Study on the mechanical properties of sandstone-concrete composite interface under the dry–wet cycle action

The dry–wet cycle will cause the deterioration of rock mass and grouting materials in the anchoring system, and then affect their strength and deformation, which has an important impact on the stability and durability of geotechnical engineering. In this paper, the damage and deterioration effects of sandstone-concrete composite samples under dry and wet cycle conditions are studied by using nuclear magnetic resonance technology, and the mechanism of anchoring system under dry and wet cycle conditions is revealed. The experimental results show that rock and concrete are damaged to different degrees under the action of wet and dry circulation. The micropore content of the whole sample increased and the medium and macro pores expand continuously during the dry–wet cycle action. The cracks development with the increase of number of dry–wet cycles intensify the damage of the sandstone-concrete connection surface. It can be observed that the damage of sandstone part is much lower than that of concrete part under the action of dry–wet cycle based on NMR image. The drawing process compresses the pores and enhances the plastic ability of CRC (concrete rock composite) sample, which explains the mechanical law that the drawing force of low-strength concrete increases gradually with the increase of the number of dry–wet cycles due to the increase of the internal pores of the CRC sample.