ABSTRACT
Abstract Polymer fibres (mainly fibrillated polypropylene) have been used for nearly a decade in wet-mix shotcretes at addition rates varying between 0.10 and 0.66 percent by volume, i.e. 0.9 to 6 kg/m3. A new non-fibrillated polyolefin fibre has been developed which can be added to concrete and wet-mix shotcrete mixtures at considerably higher addition rates. This has been made possible because of the characteristics of the fibre (lower aspect ratio and lower specific surface area compared to fibrillated polypropylene fibres) plus a unique fibre dispensing system. A study was undertaken to assess possible addition rates of the new polyolefin fibre to wet-mix shotcretes and to evaluate the plastic and hardened properties of such shotcretes compared to a plain control shotcrete mixture with no fibre reinforcement. In this study the polyolefin fibre was added to the shotcrete at rates of 1.0 and 2.0 percent by volume (9.1 and 18.2 kg/m3). Test panels were shot from which specimens were procured for determination of compressive and flexural strength, toughness, boiled absorption and volume of permeable voids. Test results showed that good residual load carrying capacity after first crack in flexural toughness testing (toughness performance level) could be obtained at 1.0 and 2.0 percent by volume polyolefin fibre addition rates. Limitations on pumpability of the mixture with 2.0 percent by volume of polyolefin fibre however indicated that in the field fibre addition rates would likely be limited to about 1.25 to 1.5 percent by volume for the type of shotcrete equipment commonly being used in North America. Such mixtures are attractive for use in a variety of applications where toughness and control of cracking are important. Keywords: Fibre, polyolefin, shotcrete, toughness.
