Assessment of high volume replacement fly ash concrete – Concept of performance index

This paper examines the practicality and suitability of high proportion replacement of cement by class F fly ash. Binary and ternary blends of fly ash/Portland cement and fly ash/silica fume/Portland cement, were tested. The investigation focussed on the realistic conditions of concrete making on site and the effects on the mechanical aspects as well as the consequences on corrosion of reinforcement. been found that class F fly ash may replace 50% of the Portland cement and at the same time result in improving resistance to chloride initiated corrosion. Such replacement however, may significantly reduce the values of the mechanical properties. Nevertheless, such concrete is considered a high performance concrete. The authors therefore suggest that the mechanical and durability characteristics of concretes may be assigned numerical Performance Index values. These values may provide the means for making informed decisions on the extent of cement replacement by other cementitious materials.