Comparing the performance of fine fly ash and silica fume in enhancing the properties of concretes containing fly ash

Fine fly ash which is obtained by classification of conventional fly ash has become available to concrete industry in recent years. In the current research the possibility of using fine fly ash in binary and ternary mixes with the aim of overcoming the rather slow rate of strength development in concretes containing conventional fly ashes or enhancing their durability was investigated. The results show that the rate of pozzolanic reaction of fine fly ash is only moderately higher than conventional fly ash and the water demand is slightly reduced. The results of ternary mixes show that fine fly ash is not an effective material for increasing the rate of development of properties in concretes containing slow reacting pozzolans such as conventional fly ashes. The results of tests assessing durability of concrete against chloride ingress such as RCPT, RCMT and electrical resistivity indicate that the use of this material does not improve concrete durability over that which can be achieved by conventional fly ash at equal replacement levels. (C) 2013 Elsevier Ltd. All rights reserved.