This study investigates the hardening behavior of adhesives used in retard-bonded prestressed tendons, with a focus on establishing a quantitative relationship between aging time and Shore hardness to enable rapid on-site assessment of curing degree. Accelerated curing tests were conducted at a constant temperature of 45 °C on three adhesive series with different standard curing periods. Cone penetration, Shore hardness, and tensile shear strength were measured at regular intervals throughout the curing process. Microstructural evolution was characterized using SEM-EDX. The results show that cone penetration decreases stepwise with aging time, while Shore hardness and tensile shear strength increase monotonically. A significant linear correlation (R2 > 0.995) between Shore hardness and tensile shear strength was observed across all specimens. A novel logarithmic model is proposed to describe the evolution of relative Shore hardness as a function of relative aging time, achieving an R2 of 0.911. This model enables prediction of vadhesive hardness at any given time under 45 °C conditions, providing a practical tool for construction quality control. The findings offer a new pathway for non-destructive evaluation of adhesive curing in retard-bonded prestressed systems.
Wei et al. (Sun,) studied this question.