This paper discusses the effect of the compressive and tensile strength of inorganic polymer concrete (IPC), protection layer thickness and bonded length of reinforcing bars (rebars) on the bond performance between IPC and rebars through laboratory tests of IPC at high temperatures. In addition, the bond performances of IPC and ordinary concrete at high temperatures are compared. The experimental results indicate that IPC at high temperatures exhibits superior bond performance with rebar compared with ordinary concrete. As the temperature increases, the reduction in the IPC-rebar bond strength exhibits similar behavior as the reduction in the compressive and tensile strengths of IPC. Thin protection layers contribute to significant degradation of the IPC-rebar bond strength at high temperatures. The degradation of the bond strength is affected by the rebar bonded length at room temperature but is not influenced at high temperatures. The analytical expression of the IPC-rebar bond strength at high temperatures can be derived by best fitting the experimental results. Based on the expression of the ultimate bond strength and the expression of rebar slip, a two-segment regression analysis is performed to obtain the local bond-slip relationship of rebars in IPC after exposure to high temperatures. This study provides theoretical contributions to the engineering application of IPC.
Realkalisation and desalination are electrochemical repair methods for reinforced concrete structures damaged by carbonation and chloride attack respectively. After completing realkalisation and desalination, surface protection method could be applied for sustaining the repair effect of electrochemical repair methods for a long time. However, past papers reported that the surface coating materials are sometimes deteriorated at an early stage due to the highly alkaline atmosphere of concrete after the application of the electrochemical repair method.
In this research, the performance of surface treatment materials applied to the concrete after realkalisation or desalina-tion was investigated. Furthermore, the protection effect of the surface treatment against steel corrosion after realka-lisation and desalination under the condition of accelerated carbonation or chloride attack was estimated by measuring electrochemical steel corrosion indexes. As a result, the bond strength of polymer-cement mortar (PCM) or epoxy resin on concrete applied realkalisation maintained the sound level through the accelerated carbonation for 2 years. Moreo-ver, the re-passivation of the steel in concrete after desalination occurred more quickly in the cases of silane-based im-pregnation than in the cases of PCM or epoxy resin.
This study conducts an experimental program to calibrate a proposed arch resistance model that can be used to evalu-ate the residual axial load-carrying capacities of shear-damaged reinforced concrete (RC) columns. An extreme dam-age pattern of shear-damaged RC columns in which the axial load is carried by the longitudinal bars only due to spalling of the concrete core is considered in the experimental program. To simulate this extreme damage pattern, five bare specimens with different clear lengths are fabricated using only steel bars and tested to axial collapse under different axial loads. Based on the experimental results, the force-displacement behavior, limit state of the axial collapse, and stress state of the longitudinal bars of the shear-damaged RC columns are investigated for the proposed arch resistance model. The ratios of the analytical to the measured residual axial capacities in the designed specimens are between 0.77 and 0.92, demonstrating the high accuracy of the proposed model. In addition, the effects of post-yield strain hardening of the longitudinal bars on the force-displacement behavior and on the accuracy of the residual axial capacities of the shear-damaged RC columns are discussed.
In this study, the development of carbonation resistance in blast furnace slag (BFS) mortar when using silicone oil (SO) is investigated. Moreover, the influence of SO on drying shrinkage and frost resistance are investigated. The results indicate that SO tends to improve the carbonation resistance of BFS blended mortar and reduces drying shrinkage; however, it decreases frost resistance. The water repellency of SO has a positive effect on carbonation and drying shrinkage. Furthermore, there is a possibility that SO prevents the consumption of calcium hydroxide (CH) by carbonation and hydration in portland blast furnace slag cement type B (BB) samples. SO exists in the form of oil droplets in hardened cement pastes and inhibits the relaxation of water pressure at freezing. This is a probable cause for why SO decreases frost resistance.