# Effect of Organotin on Performance of Siloxane Materials for Surface Treatment of Cementitious Materials

## TL;DR

This paper investigates how organotin improves the surface hardness of siloxane-treated cement without affecting its waterproofing.

## Contribution

The novel finding is that organotin enhances surface hardness of siloxane-treated cement by accelerating gelation and reducing negative alkyl effects.

## Key findings

- Organotin increased surface hardness of siloxane-treated cement by 105.1%.
- Organotin accelerated siloxane gelation and consumed more portlandite in cement.
- The addition of organotin did not affect the waterproofing properties of siloxane-treated cement.

## Abstract

Surface treatment is essential for cementitious materials. Siloxane is a material that can potentially be applied in surface treatment, as it possesses the advantages of both inorganic and organic surface treatment materials for cement. Organotin, serving as a neutral catalyst, performs well in improving the performance of siloxane coating. In this work, the effect of organotin on the surface treatment performance of siloxane was studied for application in cementitious materials, including surface hardness and waterproofing properties. Organotin had little effect on the waterproofing of cement paste treated with siloxane. However, the addition of organotin positively impacted the surface hardness of cement paste treated with MTMS, which increased by 105.1%. The function of organotin was analyzed through XRD, FTIR, SEM, and pore structure characterizations. Organotin can speed up the gelation of siloxane, thus consuming more portlandite in cement. The negative effect of the alkyl group could be partially reduced by promoting the condensation of the alkoxy group. This indicated that treating siloxane with organotin is valuable for improving the durability of cement-based materials, increasing their surface hardness without affecting waterproofing.