Bond–slip behaviour between self-compacting concrete and carbon-fibre-reinforced polymer sheets

Abstract

The bond–slip behaviour between self-compacting concrete (SCC) and carbon-fibre-reinforced polymer (CFRP) sheets was investigated using double shear pull-off concrete specimens. Concrete blocks of size 150 × 150 × 100 mm were made from two aggregate types (limestone and basalt), two aggregate gradations (12 mm and 19 mm) and three water-to-cement (w/c) ratios (0·30, 0·35 and 0·40). CFRP sheets were attached to the concrete specimens using three different bond widths (50, 100 and 150 mm) and four bond lengths (60, 80, 100 and 120 mm). The ends of the CFRP sheets were adhered to the concrete specimens at two parallel sides using a special epoxy; the middle was left free for the wrapping of an aluminium cylinder of 100 mm diameter before pull-off testing. The obtained results and literature data were employed in the development of a statistical model to estimate the ultimate shear strength and slippage between CFRP sheets and SCC. The results showed that the effect of aggregate type is insignificant, although the basalt aggregate samples showed higher bond strength and corresponding slippage than the limestone samples. The trend behaviour of the bond–slip curves for double shear pull-off specimens showed no noticeable difference between SCC mixtures made from two different aggregate gradations, but the resulting values showed a slight increase in bond strength and slippage for the concrete specimens made from the larger aggregate particles. Water-to-cement ratio was found to have a significant effect on bond strength and corresponding slippage: bond strength and slippage increased with a reduction in w/c ratio. There was a noticeable decrease in bond stress and a noticeable increase in corresponding slippage for increasing bond length and bond width. The statistical model developed shows an excellent fit to the data used, as indicated by high coefficients of determination.