Study on the Effect of Interfacial Modification on the Properties of Super Standard Mica Sand Cement-Based Materials

Mica is a harmful substance in sand and occurs frequently. The application of super standard mica sand is a difficult problem in large-scale engineering. In this work, the effects of an interface modifier, mineral admixture, and a curing system on the properties of cement-based materials with super standard mica sand were studied. The strength of cement-based materials linearly decreases with the mica content in sand. When the mica content in sand exceeds 6%, the compressive strength of mortar and concrete at 28 d decreases by more than 22.3% and 33.5%, respectively. By adding the silane coupling agent (SCA) of 50% mica mass and curing in natural conditions, the compressive strength of mortar increases by 10.9%. The cement-based materials with the SCA are more suitable for curing in natural conditions, and the performance of the SCA will not be affected by adding appropriate amounts of mineral admixture. The drying shrinkage strain of the concrete, with the sand containing high mica content modified by SCA, is reduced by 10.5%, and the diffusion of chloride ions in concrete is reduced. The XRD results show that the addition of the interfacial agent does not change the hydration products. The MIP and SEM results show that the SCA can form a bridge structure between the hydration products and the mica, improve the bonding strength of the interface zone, and reduce the number of harmful pores.

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