Performance of nano silica-modified cementitious composites reinforced with basalt fiber pellets under alkaline and salt-frost exposures

Abstract

This study investigated the performance of nano silica-modified cementitious composites incorporating basalt fiber pellets (BFP), an emerging type of macro-fibers, under aggravated (alkaline and salt-frost) exposures relative to a reference exposure (moist curing). The composites comprised plain (cement) and blended (50% fly ash or slag replacement of cement) binder systems without/with nano silica and reinforced with two BFP dosages (2.5% and 4.5% by volume). The change of composites' physico-mechanical properties for both un-cracked and pre-cracked specimens were assessed under the three exposures. Furthermore, microstructural, thermal and mineralogical analyses were conducted to interpret the bulk trends. The results revealed that the alkaline exposure provided favorable conditions for the binders’ reactivity and hence microstructural development of the matrix; however, this was accompanied by reduction of ductility for un-cracked and pre-cracked specimens due to degradation of BFP. The matrix of the composites deteriorated physically and/or chemically under the salt-frost exposure, albeit to different extents according to the type of binder, especially for the pre-cracked specimens, the BFP remained intact though. The synoptic findings from this study highlighted the superior durability of the nano silica-modified cement-based (N-GU) and slag-based (N-G) composites reinforced with 2.5% or 4.5% BFP in harsh exposures.