Application of sisal fiber powder in ultra-high performance concrete: A renewable material for mitigating autogenous shrinkage

Ultra-high performance concrete (UHPC) has high autogenous shrinkage, greatly raising the risk of cracking. This study innovatively proposed the use of sisal fiber powder (SFP) to mitigate the autogenous shrinkage of UHPC. The influence of SFP on the fresh properties, heat of hydration, autogenous shrinkage, internal relative humidity, mechanical properties, and microstructure of UHPC were investigated and discussed. The results showed that the yield stress and plastic viscosity of fresh UHPC were increased by 33.5∼291.1 % and 17.7∼31.6 % after adding 1–3 vol % SFP and adding SFP significantly reduced the hydration heat release rate of UHPC. The 7 d autogenous shrinkage was decreased by 59.0 % after incorporating 3.0 vol % SFP. Moreover, adding SFP significantly increased the porosity of UHPC, hence the compressive and flexural strength was reduced by 4.2∼15.0 % and 8.2∼17.0 % respectively. However, the internal curing effect induced by SFP enhanced the late hydration and the average length of C-S-H. Finally, the nanoindentation results indicated that the elastic modulus of the UHPC matrix around SFP was improved. The results of this study verify the feasibility of SFP as an internal curing material to reduce the autogenous shrinkage of UHPC and provide a theoretical basis for the future practical engineering application of SFP in UHPC.