Investigations into effective fly ash used in concrete

Abstract

This work presents a study on the influence of thermal-electrical fly ash on the cement paste hydration processes, investigation into cement stone, mortar, ordinary and self-compacting concrete, when cement was replaced by fly ash (5-33%). It was estimated that cement stone and cement paste prepared from fly ash and cement properties were better when polycarboxylic superplasticiser "Visco Crete-3" was used. It was established that admixture of fly ash influences the processes of cement hydration: the amount of free Ca(OH) 2 in cement stone was decreased and amount of stable calcium hydro silicates was increased. It allows to state, that cement stone becomes more corrosion-resistant and more durable. When fly ash admixture is applied in ordinary concrete production, it is possibility to reduce cement expenditures up to 33% and in self-compacting concrete production, segregation and separation of water decreases. Data of investigations on hardened concrete showed that fly ash increases compressive strength (up to 15%), decreases shrinkage strains (up to 31,6%), increases plastic deformations (up to 38%), modulus of elasticity (up to 15%) and modifies other concrete properties.