EXPERIMENTAL STUDY ON THE FROST RESISTANCE DURABILITY OF CONCRETE IN HIGH ALTITUDE AND COLD REGIONS

The cold regions at high altitude have the characteristics of high altitude, low temperature and large temperature difference between day and night. Under the action of freeze-thaw cycle, the concrete structure is prone to damage in the high altitude and cold regions, which affects the service life of buildings and even threatens the safety of buildings when the damage is serious. To study the working performance, mechanical properties, frost resistance durability and freeze-thaw damage mechanism of concrete in the high altitude and cold regions, four kinds of concrete specimens were produced in a bridge construction project, and the freeze-thaw cycle tests were carried out. At the same time, the Nuclear Magnetic Resonance (NMR) tests of concrete under different freeze-thaw cycles were carried out. The results show that the alpine air-entraining and water-reducing concrete has the best frost resistance durability from the perspective of macroscopic mechanical properties. At the same time, the frost resistance durability of the four alpine concrete specimens is closely related to the proportion of mesopores (<0.01 μm) and micropores (0.01 μm-0.05 μm) inside the concrete, i.e., the proportion of small pores and mesopores in the alpine concrete. A larger proportion leads to a better frost resistance of concrete.