Bond behavior of carbon-fiber yarn embedded in cement mortar

This paper deals with the influence of admixtures - silica fume, superplasticizer and air entraining agent - on the improvement of the bond strength between bundled carbon filaments and cement mortars. Pull-out tests were carried out to examine the bond between carbon-fiber yarn and various cement matrices. An overall microstructural analysis was conducted and correlated with pull-out data. Experimental results showed that all the applied admixtures contributed to improved bonding. The air entraining agent was found to be the most effective in improving the bond strength of the studied carbon-fiber reinforced cement mortar. Air bubbles formed inside the mortar mix as a result of added air entraining agent and the ones formed in the vicinity of the outer filaments of the yarn may provide a mechanical barrier at the interface, leading to a significant increase in interface friction.