Development of sustainable steel fibre-reinforced dry ultra-high performance concrete (DUHPC)

Abstract

Dry concrete technology has been extensively utilized in many engineering fields thanks to its remarkable high early strength, fast construction speed and low production cost. However, its shortcomings such as low flexural tensile strength, poor toughness, and susceptible to crack under stress and temperature also render the safety and service life of concrete structures unable to be effectively ensured. Dry ultra-high performance concrete (DUHPC), a promising building material, has improved mechanical and durability performance, and contributes to economical construction by reducing the cross-section size and improving structural long-term serviceability. In this study, the mechanical performance (such as compressive and indirect tensile behaviour) of fibre-reinforced DUHPC (FR-DUHPC) was experimentally investigated after a benchmark mix proportioning was determined via orthogonal tests. Different steel fibre volume contents (0.5–2.0%) and curing regimes including normal-temperature water curing, moist/steam curing and hot-water bath curing were used to explore their impacts on the mechanical properties of DUHPC. In total, 648 FR-DUHPC samples were fabricated and tested for determining their unit weight, compressive, flexural and split tensile strengths. The samples’ failure modes after bending and split tensile tests were analyzed. The results indicated that the fibre addition exhibited a notable positive effect on the mechanical properties of DUHPC, especially for the enhancement of the flexural and split tensile strengths, along with the improvement of post-cracking behaviour. An evident increase in early strength was found via using moist/steam and hot-water bath curing regime, but the former negatively impacted the development of the long-term strength. 50 °C moist/steam curing temperature was suggested for consolidating the pre-cast DUHPC units based on the microstructure analysis conducted, and the volume content of 1.5% was considered to be the most suitable steel fibre addition in this study. In conclusion, the use of supplementary cementing materials and steel fibres endows the developed FR-DUHPC wtih the advantages of both dry concrete and UHPC and achieves the target of sustainable development.