Fresh and Mechanical Characteristics of Engineered Cementitious Composites (ECC) Modified with Nano-Silica

Abstract

Due to the growing concern about the brittleness of ordinary concrete materials and the need to implement nanotechnology in concrete materials, nano-silica-modified self-consolidating Engineered Cementitious Composites (SC-ECC) have been developed. This study has investigated the influence of nano-silica (NS) on mixes of SC-ECCs prepared with polyvinyl alcohol (PVA) fibre at 0.5%, 1.0%, 1.5% and 2.0% volume fractions. The NS was incorporated at 0%, 1%, 2%, 3% and 4%, resulting in overall SC-ECCs mixes of twenty. The mixes were maintained to comply with self-consolidating requirements by adjusting the high-range water reducer (HRWR) plasticizer amount. The spread slump, V-funnel, L-box and visual stabilization index (VSI) behaviour were implemented to ensure compliance with self-consolidating requirements based on the European Federation of National Association Representing for Concrete (EFNARC). The compressive and flexural behaviour was utilized to ascertain the mechanical behaviour of nano-silica modified SC-ECCs mixes. Findings show that the compressive strength increased when NS was added to SC-ECC mixes by up to 2% and decreased afterwards. The best mix with 2% NS and 2% PVA fibre demonstrated better compressive strength with a value of 102.53 N/mm². The flexural behaviour revealed a similar pattern as compressive strength behaviour with flexural strain at 80% crack of 164 µm/m and flexural resistance 4.30 N/mm² accompanied by ductile and multiple crack behaviour as displayed in the flexural test plots. Including nano-silica particles improved, the mechanical properties of the NS-modified SC-ECCs mix by improving fibre/matrix bonding behaviour, densifying the matrix, and prolonging the course of the fly ash (FA) pozzolanic reaction of calcium hydroxide and nano-silica from cement hydration.