Characterization and nano-engineering the interface properties of PVA fibers in strain-hardening cementitious composites incorporating high-volume ground-glass pozzolans

In the context of enhancing concrete ecoefficiency through the valorization of domestic materials into concrete design, increasing research attention is being paid to the development of strain-hardening cementitious composites (SHCC) with various supplementary cementitious materials (SCM) in replacement of the commonly used fly ash (FA). In this regard, ground-glass pozzolans [or simply glass powder (GP)] obtained by grinding post-consumer waste glass can shape a potential candidate. This study is aimed at characterizing the interface properties of polyvinyl-alcohol (PVA) fibers in SHCC incorporating high-volume GP (HVGP) at 0-100% replacement of FA. Single-fiber pull-out tests were conducted to characterize the interface properties [frictional bond (tau(0)), chemical bond (G(d)), and slip-hardening coefficient (beta)] necessary for micromechanical tailoring of SHCC. Results indicate that with higher matrix compactness obtained using GP, tau(0) increased significantly, while G(d) slightly decreased. Whereas higher tau(0) in HVGP-SHCC was found to increase the maximum pull-out load of PVA fibers, excessive tau(0) causes fiber damage, thereby adversely affecting composite ductility. Therefore, a novel approach was adopted herein to nanomodify SHCC matrix as well as fiber/matrix interface by incorporating nanoscale cellulose filaments (CF) at rates of 0.03-0.10% per cement mass. This allowed to significantly alter the pull-out behavior whereby tau(0) and G(d) were relatively attenuated, while a significant increase in beta(similar to 1.0-1.5) was obtained. Thus, the incorporation of CF imparted a characteristic slip-hardening effect that contributed towards enhancing the strain-hardening capacity in HVGP-SHCC as experimentally validated by uniaxial tensile tests. (C) 2019 Elsevier Ltd. All rights reserved.