Manufacturing of integral hydrophobic concrete (IHC) using Pickering emulsion with limited effects on mechanical strength

Abstract

The integral hydrophobic concrete (IHC) performs excellent long-term impermeability, however, accompanied with unavoidably sacrificing of its mechanical strength. The large defects induced by hydrophobic agent (HA) and the altered cement hydration are the main factors for such decline of mechanical strength. In this study, we develop emulsion additives involving the encapsulation of phase-change HA by graphene oxide (GO). Such additives can perform solid-to-liquid change adaptive to temperature increase as cement hydration undergoing. The solid state at room temperature allowed a uniform and stable mixing with cement, preventing the release and the aggregation of HA in liquid cement, thereby avoiding the formation of large defects. In addition, GO promotes the formation of hydration products around GO/MPA, which further deferred the release of HAs. As hydration undergoing, HA is released into solidified cement and cover the internal surface of pores and channels, resulting in the decrease of pore volumes and decrease of permeability. These behaviors avoid aforementioned decline factors in some extent, thereby optimizing the mechanical strength of IHC. Consequently, the IHC with 2% dosage of emulsion powders exhibits integral hydrophobicity with a contact angle of 140°, which could offer a decent resistant to water absorption. Remarkably, such IHC shows relieved strength decline of only 8% after 28 days of curing compared with reference mortar which is far lower than the best values of 31% in the reported literature. Our results demonstrate an effective method to reinforce the IHC.