Coated reinforcements are expected to improve the performance of reinforced concrete in aggressive environments, but different kinds of coated reinforcements can express a variety of properties, which can confuse researchers and engineers. This paper reviews the manufacture, corrosion mechanisms, behaviors, and applications of popular or promising coated reinforcements, incorporating galvanized reinforcements (GRs), epoxy coated reinforcements (ECRs), stainless cladding reinforcements (SCRs), and steel-fiber reinforced polymer composite bars (SFCBs). In terms of manufacture, GRs and ECRs should focus on minimizing the negative effect of manufacture on performance, while SCRs and SFCBs should reduce the cost and increase the production capacity. Behaviors of GRs and ECRs are primarily determined by the steel substrate, but the behaviors of SCRs and SFCBs are primarily affected by the coat and core, and their interaction. The corrosion mechanism of GRs and SCRs is about oxidation, while that of SFCBs is about hydrolysis. ECRs are usually corroded under film, which can be a cause of premature failure. Corrosion embrittles SCRs, as well as bare bars, but corrosion of SFCBs usually causes a reduction in maximum strength. The investigation of the corrosion behaviors of GRs and ECRs focuses on bond strength. GRs have controversial performance. ECRs have been proven to have drawbacks regarding bond strength. The use of anti-corrosion reinforcement is uneven in regions, which may correlate with the development of technology and the economy.
Bimetallic steel bar (BSB) consisting of S30408 stainless steel (cladding layer) and HRB400 carbon steel bar (substrate) has outstanding durability, indicating its suitability for RC structures in corrosive environments. The effects of fire on the mechanical properties of BSB in relation to its metallographic structure (MS) were investigated experimentally by exposing BSB specimens to different elevated temperatures and cooling methods. When the exposure temperature (ET) was lower than the austenite transformation temperature, the changes in the MS were relatively small. When the ET was higher than 700°C, lamellar pearlite and lath martensite were formed in the substrate of BSB specimens with cooling in air (CIA) and cooling in water (CIW), respectively, which led to changes in the mechanical properties. The hardness of the BSB specimens also was affected by the ET and cooling method. There always was a yield plateau in the stress–strain curve of the BSB specimens with CIA. When the ET ranged from 700°C to 900°C, the formation of granular pearlite improved the homogeneity of cementite in ferrite, which enhanced the ductility. For BSB specimens with CIW, when the ETs were 800°C and 900°C, the yield plateau in the stress–strain curve disappeared because of the lath martensite in the substrate. Ductile dimples were observed in the scanning electron microscope images of the BSB specimens with CIA. However, for BSB specimens exposed to 900°C with CIW, the ductile dimples were almost negligible.
5 August 2023 in Construction and Building Materials