Review of factors affecting bond between ultrahigh-performance concrete and steel fibres

Ultrahigh-performance concretes (UHPCs) have advantages over conventional concretes but suffer from brittleness owing to their high strength. The addition of steel fibres significantly overcomes this limitation by acting as a stress-transferring bridge between the matrix and the fibres, which enhances the durability and mechanical performance of the mix. For this review, data from several previous research studies were compiled in order to offer a comprehensive understanding of the varying factors influencing the pull-out behaviour and bonding characteristics between the UHPC matrix and steel fibres. The findings of this study revealed that deformed steel fibres embedded at 30° and 45° exhibit significantly greater loading rate sensitivity on the pull-out energy under quasi-static and seismic loading rates when compared with straight steel fibres. Compared with steel fibres with a low aspect ratio (i.e. 62.5), steel fibres with a large aspect ratio (i.e. 125) provided higher strain capacity (by 77%), energy absorption capacity (by 40%) and post-cracking strength (by 10%) under impact loading. The possible factors in the domain of fibre–matrix interactions of fibre-reinforced concrete are covered and discussed in this article.