Mechanical properties of early-age concrete reinforced with different fibres

Abstract To clarify the influence of fibre incorporation on the early-age concrete performance, this study experimentally compared the mechanical properties of plain concrete (PC) with those of carbon fibre -, basalt fibre -, and steel fibre-reinforced concretes (CFRC, BFRC, and SFRC). The early-age strength evolution, the time-dependent fibre-induced reinforcing effect, and the potential mechanisms of the observed trends were analysed. Furthermore, three-dimensional predictive models for splitting tensile strength were developed by coupling fibre volume fraction and aspect ratio. The experimental results showed that fibre incorporation did not fundamentally alter the overall trend of early-age strength evolution—with both PC and FRC exhibiting a logarithmic increase in strength with curing age; the promoting or retarding effect of fibres on the strength formation of concrete was very weak, specifically not exceeding 10%; the reinforcing contribution of fibres is most pronounced at 3d or 7d and tended to decrease thereafter, which may be attributed to the intrinsic evolution of the concrete matrix and progressive fibre degradation. Finally, two types of predictive equations were proposed for the splitting tensile strength of fibre-reinforced concrete, each formulated in a unified functional form.