On Effects of Fly Ash as a Partial Replacement of Cement on Concrete Strength

Abstract

As a part of a large research program aiming at the cementitious materials containing recycled materials at Central Queensland University – Australia, the current paper presents the preliminary results of a study on the effects of fly ash, which is used to replace cement in concrete, on the concrete compressive strength. For this purpose, systematic experiments have been carried out to investigate the influences of fly ash ratio and age. The compressive strength of concrete specimens with replacement ratios of 15%, 30% and 45%, and aged 7 and 28 days are measured and are compared with those of the concrete specimens without fly ash at the same ages. The results demonstrate that the strength of fly ash containing concrete improves more slowly but more strongly with aging, than their fly ash free counterparts, and an optimum fly ash replacement ratio exists where the maximum compressive strength of fly ash containing concrete can be achieved, and the maximum strength for the specimens aged 28 days and above is higher that of fly ash free concrete. Furthermore, the observation strength behaviours are analysed and discussed in terms of the influences of fly ash on interface reactions and interface bonding strength.

Concrete Mix Strength and Permeability with Various Supplementary Cementitious Materials

“…There has been a growing interest in using fly ash in concrete in recent years due to the economic, environmental, and technical benefits associated with its use [5]. While the use of FA in concrete is known to produce positive results, such as enhanced concrete performance, there is one undesirable aspect to consider: the rate of strength development in FA concrete is low during its early stages, which could limit its use in constructing high-strength concrete structures.…”