Papers by Keyword: Rebar Corrosion

Abstract: The chloride penetration depth and the corroded area on rebar were investigated for SHCC test specimens prepared with Portland cement on its own, and with 25% replacement with limestone powder. After being given bending cracks, the specimens were subjected to wetting and drying cycles of chloride solution by a ponding test. It was found that maximum chloride penetration depth was affected by the cover depth and the deformation applied to the test specimen. The corroded area on the rebar was correlated to the number of cracks in the SHCC and the total of the crack widths. For the same number of cracks and total width of the cracks, the corrosion area was greater in the mix with limestone powder.

Abstract: The applications of using fly ash-based geopolymer as a structural member and a repair materials in reinforced concrete structure was conducted. The optimum mix proportion of fly ash-based geopolymer concrete using for structural beam and fly ash-based geopolymer mortar using for repair material were developed. The flexural behavior of fly ash-based geopolymer reinforced concrete and the durability aspect namely the corrosion of steel reinforcement were investigated using the electrical acceleration. For the repair purpose, the fundamental properties; that is, compressive strength, flexural strength, bonding strength between fly ash-based geopolymer mortar and mortar substrate, setting time and chloride penetration were investigated. Also, the durability of conventional reinforced concrete beam repaired by the fly ash-based geopolymer mortar comparing with the comercial repair mortar was investigated. The behavior of the fly ash-based geopolymer reinforced concrete beam was similar to that of the conventional reinforced concrete beam; however, the corrosion of the steel reinforcement of the fly ash-based geopolymer reinforced concrete beam was higher than that of the conventional reinforced concrete beam. The fundamental properties of the fly ash-based geopolymer mortar were not different from that of the commercial repair materials; however, the durability of the reinforced concrete beam repaired by the fly ash-based geopolymer mortars performed a little lower than that of repaired with the commercial repair motar and also the control reinforced concrete with no repair. As a result, even there will be still a need of improvement there was a good tendency for using the fly ash-based geopolymer as the structural member and the repair materials.

Abstract: This paper presents the comparison of the two optimization methods, particle swarm optimization (PSO) and genetic algorithm (GA) in boundary element inverse analysis that applied to detect the corrosion location of rebar in the concrete. This comparison focuses at analyzing the performance of both methods in reaching the global optimum, considering that both heuristics are based on population search techniques. The model of 2-dimension rectangular reinforced concrete was used as a case example to compare both methods in boundary element inverse analysis. The boundary element inverse analysis was developed by combining Boundary Element Method (BEM) and PSO or GA. The inverse analysis is carried out by means of minimizing a cost function. The cost function is a residual between the calculated and measured potentials on the concrete surface. The calculated potentials are obtained by solving the Laplaces equation using BEM. The GA or PSO is used to minimize the cost function. Thus, the corrosion location of reinforcing steel in concrete can be detected. The numerical simulation results showed that one of PSO or GA can be used for the inverse analysis for detecting rebar corrosion by combining with BEM. However, it shows that PSO seem numerically superior compared to GA in term of consistency and accuracy in finding global optimum solution for such a problem.

Abstract: Particle Swarm Optimization (PSO) has been applied as optimization tool in various engineering problems. Inverse analysis is one of the potential application fields for PSO. In this research, the behavior of PSO, related to its inertia weight, in boundary element inverse analysis for detecting corrosion of rebar in concrete is studied. Boundary element inverse analysis was developed by combining BEM and PSO. The inverse analysis is carried out by means of minimizing a cost function. The cost function is a residual between the calculated and measured potentials on the concrete surface. The calculated potentials are obtained by solving the Laplace’s equation using BEM. PSO is used to minimize the cost function. Thus, the corrosion profile of concrete steel, such as location and size, can be detected. Variation in its inertia weight was applied to analyze the behavior of PSO for inverse analysis. The numerical simulation results show that PSO can be used for the inverse analysis for detecting rebar corrosion by combining with BEM. Also, it shows different behavior in minimizing cost function depending on inertia weight.

Abstract: In port engineering construction, the source of chloridion is concrete raw materials, admixtures and the penetration of seawater. Chloridion makes rebar corrosion, and makes the expansion and crack of reinforcement concrete, leading to concrete structural damage. By selecting the right concrete raw material, appropriate admixtures and to ensure concrete construction quality, in order to effectively avoid chloridion to the damage of reinforced concrete structures in construction.

Abstract: Based on the fundamental theory of electrochemical anodic polarization, simulated concrete is doped with corrosion inhibitor to prevent corrosion by chloride ion in the marine environment. Thus, with reference to the potential-time curves obtained in different concrete environments and construction conditions, the early dynamic state of active transition of rebar passive films in concretes can be quickly characterized. According to the experiments, the characteristics of passive active transition are synchronous with rebar corrosion. This helps to systematically study the influence of different components of concrete and external media on the durability of the concrete structure. The strong alkaline environment of the concrete is useful in controlling corrosion rate of reinforcing bar. As one of the additional protective measures of the durability of the concrete structure, corrosion inhibitor’s long-term performance contains uncertainty.

Abstract: Due to the volume expansion of corroded rebar products, the cracking of the concrete cover would occur, and has a serious impact on the durability of the concrete structure. In this paper, a numerical model was established for the simulation of the corrosion of rebar in concrete structures with the aid of finite element analysis software. The distribution of stress in concrete around rebar, that due to the expansion of these corroded rebar products, was obtained. The theory of elasticity method is used to validate the distribution of stress in concrete around rebar. The location of cracks would be predicted by the distribution of stress in concrete around the rebar.