Effect of mineral additions on the microstructure and properties of blended cement matrices for fibre-cement applications

Abstract

This detailed study of the effect of three mineral additions (limestone, rice husk ash and activated coal mining waste) differing in composition and properties explored the behaviour of blended cements with a 25% replacement ratio. The aim was to select the optimal addition for improving the performance of natural fibre-reinforced cements. The pozzolanic, physical and mechanical properties as well as the pore structure of the blended cement matrices were examined. The findings showed that although rice husk ash is characterised by high pozzolanicity, it had a less favourable effect on the cement than expected, yielding porous, poorly compacted and hence weak matrices. The activated coal mining waste showed better performance, reaching similar strength to control mortar, better pore size refinement and an important reduction in mean pore size of 60% compared to control mortar after 60 days of curing. In light of those findings, this aluminosilicate addition is proposed as the most apt of the three studied for improving the quality of fibre-reinforced cements, keeping in mind that the interaction effect amongst the three mineral additions was not considered in the present work.