Efficiency of calcined kaolin and silica fume as cement replacement material for strength performance

The cementing efficiency factor k of a pozzolan is defined as the number of parts of cement in a concrete mixture that could be replaced by one part of pozzolan without changing the property being investigated, which is usually the compressive strength. This concept was proposed by Smith [1] and was initially applied in rational proportioning of fly ash concrete by using the ‘‘fly ash cementing efficiency k’’, defined such that a mass f of fly ash would be equivalent to a mass kf of cement in terms of strength development. Compressive strength is normally used as basis for the estimation of k value because it is a simple and a consistent industrial test and, moreover, can be used fairly well to assess the general quality, durability and performance of a particular concrete mixture. In essence, k is a factor that accounts for the difference between the contribution of Portland cement and fly ash to strength development.