Development of Hydrophobic Concrete by Adding Dual-Crystalline Admixture at Mixing Stage

Abstract

A novel approach has been presented to add a dual-crystalline hydrophobic admixture in fresh concrete for improving hydrophobicity against chloride and harmful chemicals. Dual-crystalline material can utilise water of the fresh concrete to form crystals, but the challenge is to maintain adequate hydration and strength while improving hydrophobicity. This paper presents the results from a comprehensive laboratory investigation on the application of 1%, 2% and 8% of crystallising aqueous and cementitious hydrophobic mineral in fresh concrete. Despite the high slump in the fresh mixture, no segregation was observed in the matured concrete. There was a marginal reduction of strength when a high percentage of admixture was used. Despite this, significant reduction of water absorption was observed indicating greater hydrophobicity. The optimum performance was found in mixtures with 2%-admixture. Mixture with 2%-aqueous hydrophobic admixture revealed marginal strength gain compared to 2%-crystalline cementitious hydrophobic admixture, although water protection appears to be better in cementitious mixture.