Abstract
Abstract In this study, the influence of nano-CaCO3 (NC) and nano-SiO2 (NS) on engineering properties of cementitious composites reinforced with polyvinyl alcohol (PVA) fibers was investigated including slump and fracture properties as well as compressive, flexural, tensile, and strengths. The influence mechanism of NS content on properties of cementitious composites was revealed. The combined effects of NS and NC were evaluated on the composites made with 0.9% volumetric PVA fiber addition. The experimental results showed that the addition of nanoparticles decreased the workability of fresh cementitious composites reinforced with PVA fibers. Higher NS content deceased more workability and NC reduced more workability than NS for the composites. There was an initial increase and later decrease in compressive and flexural strengths as NS content alters from 0% to 2.5%, while the continuous increase was found in tensile strength. 1.5% NS maximally increased compressive strength and flexural strength, while 2.5% NS is optimal for tensile strength. The composite containing NC exhibited lower strengths than the composite containing the same content of NS. The fracture energy, initiation, and unstable fracture toughness slightly increased with the NS content varying from 0% to 1.5%, while they reduced when NS content was higher than 1.5%. The effects of NS and NC on fracture energy and toughness were inapparent. The failure mode of PVA fibers in the tensile strength test was changed from pull-out to fracture with the addition of NS based on microstructure characterization.
Highlights
While traditional cementitious composites have found many applications in global infrastructure, they do come with some challenges including low ductility and high fracture tendency [1,2]
Such effect was due to less water retained on the NS surface caused by more water absorption on its large surface area [45]
The gels formed by rapid reactions between dissolved alkalis and NS had a high capacity of water retention [46]
Summary
While traditional cementitious composites have found many applications in global infrastructure, they do come with some challenges including low ductility and high fracture tendency [1,2]. The previous research work indicates that with PVA fiber addition, the porosity of cement paste was increased resulting in the reduction of bond strength and the engineering properties [14,15]. A 38% increase in tensile strength of the cement pastes containing 2% nanoparticles was obtained by Gesoglu et al [20] These improvements in engineering properties are reportedly associated with the filling effect of nanoparticles in voids and between unreacted particles in composites, which led a decrease in total porosity [21]. Thereby, to understand the influence of nanoparticles on engineering properties of composites containing PVA fibers is essential to improve the bonding strength between the PVA fiber and the cementitious matrix.
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