Performance of self compacting concrete modified with wollastonite fibre and silica fume

Abstract

Self-Compacting concrete (SCC) offers excellent workability without vibration but often suffers from high shrinkage and durability concerns due to elevated powder content and low water to powder ratio. This study investigates the synergistic effect of wollastonite powder (WP) and silica fume (SF) as partial replacements for Ordinary Portland Cement (OPC) to enhance SCC’s performance and sustainability. Seven SCC mixes were developed with 6 % SF fixed by weight of cement, while WP, exhibiting fibrous morphology, was used as a partial cement replacement at 5 %, 10 %, 15 %, 20 %, 25 % and 30 % by weight of OPC. A constant water to powder ratio of 0.368 was maintained. Fresh properties were evaluated via slump flow, L-box, V-funnel and J-ring tests following EFNARC limits. The optimal mix, with 20 % WP and 6 % SF, achieved a 90-day compressive strength of 45.11 MPa, representing an 18.4 % increase over the control. Flexural and split tensile strengths also improved significantly due to matrix densification and crack bridging by acicular wollastonite particles. SEM analysis confirmed reduced porosity and stronger interfacial transition zones. Beyond 20 %, higher WP content led to agglomeration and strength reduction. The combination of WP and SF enhances mechanical properties while reducing OPC consumption, contributing to sustainable concrete production. This optimised SCC mix is suitable for applications involving congested reinforcement and pre-cast elements. Future work should explore long term durability and pore structure quantification.