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In this paper, an overview focusing on the bond behavior of recycled coarse aggregate concrete (RAC) with steel bar is carried out. The results show that the failure modes of RAC specimen were not only influenced by a single factor, it is necessary to comprehensively consider the influence of various factors on the failure modes of RAC specimen; The steel bar diameter, the concrete cover to diameter ratio and the replacement rate of RCA all affect the load-slip curve of RAC specimen; Bond strength predictive equations and bond-slip relationship models of RAC with steel bar has been summarized to ensure engineers to better understand their applicability; The influencing factors of the bond behavior of RAC specimens including the replacement rate of RCA, the concrete compressive strength, the steel bar type and steel bar diameter, the steel bar embedment length and the aggregate performance; The freeze-thaw cycles and the steel bar corrosion all affect the bond behavior of RAC with steel bar. When freeze-thaw damage and steel bars corrosion reach a certain degree, the bond behavior of RAC with steel bar deteriorates.

Freeze–thaw cycles and steel reinforcement corrosion can damage the properties of concrete structures in a frigid marine environment. In this paper, experimental and analytical research on the freeze–thaw resistance of recycled coarse aggregate concrete (RAC) and the bond performance of corroded steel reinforcement and RAC after freeze–thaw cycles was conducted. The results showed that the ultimate bond strength decreases with increasing freeze–thaw cycles and steel reinforcement corrosion rates, and the bond strength decreases more rapidly under the coupled effect of freeze–thaw cycles and steel reinforcement corrosion. Additionally, the quantitative analysis of the relationships between the ultimate bond strength and different freeze–thaw cycles and steel reinforcement corrosion rates was conducted through the relativity analysis, and analysis results revealed that freeze–thaw cycles have a more pronounced effect on the ultimate bond strength than steel reinforcement corrosion. A modified bond–slip prediction model of corroded steel reinforcement and RAC after freeze–thaw cycles was established, and the model exhibited better agreement with the test data of this and other research, demonstrating its rationality and applicability. These research results can provide experimental and analytical support for freeze–thaw-resistant design and bond performance prediction of RAC structures in a frigid marine environment.

In this study, in order to study the freeze-thaw resistance of wet-mix plaster mortar after replacing artificial sand (AS) with full-component recycled sand (FCRS) and recycled brick powder (RBP) instead of fly ash (FA), ratio of binding material to fine aggregate (RBMFA) (1:5, 1:6 and 1:7), types of fine aggregate (TFA) (AS and FCRS) and kinds of mineral admixture (KMA) (FA and RBP) were considered as research variables. RBMFA, TFA and KMA have an effect on freeze-thaw resistance performance of wet mixed mortar (WMM) could be studied with the slow freezing method. Moreover, new way of application of brick powder was explored. Take advantage of full-component recycled fine aggregate instead of traditional AS to prepare wet mix plaster mortar (WMPM) have three meanings of saving natural resources, protecting the environment and achieving superior economic benefits. Numerical studies indicated that RBMFA is one of the most main influence factors of the freezing and thawing resistance of mortar. Under 25 freeze-thaw cycles, mass loss rate (MLR) and strength loss rate (SLR) of mortar increase with the reduction of rubber sand ratio, the average MLR of RBMFA 1:7 to 1:5 increased by 2.5%, and the average SLR increased by 7.4%. Replacing AS with FCRS and replacing BP with FA can not only alleviate the shortage of natural sand and FA, but also it could realize the resource utilization of building waste.

Publisher Summary The chapter presents the experimental study and results of a nonlinear numerical analysis on the behavior of slender steel reinforced high-strength concrete composite columns. Eight full-scale slender columns with rectangular section are tested under axial and eccentric loading conditions. Effects of various geometric and material parameters, such as concrete strength, slenderness of columns, and eccentricity of the applied axial load are studied in the chapter. Significant gains in load capacity are obtained with increased concrete strength for the column subjected to axial load, but the capacity is not strongly influenced by the strength of concrete for the column subjected to eccentric load. The capacity is reduced with increased slenderness ratio and eccentricity. The chapter presents a numerical method for the analysis of pin-ended slender columns. This method, considering material and geometric nonlinearities, is applicable for determining the material failure load or the buckling failure load of a slender steel reinforced concrete composite column. The predicted failure loads are closer to the experimental values.