Mechanical, Electrical and Self-Healing Properties of Carbon Fibre-Reinforced Ultra-Lightweight ECC

The hybrid mixes of carbon fibres (CF), fly ash cenosphere and polyethylene fibre could be used to develop smart ultra-lightweight engineered cementitious composites (ULW-ECCs). In this study, the effects of CF length (1, 3, 6, 9, 12, 15, 20 mm) with different volume fractions (0.0, 0.5 and 1.0 vol%) on the fundamental mechanical (compression, tension and flexure) and electrical properties of CF-reinforced ULW-ECCs were evaluated. Pseudo-strain-hardening indices, multiple micro-cracking behaviours and self-healing properties were also tested. The experimental results reveal that, except for the 1 mm particle CF, incorporating CF could improve the strength (compression, tension and flexure) of ULW-ECCs but decrease the strain ductility properties under tension; and CF lengths of 9- and 12-mm show better results. The electrical conductivity of ULW-ECCs was improved by CF, and the higher dosage further increased the conductivity. The conductivity increased first and then decreased with the increase in CF length and the 9 mm CF (1.0 vol%) shows higher conductivity. The conductive network was affected by the volume fraction, length, count under the same content, and possible fracture of CF. Long CFs work well at low content in forming conductive networks, while short CFs are more effective at high content. The conductivity decreased with the increase of curing age and reached a constant value after 90d. Incorporating CF and increasing its length/content negatively impacted crack number and width. CF-reinforced ULW-ECCs exhibit excellent self-healing, with reduced ability as wet-dry cycles and curing age increase.