Integral hydrophobic concrete without using silane

The high cost of silane and siloxane based water repellent agents limits their large scale applications in concrete. In the present work, a low cost waterborne stearic acid emulsion (SAE) was introduced to improve the water repellent properties and corrosion resistance of cement mortar (CM). Compared with the unmodified cement paste (CP), the introducing of SAE in CP generally reduced the fluidity and setting time, but increased the standard consistency water consumption of the CP. The CM modified with 1.0 wt% SAE exhibits integral hydrophobicity, with contact angles larger than 130° on both the as-prepared surface and the fractured surface (inner surface). The hydrophobic surface of the SAE modified CM is robust against mechanical damages. In addition, compared with the control sample, the water absorption of the modified CM decreased by 86.06%, while the corrosion resistance against chloride ion increased significantly. Moreover, the compressive strength and flexural strength of the SA modified CM decreased compared with the control sample, but the reduction was within 20%.