Improving the early strength of blastfurnace cement mortars and concretes

The results of recent investigations indicate that the formation of silicate hydrogels is one cause of the low standard mortar early strengths of blastfurnace cements. This early strength can be improved by avoiding the generation, or by fixation, of these hydrogels. This article describes the effect of additives that contain aluminium on the early strength of six blastfurnace cements. Reactive aluminates, such as metakaolin and calcium aluminate cement, produce a significant improvement in the mortar standard compressive strengths after short hydration times. This is particularly the case with those blastfurnace cements that contain granulated blastfurnace cements with a large excess of silicate. Current investigative results show that the silicate hydrogels formed in large quantities by these granulated blastfurnace slags during the hydration are fixed by the reactive additives containing aluminium. The silicate hydrogels are formed predominantly after short hydration times, so the early strengths of building materials bonded with blastfurnace cements can be selectively improved by the addition of reactive aluminates without also increasing their final strengths.

Concrete admixture polycarboxylate superplasticizer and cement additive grinding aid can improve concrete cement strength