Analysis of the Effects of Mineral Admixtures on the Strength of Mortars: Application of the Predictive Model of Feret

The introduction of fine and ultra‐fine mineral admixtures in cementing materials generates a granular effect, a physico‐chemical and micro‐structural effect and, possibly, chemical effect. To analyse the specific share of each effect, we propose to use a methodology based on a volume substitution of cement by admixtures in mixes whose absolute volume of the solid phases and workability are preserved constant and then only the effects of the particles of admixtures in the cementing phase are taken into account. We expressed the compressive strength of mortars with admixtures according to a factor of compactness by applying to the mortars the principles of the predictive model of Feret. This factor makes possible to distinguish the modifications generated by the granular effect of the admixtures on the compactness of the cementing matrix independently of the physico‐chemical and chemical effects. The specific chemical action of each admixture has been evaluated by analysing the variation of the coefficient of activity K according to the rate of the cement substitution, by applying to the studied mortars the concept of the equivalent binder and by deducing the coefficient of activity from the predictive model of Feret.