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.
In marine engineering, using corals as aggregates to prepare concrete can reduce both the exploitation of stones and the transportation cost of building materials. However, coral aggregates have low strength and high porosity, which may affect the workability and mechanical properties of concrete. Hence, superfine cement is used innovatively in this study to modify coral aggregates; additionally, the effects of the water–cement ratio and curing time on the water absorption and strength of modified coral aggregates are investigated. Modified coral aggregate concrete is prepared, and the effect of using modified superfine cement on its workability and strength is investigated. Experimental results show that when the water-cement ratio exceeds 1.25, the slurry does not form a shell on the surface of the coral aggregates and the water absorption of the coral aggregates increases significantly. The strength of the modified coral aggregates cured for a short duration is slightly lower than that of unmodified coral aggregates, whereas that cured for 28 days is approximately 20% higher than that of unmodified coral aggregates. Using superfine cement to modify coral aggregate concrete can improve its workability, but not its compressive properties.
Corrosion is an unavoidable problem for RC structures in harsh marine environment, which encourages the application of high‐performance concrete (HPC) and corrosion‐resistant reinforcements, such as stainless steel (SS), stainless‐clad bimetallic steel (SB) and FRP. Especially, for the RC structures in remote islands or reefs, the use of local materials (coral, sea water, etc.) may bring cost benefits by avoiding the high expansive fee. In this paper, the cost effectiveness of five different material proposals is evaluated and compared based on the life‐cycle‐cost analysis (LCCA), incorporating not only initial cost but also long‐term investment into account. The LCCA results of a 3‐floor office building in the South China Sea shows that basically the SB + HPC proposal shows the highest cost benefits considering a 100‐year period while the proposals using coral aggregate seawater concrete (CASC) are not that competitive. The sensitivity analysis is performed to address the influence of discount rate and construction‐to‐material cost ratio.
31 October 2022 in Journal of Rock Mechanics and Geotechnical Engineering
High-strength steel (HSS) is widely used in engineering structures, due to its superior material performance, but corrosion tends to occur in steel structures with time. The corrosion effects on mechanical performance of Q620 HSS were investigated experimentally. The electrochemical accelerated corrosion test was conducted to generate corroded Q620 HSS specimens (ρ = 0~60%). With increases in the corrosion degree, corrosion performance became more and more non-uniform. The tensile coupon test was conducted to clarify mechanical properties of corroded Q620 HSS specimens. With increases in corrosion degree, fy, fu, εu and E decreased, correspondingly. The effect of corrosion on εy could be ignored. With the deepening of corrosion, the necking of Q620 HSS specimens was weakened, which reduced their ductility. The simplified constitutive model consisting of nominal yield point (εy, fy) and ultimate point (εu, fu) was proposed to quantify the mechanical properties of Q620 HSS with different corrosion degrees. After the numerical fitting, relationships between the corrosion degree and mechanical properties were clarified. Based on the results of numerical fitting, mechanical properties of corroded Q620 HSS specimens were worse than those of specimens with idealized uniform corrosion. The adverse effect of corrosion on εuc was more obvious than that on strength properties. Comparison among different mild steels and HSSs was performed. Different indexes were chosen to clarify corrosion effects on the ductility of corroded Q620 HSS specimens. This study considers and discusses the research on corrosion rates, the relationships between service time, service environment, corrosion form and strength properties of Q620 HSS.
1 December 2021 in Journal of Building Engineering