Nano-modified slag-based cementitious composites reinforced with basalt pellets and polyvinyl alcohol fibers

This study presents the properties of cementitious composites incorporating 6% nano-silica with high content of slag (50% of the main binder weight) and reinforced with two fiber systems (single and hybrid). Polyvinyl alcohol (micro-PVA) and basalt fiber pellets (macro-BFP) were used at dosages of 1%, 2.5% and 4.5% by composite volume, respectively. BFP is a novel type of basalt fibers, where basalt fiber strands are coated by a polymeric resin with textured surface micro-grooves. Fresh, mechanical and durability tests were conducted to investigate the properties of these innovative composites. Besides, mercury intrusion porosimetry, microscopy and thermal studies were conducted to augment the bulk trends. The results showed that nano-silica led to improved performance at early- and later-ages in terms of flowability, hardening, refinement of pore structure, mechanical capacity, bonding with BFP, and resistance to freezing-thawing cycles. Reduction in mechanical capacity and durability was observed for composites with increasing macro-BFP (single system) dosage; however, the post-cracking flexural performance of such composites was enhanced in terms of toughness. Comparatively, adding 1% micro-PVA fibers to macro-BFP (hybrid system) in the nano-modified composites led to balanced high-performance in terms of mechanical capacity, ductility and durability to frost action, which suggests their promising potential for various field applications.