Bonding Evaluation of Nanosilica-Modified Slag-Based Composites Comprising of Basalt Pellets and Polyvinyl Alcohol Fibers for Shear Joints

Abstract

The interfacial bonding between precast conventional concrete (CC) segments and cast-in place high-performance fiber-reinforced cementitious composites (HPFRCC) has received significant attention for jointing applications such as shear key fillers in bridge connections. Poor bonding of materials in these connections may lead to cracking, premature deterioration, and loss of monolithic behavior among segments. Among the emerging composites, cementitious composites comprising a multiscale reactive powder (nanosilica, slag, and cement) and strengthened with single and hybrid fiber systems of basalt fiber pellets (macro-BFP) and polyvinyl alcohol (micro-PVA) were prepared for potential use in shear transfer joints. BFP is a novel class of basalt fibers, where a polymeric resin of textured surface microgrooves was utilized to encapsulate the basalt strands. The study focused on the synergetic evaluation of the mechanical (compressive strength and tensile strength) performance of HPFRCC, and its bonding capacity (slant shear, bishear, and rebar pull-out) with CC and steel rebars. The mechanical trends were corroborated using thermal, microscopy, and mercury intrusion porosimetry studies. The results indicated that nanosilica enhanced the mechanical performance and interfacial bonding with CC and steel rebars. Reduction in mechanical strength and interfacial bonding were observed for specimens comprising a higher dosage (4.5%) of BFP (single fiber system) up to 21%; however, the tensile strain-hardening behavior and rebar interfacial bonding capacity were significantly improved up to 394%, and 174%, respectively. Comparatively, 1% micro-PVA fibers with 2.5% or 4.5% macro-BFP (hybrid systems) in the nanomodified composites resulted in marked improvement in terms of their mechanical properties (up to 47%) and interfacial bonding capacity with CC (up to 82%) and steel rebar (up to 29%), which suggests their promising use as fillers for shear key bridge joints.