MECHANICAL PROPERTIES AND MICROSTRUCTURE OF COMPOSITE BINDERS CONTAINING SHALE ASH AND FLY ASH

The microstructure and the mechanical properties of hardened mortars made of superplasticized composite binder containing shale ash and fly ash are investigated. The pozzolanic reaction consumes the oriented Ca (OH)2 crystals, thus making the transition zone dense. Appropriately proportioning of shale ash and fly ash decreases the water requirement and increases the packing density of composite binder mortars, therefore increases their strength. Super plasticizer promotes the carbonation of calcium hydrates and the formation of ettringite that is transformed gradually into mono-sulfoaluminate hydrate in composite binder mortars. The joint action of fine complex mineral admixture and super plasticizer has a synergistic effect to improve the mechanical properties of composite binder.