Research on frost resistance of desert sand + machine-made sand blended concrete and life prediction
Li Gong, Xuehao Zhao, Yanzhong Bu, Tianle Xu, Xingbo Yu, Yuting Liang
Abstract
In order to mitigate the harm to the ecological environment caused by the overexploitation of river sand and machine-made sand and the continuation of desertification, this study carried out a freeze-thaw cycling test on concrete with desert sand admixture as a variable and comprehensively analyzed and evaluated the frost resistance of concrete with different admixture proportions of desert sand and machine-made sand in terms of the mass loss rate and the relative dynamic elastic modulus (RDEM) on the macroscopic scale, and the nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) on the microscopic scale. The results showed that the best frost resistance of concrete was achieved when the desert sand admixture was 40 %. With the increase in the number of freeze-thaw cycles, the mass loss decreases and then increases, and the RDEM all shows a decreasing trend. Through NMR and SEM, it can be seen that the introduction of desert sand can optimize the internal pore structure of concrete and reduce the number of pores to a certain extent, and the minimum porosity (1.73 %) occurs when the dosage is 40 %, and the percentage of large pores and fissures in the interior of DS40-MS60 specimens grows only by 3 % and 2 % at the end of the freeze-thaw cycle test, which is the smallest increase. Finally, the durability deterioration model of desert sand concrete was established by using the Weibull function, and it was determined that the concrete with 40 % desert sand mixing had the least damage, and its frost durability life could reach 104.24 years. The results of the study can provide theoretical reference for the durability design of hydraulic concrete structures in cold and arid regions.