PMM has been widely used because of its high durability performance though it is relatively expensive. Unfortunately, many early re-deteriorated cases have been observed just a short time after the first repair. The re-deterioration is due to the fact that important factors like deteriorated grasp, time, material of repair, environmental influence etc., are not considered carefully for the repair work. Among those factors, the environmental impact has been hardly examined up to now. Therefore, the purpose of this research was to quantitatively evaluate the environmental impact on the performance of patching repair material. In the experiment, the material and mix design of PMM were varied widely. The environmental conditions were : Seal, Dry and Windy, Low-temp and High-temp conditions. Evaluation techniques were elucidation of cement hydration and film process of polymer in PMM. This study examined the influence of above factors on strength and durability of PMM. And, the stiffening model of PMM was constructed based on quantitative experimental results.
Two types of concrete specimens containing chloride were prepared to suffer early frost damage. A freezing and thawing test was performed on the specimens, which were then subjected to the electrodeposition technique in an external solution containing deicing salt (sodium or calcium chloride). Electrodeposits appeared to fill the fine cracks caused by frost damage because the relative dynamic modulus of elasticity of concrete specimens was considerably restored after electrodeposition in the calcium chloride solution. The electrodeposition technique was also capable of improving the durability factor of the frost-damaged specimens. However, when the electrodeposition technique was carried out in the sodium chloride solution, the frost-damaged concrete specimens suffered more frost damage.
The quality and quantity of the residual mortar greatly influence the quality of the recycled coarse aggregate and change with the mix proportion of the original concrete. In this study, an experimental examination was performed focusing on the water binder ratio and the fine aggregate content of the original concrete that influence the quality of recycled coarse aggregate and recycled aggregate concrete. As a result, it was found that the quality of the recycled coarse aggregate containing the residual mortar of the original concrete is almost equal to that of the original aggregate when the water binder ratio and the fine aggregate content of the original concrete are low.
The mechanical properties of reinforcing bar is known to affect the ultimate state of reinforced concrete structures. This study investigates how chloride-induced corrosion of rebar affects its elongation characteristics. With a view to establishing a practical assessment method for residual performance of existing RC structures, this study has employed a method of estimating the strength and elongation characteristics of rebar using only a vernier caliper. The results of this study can be summarized as follows; Residual sectional area of corroded rebar can be estimated by measuring the residual diameter of rebar. Elongation capacity reduces to 20percent with the residual area of rebar being in a range of 70 to 80percent. The stress-strain relationship and failure strain of corroded rebar can be estimated based on the stress-strain relationship of sound rebar and the smallest sectional area of corroded rebar.
This research attempted to grasp flexural capacity of RC (Reinforced Concrete) beams connected with loop-shaped re-bar joints through experiments of one-way bending and alternating bending. As the experimental results, it became clear that the RC beams connected with the loop-shaped re-bar joints have enough abilities in both flexural capacity and energy absorption, if compared with the RC beams having usual lap splice joints or continued re-bars. In addition, the effects of arrangements of loop-shaped re-bars, reinforcements inside the loops, and so on are discussed in this paper.
The Nondestructive evaluation technique by thermography is increasingly being used as a tool for the maintenance of the concrete structures. In most applications, the evaluation of only the location and shape of defects on planes is expected, therefore, no method has been developed for evaluating the depth of defects. This paper describes a method that evaluates the three-dimensional shape of delaminations. After heating the target area, thermographies are taken sequentially. Then, temperature curves obtained at each pixel during convected cooling are analyzed by the Fourier series expansion. By Fourier analysis, it is shown that the phase delay of the temperature curve contains information on the depth of defect. In addition, the phase differences between the areas with and without defects have peak values at a specific period of processing the data. This specific period is related to the depth of the defects. Delaminations are introduced into the concrete specimen by applying expansion pressure from an inserted tube. It is found that the three-dimensional shape of the delaminations can be evaluated by the proposed technique.
This paper presents an analytical study to evaluate the residual structural performance of RC members damaged due to steel corrosion. A lattice model is focused on and developed to evaluate the shear resisting mechanism of corroded RC beams. An interface element is modeled for the bond behavior between corroded reinforcement and concrete and incorporated into the lattice model. The analysis shows that the shear carrying capacity of the RC beams having sufficient anchorage reinforcement increases when the bond between the longitudinal reinforcement and concrete degrades as the steel corrosion proceeds. This behavior of the RC beams can be explained by means of the response of arch elements in the lattice model that represent the formation of the tied arch mechanism in the beam.