Insights into freezing temperature and rubber content in the dynamic properties of expansive soil–rubber mixtures

• Rubber effectively mitigates damage under cyclic loads by resulting in a more elastic behavior and less energy storage under frozen temperature and cyclic loading. • RES’s shear stress and shear modulus at T = -15°C are greater than those of different plain expansive soils. • RES damping ratio at room and negative temperatures shows an opposite trend with the increase of shear strain and rubber content. Expansive soil is a widely distributed “problem soil” that exhibits significant swelling and shrinkage characteristics influenced by temperature. The coupling effect of overlying dynamic load and temperature often leads to subgrade collapse and geoengineering diseases, such as foundation instability. To alleviate the adverse effects of freezing damage in expansive soil engineering, this study introduces waste rubber as a physical modification material because of the advantages of rubber, such as its low density, excellent elasticity, and damping ratio. The behavior of rubber-reinforced expansive soils (RES) at different temperatures was explored using low-temperature dynamic triaxial tests. Representative results indicate the following: (1) The hysteresis loop of RES is closed to a high degree in the frozen state, which effectively reduces plastic deformation under load. (2) The shear stress of RES significantly increases with the decrease in freezing temperature, especially at temperature (T) = −15°C and rubber content (RC) = 28%, and it is 30.7% higher than that of plain expansive soil. (3) The parameter G 0.05 is introduced to characterize the mixture resistance to shear deformation. For T > −5°C, the G 0.05 of RES is higher than that of plain expansive soils and is closely associated with the unfrozen water content and the number of ice crystals in the sample. (4) At room temperature, rubber significantly enhances the mixture’s damping ratio, and this effect exhibits a positive correlation with the RC. However, under subzero temperature conditions, the damping ratio’s variation with RC and shear strain is the opposite of that at room temperature. Specifically, at T = −15°C, the damping ratio decreases with an increase in RC. At the tested strain range, the damping ratio amplitude for the different RCs decreases on average by 16.0%, 14.9%, and 12.2%.