Sustainable cement-gypsum composite with reduced ettringite expansion

Construction materials based on either Portland cement or gypsum are amongst the most popular and widely used construction materials. Their applications however may berestricted by the specific properties or economical requirements. Composite incorporating both binders could be a cheap solution for construction industry of good mechanical/physical properties. However, creation of a composite of low shrinkage and preferably small expansion based on ettringite formation may be difficult due to its high aggressiveness. The authors propose that the limitation of ettringite crystals growth may be achieved by introduction ofpuzzolanic additives in form of microsilica and methylamonic compounds,strongly bonding calcium hydroxide. Application of hexamine may further reduceettringite expansion.