The force caused by the difference of thermal expansion coefficient between concrete aggregates at ultra-low temperature will inevitably affect the structure and should be considered in the structural design. The coefficient of thermal expansion of cement mortar and stone was measured by resistance strain gage test technology in ultra-low temperature environment, and the variation law of average linear expansion coefficient with temperature was obtained. The results show that the thermal expansion coefficients of cement mortar and stone have similar variation rules with the change of temperature. The stress state of cement mortar and stone under ultra-low temperature does not affect their thermal expansion coefficient. Thermal expansion coefficient of cement mortar under ultra-low temperature is affected by size effect.

This paper introduces the structure and application method of the self-designed ultra-low temperature mechanical loading test chamber, which can be used to study the coupling effect on building materials induced by temperature change and mechanic force. The results show that the lowest temperature in the chamber can reach to - 169 °C, which can cool the building materials to any specified temperature within 20°C and -169°C. The chamber has the functions of accurately controlling the temperature in the chamber and changing the force on the specimen independently, so that the specimen can always be in the coupling effect induced by temperature change and mechanic force. And the coupling correlation between such two effects can be tested by the device outside of the chamber.