Efficiency of mineral admixtures in mortars: Quantification of the physical and chemical effects of fine admixtures in relation with compressive strength

This work is the fourth part of an overall project the aim of which was the development of general mix design rules for concrete containing different kinds of mineral admixtures. The two first parts presented the separation and quantification, by means of an empirical model based on semi-adiabatic calorimetry measurements, of the different physical effects responsible for changes in cement hydration (short terms) when chemically inert quartz powders were used in mortars. Part three dealt with an intensive experimental program, presenting and commenting more than 2000 compressive strength measurements. This program concerned 1 day to 6 months old mortars containing up to 75% of inert and pozzolanic admixtures. All these compressive strength results are analyzed in this fourth part and the influence of three effects, namely dilution, heterogeneous nucleation and the pozzolanic effect, are discriminated and quantitatively evaluated. An efficiency concept is proposed in order to take into account the effect of mineral admixture in mortars from both the physical and chemical points of view. It uses an efficiency function ξ(p) that has notable properties: it is independent of time, independent of fineness and independent of the type of mineral admixture.