Sorptivity of fly ash concretes

A factorial experiment was designed to measure the sorptivity of cement and fly ash concretes in order to compare the durability of fly ash concrete against the cement concrete. Sorptivity measurements based on the capillary movement of water was made on three grades of cement concrete and six grades of fly ash mixes. The effect of curing was also studied by treating the samples in two curing conditions. A functional relationship of sorptivity against the strength, curing condition and fly ash content has been presented. The results were useful to analyse the factors influencing the durability of cement and fly ash concretes and to explain why some of the previously reported findings were contradictary. Curing conditions have been found to be the most important factor that affected the durability properties of fly ash concrete. When proper curing was provided, a mix with 40% fly ash was found to reduce the sorptivity by 37%. Under inadequate curing the sorptivity was found to increase by 60%. The influence of curing on cement concrete was found to be of much less importance.