Influence of composite admixtures on the freezing resistance and pore structure characteristics of cemented sand and gravel

CSG shows low freezing resistance due to its poor cementing properties, and adding admixtures is the main method to improve its freezing resistance. In this paper, experiments were designed based on the Taguchi method and on the freezing resistance and pore structure characteristics of CSG after adding admixtures. After 20 freeze-thaw cycles, the results showed that both the compressive strength and dynamic elastic modulus of CSG decreased. The area occupancy of more harmful pores (>200 nm) in the NMR test increased, and the fractal dimension of the pore structure in the SEM images also increased. Based on the above indicators, it was concluded that L9 (sodium dodecyl sulfate, graphene oxide, nanosilica powder, and water-reducing agent) has the best freezing resistance. Experiments were conducted on L9 to verify that L9 can significantly improve the freezing resistance of CSG materials under different water-binder ratios, sand ratios, and cement dosages.