The shear behavior of cement emulsified asphalt (CA) mortar is of importance for ensuring resilience against horizontal stresses induced by high train velocities, particularly on steep inclines, declines, or off-tracking situations where complex stress states involve principal stress planes and interactions of normal and horizontal forces. The objective of this study was to investigate the shear stress-strain characteristics of CA mortar under varying asphalt-to-cement (A/C) ratios (0.5, 0.7, 0.9), temperatures (5◦C, 25◦C, 50◦C), and loading rates (0.5, 5, 50 mm/min). This approach facilitated the elucidation of shear strength, shear modulus, and fracture energy. The findings indicate that temperature and loading rate have a significant impact on the shear behavior of CA mortar. The shear strength exhibited an increase with higher loading rates and a decrease with rising temperatures across all asphalt-to-cement (A/C) ratios. Specifically, an increase of up to 40 % in shear strength was observed when the loading rate was increased from 0.5 to 5.0 mm/min at 5◦C, while a decrease of approximately 1.47 MPa per ◦C increase in temperature was noted. As the A/C ratio increased from 0.5 to 0.7, a decrease in shear strength was observed, with a range of 30–41 % at the 45◦ angle. The results demonstrated that lower A/C ratios yielded higher shear modulus at all temperatures, with an increase of up to 44 % observed when the A/C ratio decreased from 0.7 to 0.5. Additionally, significant interaction effects were observed, indicating that the positive effect of increased loading rate on shear strength was amplified under warmer conditions due to the interaction between temperature and loading rate. Similarly, the interaction between temperature and A/C ratio influenced shear modulus and fracture energy, underscoring the intricate, nonlinear interdependencies among these factors. Fracture energy decreased with increasing A/C ratio and temperature, decreasing by 9.67 J/m² per ◦C increase, while it increased with higher loading rates. The maximum fracture energy was observed at 5 ◦C with an A/C ratio of 0.5. The ANOVA at a 5 % significance level confirmed that temperature, loading rate, and A/C ratio, as well as their interactions, significantly influenced the shear properties of CA mortar. These findings highlight the necessity of considering the combined effects of temperature, loading rate, and A/C ratio in CA mortar design and predictive models.

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