Micro-encapsulated integral water repellent for cementitious materials : Reaction of the silica shell in the cement matrix.

 
Protecting cement-based construction materials against water absorption is key to prevent some physical or chemical degradation. Silicone-based post treatment water repellent is an industry-proven method to protect cementitious material. Silane-based emulsion or powder have also been used for the last 10 years as integral water repellent but they are known to impact somewhat cement setting. A new generation of integral water repellent based on silicone resin and innovative microencapsulation technology has been developed, which is commercialised as Dowsil IE 6686. It enables to protect cementitious materials against water ingress in the bulk with yet very limited impact on cement hydration processes. Interaction/reaction of the silica shell in a cement matrix have been studied to explain the delayed release mechanism of the active material in the cement mix. A model will be proposed to explain the behaviour of this microencapsulated water repellent in the cement mixture