Temperature sensitivity and model of stress relaxation properties of cement and asphalt mortar

• The stress relaxation process of CA mortar at different temperatures was elaborated.
• The microscopic response mechanism of stress relaxation properties was analyzed.
• The glass transition region was analyzed by the isochronous stress–temperature curves.
• The established model can effectively predict the temperature sensitivity of stress relaxation properties.
• The physical meaning of model parameters was analyzed.

The stress relaxation properties of two types of cement and asphalt mortar (CA mortar) in the temperature range of −40 to 60 °C and at the initial strain of 0.1% was studied by dynamic mechanical thermal spectrometer. The results show that the stress relaxation process of CA mortar can be divided into attenuation stress relaxation stage and steady stress relaxation stage. The lower the temperature is, the higher the initial stress and residual stress are. At the same temperature, the stress relaxation rate and specific stress relaxation of type I CA mortar are larger than that of type II CA mortar, while the initial stress, residual stress and stress relaxation modulus are relatively smaller. The glass transition region of type I CA mortar characterized by the isochronous stress–temperature curves is −20 to 0 °C. The established model agrees well with experimental results, and φ, δ are dominated parameters affecting the stress relaxation of CA mortar. This indicates that the established model can effectively predict the time dependence and temperature sensitivity of stress relaxation of CA mortar. The results can provide reference for the calculation of temperature stress of CA mortar filling layer of ballastless slab track.