively. The rust layer density of the Cr alloy rebar was high, hindering the erosion of the harmful medium in concrete. The critical corrosion ratios of Cr1, CrAl, Cr3, Cr5, and Cr8 reinforcements increased by 0.72%, 1.81%, 4.01%, 11.60%, and 29.35%, respectively. When Cr (5%–8%) was added to the rebar, the corrosion time of reinforcement began to rust and concrete cracking was prolonged. This was beneficial for preventing concrete cracking caused by rebar corrosion.