Effect of an expansive agent on the interfacial bond and mechanical properties of carbon fibre-reinforced cement-based composites

Improving the flexural strength of a chopped-carbon fibre-reinforced cement-based composite while promoting good workability is highly attractive for building high-rise large-span structures. This study utilized a sulphoaluminate-based expansive agent to optimize the mechanical properties of chopped-carbon fibre-reinforced cement-based composites by improving the fibre–matrix interfacial properties. The results of a single-fibre pull-out test showed that the interfacial frictional bond strength improved up to 51% owing to the addition of the expansive agent, whereas the chemical debonding energy remained nearly unchanged. The study then investigated the effects of various concentrations of the expansive agent on the strength of the cement paste containing various lengths and volume fractions of the carbon fibre. The results indicated that benefited from the expansive agent induced high interfacial bond strength, the flexural strength and fluidity of the carbon fibre reinforced cement paste could be further optimized. For example, by utilizing expansive agent, the flexural strength could be further improved by 28% for cement paste containing 0.5% carbon fibre with length of 15mm.