Abstract：In order to explore the sulfate erosion mechanism of silica fume lightweight aggregate concrete under dry-wet cycle conditions, pumice stone in Inner Mongolia and Linger County was selected to replace 6% cement with silicon powder. Through using NMR technology, the pore change law of silica fume lightweight aggregate concrete under the coupling effect of sulfate erosion and dry wet cycle was analyzed. The pore change law of concrete under the combined action of sulfate erosion and dry-wet cycles, and the change of concrete microscopic morphology was observed by scanning electron microscope technology, and the phase analysis was carried out by XRD. The studies results show that: during the sulfate erosion process, the mass loss rate of silica fume group and ordinary group have the same change, and the inflection point appears at 60 times. After 90 cycles, the maximum pore of silica fume group is reduced by 56.5%, and the maximum pore of ordinary group is reduced by 18.8%, which proves that the incorporation of silica fume can effectively refine the size. The harmless pores of the two groups of concrete at the beginning of the cycle are less than 10%, and there is a tendency of small pores to develop into large pores during the cycle. The gypsum and AFt generated in the pores can be seen in the SEM scanning electron microscope photos, and the slender cracks inside the concrete after 90 cycles can be observed. After 90 cycles, two groups of concretes have more CaSO4·2H2O diffraction peaks, and the products are mostly sulfate and carbonate crystal hydrates. The research results can provide a theoretical reference for the engineering construction of hydraulic structures in a sulfate environment.
