Experimental Investigation on Properties of High Strength Self Compacting Concrete

Abstract

Self-Compacting Concrete (SCC) is an advanced concrete technology capable of flowing and consolidating under its own weight without mechanical vibration, making it suitable for heavily reinforced and complex structural elements. This study presents an experimental investigation on the fresh, hardened, and non-destructive properties of High-Strength Self-Compacting Concrete (HSSCC) of grade M60 incorporating fly ash and silica fume as supplementary cementitious materials. Ordinary Portland Cement (OPC) 43 grade was partially replaced with fly ash at 0%, 10%, 15%, 20%, and 25%, while silica fume content was kept constant at 8%. A polycarboxylic ether-based superplasticizer was used to achieve the required workability, and mix design was carried out as per IS 10262:2019 and IS 456:2000. Fresh properties were evaluated using slump flow, V-funnel, and L-box tests, while hardened properties were assessed through compressive, split tensile, and flexural strength tests at 7 and 28 days. Ultrasonic Pulse Velocity (UPV) testing was conducted to evaluate internal quality. Results indicated that increasing fly ash content enhanced the workability and flowability of SCC without compromising stability. The mix with 25% fly ash achieved the highest performance, with 28-day compressive strength exceeding 70 MPa and improved tensile and flexural strengths. UPV results confirmed better density and homogeneity. The study concludes that the combined use of fly ash and silica fume is effective in producing sustainable and high-strength SCC suitable for structural applications.

Introduction

Concrete demand is increasing rapidly due to global infrastructure growth, leading to resource depletion and environmental concerns. Conventional concrete often faces compaction issues, especially in densely reinforced sections, resulting in defects and reduced durability. Self-Compacting Concrete (SCC) was developed to overcome these problems by flowing and compacting under its own weight without mechanical vibration, improving construction quality, efficiency, and working conditions. When combined with high-strength properties, SCC becomes suitable for modern structural applications. High-Strength Self-Compacting Concrete (HSSCC) further enhances performance by incorporating supplementary cementitious materials such as fly ash and silica fume, which improve workability, strength, durability, and sustainability.

This study focuses on developing M60 grade HSSCC using fly ash as a partial cement replacement and silica fume at a constant dosage. A comprehensive literature review highlights the importance of optimized mix design, the beneficial effects of fly ash on workability and long-term strength, and the role of silica fume in improving early-age strength and microstructure. The experimental program used OPC, river sand, crushed stone, fly ash, silica fume, and a polycarboxylate-based superplasticizer, with mix proportions designed according to IS 10262:2019. Fly ash replacement levels of 0%, 10%, 15%, 20%, and 25% were investigated.

Fresh property tests—including slump flow, T?? time, V-funnel, and L-box—showed that increasing fly ash content significantly improved flowability, passing ability, and stability while remaining within SCC limits. Hardened property results indicated consistent improvements in compressive, split tensile, and flexural strengths at both 7 and 28 days, with the highest performance observed at 25% fly ash replacement. Ultrasonic Pulse Velocity results confirmed improved internal quality and homogeneity. Overall, the study demonstrates that incorporating fly ash and silica fume in M60 grade HSSCC enhances workability, strength, durability, and sustainability, making it a viable and efficient material for high-performance structural applications.

Conclusion

Based on the experimental investigation, the following conclusions are drawn: 1) The experimental results demonstrate that the incorporation of fly ash in self-compacting concrete significantly enhances both fresh and hardened properties while maintaining all performance parameters within the recommended limits for SCC. 2) The fresh state characteristics improved progressively with increasing fly ash content, as evidenced by increased slump flow, reduced T?? and V-funnel flow times, and higher L-box blocking ratios, indicating improved flowability, passing ability, and segregation resistance. 3) The compressive strength of SCC increased consistently at both 7 and 28 days with higher fly ash replacement levels, with the maximum strength achieved at 25% fly ash, confirming its positive contribution to strength development. 4) Split tensile and flexural strengths exhibited a gradual improvement with increasing fly ash content, reflecting enhanced tensile resistance, improved crack control, and better interfacial bonding within the concrete matrix. 5) Ultrasonic Pulse Velocity results showed a steady increase with fly ash incorporation, indicating improved internal homogeneity, reduced voids, and a denser microstructure compared to the reference SCC mix. 6) Based on the overall evaluation of rheological behaviour, mechanical performance, and UPV characteristics, fly ash replacement of up to 25% is found to be optimal for producing high-performance and sustainable self-compacting concrete.

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Copyright

Copyright © 2026 Rijul Thakur, Dr. Hemant Sood. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.