Pull-out behaviour and interface critical parameters of polyolefin fibres embedded in mortar and self-compacting concrete matrixes

Polyolefin based macro-fibres have proved their good performance for the structural reinforcing of concrete with fracture behaviour comparable to that of steel fibres but being chemically stable. Their adhesion to cementitious matrix is enhanced by surface treatments and embossed shapes. However, there is a lack of research about their pull-out behaviour and microstructural interface property. In this study, pull-out tests were designed by synchronising the testing machine with a video-extensometer device. The tests were performed with polyolefin fibres embedded on mortar and self-compacting concrete specimens. Six embedded lengths were used, with their inclination varying from 0° to 60°. The results provided significant information about the pull-out load and the energy absorbed in the process. Microstructural analyses provided a detailed view of the interface between polyolefin fibre and cement paste. The continuity between CSH gel and polyolefin fibres exhibited a sound interface between polyolefin fibres and cement paste, without either voids or discontinuities.