Mechanical constitutive behavior and microstructure evolution of high ductility concrete rapid repair material at different curing ages
Lijuan Chai, Z.F. Yue, Liping Guo, Yuqing Huang, Bo Chen
Abstract
High ductility concrete rapid repair material (HDCRRM) incorporating full coal gangue fine aggregate exhibits remarkable tensile deformation capacity, making it ideal for the rapid repair of cracked concrete structures. The long-term mechanical constitutive behavior of HDCRRM is critical for the repair and reinforcement design of concrete structures. This study investigates the uniaxial compressive, tensile, flexural, and shear properties of HDCRRM at various curing ages. Microscopic technologies were employed to analyze the microstructure evolution mechanism of HDCRRM, correlating it with macroscopic properties . The results demonstrate that HDCRRM maintains a consistent mechanical failure mode and shape of the constitutive relationship curve across different curing ages. As the curing age increases, there is a notable enhancement in peak compressive stress , peak compressive strain , elastic modulus , ultimate tensile strength , average crack width, flexural strength , shear strength and peak shear strain, while ultimate compressive strain, ultimate tensile strain and peak deflection exhibit a decreasing trend. The study also develops predictive models for the compressive, tensile, and shear constitutive relationships, as well as a damage evolution model. Furthermore, design parameters for HDCRRM in structural applications are suggested. The predominant hydration products in the cementitious material are AFt, AFm, aluminum hydroxide (AH 3 ), C-S-H gel, and CH, with CaCO 3 formation induced by the carbonization of CH, independent of age. The quantity of hydration products in HDCRRM increases with curing age, as evidenced by analyses of hydration degree and non-evaporable water content. The pore structure of HDCRRM becomes denser over time. This study provides a theoretical foundation for the deployment of HDCRRM in civil engineering applications .