Key mechanical properties and microstructure of carbon fibre reinforced self-consolidating concrete

This paper presents the key mechanical properties and microstructure of different carbon fibre reinforced self-consolidating concrete (CFRSCC) mixtures. Two different water-to-binder (W/B) ratios of 0.35 and 0.40 were used to produce ten CFRSCC mixtures including 0-1% carbon fibres by volume of concrete. The key mechanical properties such as compressive strength, splitting tensile strength, flexural strength or modulus of rapture, and toughness or fracture energy of CFRSCCs were determined. In addition, the load-deflection behaviour was studied for all CFRSCCs. The microstructure of all CFRSCCs was also observed via scanning electron micrographs (SEMs) of the fracture surface to examine the distribution and failure mode of carbon fibres in self-consolidating concrete. Test results revealed that the increased amount of carbon fibres decreased the compressive strength of CFRSCC by 36.6-58.9% depending on W/B ratio and curing age. However, the higher amount of carbon fibres increased the splitting tensile strength of CFRSCC by 13.1-17% at different W/B ratios and curing ages. Also, the flexural strength and toughness of CFRSCC was increased by 3.6% and 41.4%, respectively, for 0.25% carbon fibres. The load-deflection behaviour diagrams showed that the CFRSCC with 0.25% carbon fibres had the best post-peak response under loading. Furthermore, the SEMs exhibited that the CFRSCCs with 0.35 W/B ratio were denser with lesser pores than the CFRSCCs with 0.50 W/B ratio. Carbon fibres were well-distributed in concrete when the fibre content was 0.25%. It was also observed from SEMs that carbon fibres failed either by pullout or breakage under loading.