Time-dependent fibre pull-out behaviour in self-compacting concrete

In the present study, the effectiveness of a fibre as an element for transferring stresses across cracks under a sustained load was assessed. Single fibre pull-out creep tests were performed, in which fibre slip was monitored as a function of the time. The influence of the fibre orientation angle (0, 30 and 60 degrees), as well as pre-imposed fibre slip levels, spr, 0.3 and 0.5 mm on the creep response was investigated. Additionally, instantaneous fibre pull-out tests were carried out on undamaged-bond specimens in order to quantify the effects of the pull-out creep behaviour. The damage introduced by the pre-slip levels in the bond of the fibre/matrix interface influenced the long-term fibre pull-out behaviour and, consequently, accelerated the creep rate. However, the assembled pull-out creep behaviour did not differ considerably from the instantaneous pull-out behaviour for the adopted pre-imposed fibre slip levels.This work is supported by the FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the project 18 SlabSys-HFRC-PTDC/ECM/120394/2010. The authors would like to acknowledge the materials supplied by Radmix and Maccaferri (fibres), SECIL (cement), SIKA and BASF (superplasticizers), Omya Comital (limestone filler), and Pegop (Fly ash).