Experimental Investigation on Mechanical and Durability Properties of M60 Grade High-Performance Fly Ash-Based Geopolymer Concrete

Abstract

Ordinary Portland cement (OPC) production is energy intensive and emits significant amount of carbon dioxide, thus the need for sustainable alternatives in the construction industry. This study experimentally examines the mechanical properties and durability of the high-performance geopolymer concrete (HPGPC) with 100% Class F fly ash as the sole binder. Sodium hydroxide and sodium silicate solutions were used for activation of the geopolymer binder and the geopolymer specimens were oven cured at 80°C for 48 h. OPC concrete was prepared with conventional M60 grade mix proportion and water cured as a control sample for comparison. The mechanical properties evaluated were compressive strength at 7, 14, 28, 56 and 90 days and split tensile strength at 7, 14 and 28 days. Durability was tested by rapid chloride permeability test (RCPT), 5% sulphuric acid attack test and water permeability. The geopolymer concrete at 28 days showed a compressive strength of 68.58 MPa which is equal to the conventional concrete of 69.18 MPa, and a split tensile strength of 4.83 MPa was also achieved, which is equal to the conventional concrete of 5.08 MPa. The geopolymer concrete also had excellent durability, with a charge passed of 319 coulombs compared with 578 coulombs for conventional concrete. The geopolymer concrete exhibited lower weight and strength loss under acid exposure of 2.02% and 14.4%, respectively, after 90 days of exposure, while the OPC concrete exhibited weight and strength loss of 6.19% and 26.8%, respectively, after 90 days of exposure. Also, the penetration depth of water has decreased from 14.5 mm to 11.2 mm. The outcome shows that the mechanical properties of this 100% fly ash based HPGPC are also approximately equal to OPC-based test sample and the durability is better, suggesting that this material has potential as a sustainable material for high-performance structural applications.

Introduction

The text presents an experimental study on M60 high-performance geopolymer concrete (HPGPC) made using 100% Class F fly ash as a replacement for Ordinary Portland Cement (OPC). The main objective is to develop a more sustainable concrete while maintaining high mechanical strength and durability.

• Problem: Cement production generates significant CO? emissions, contributing around 7–8% of global anthropogenic CO? emissions. Therefore, reducing OPC use is important for lowering the environmental impact of construction.
• Proposed solution: Geopolymer concrete replaces OPC with industrial by-products such as Class F fly ash, activated using alkaline solutions such as sodium hydroxide (NaOH) and sodium silicate (Na?SiO?).
• Research gap: Most previous research focuses on normal-strength geopolymer concrete or blended binders such as fly ash–GGBS. There is comparatively limited experimental research on M60 geopolymer concrete using 100% Class F fly ash, particularly when both mechanical and durability properties are evaluated together.
• Materials: The study uses Class F fly ash as the sole binder, M-sand as fine aggregate, 20-mm crushed granite as coarse aggregate, and NaOH/Na?SiO? as the alkaline activator. Conventional 53-grade OPC concrete is used as the control mix.
• Mix design: The geopolymer concrete uses an alkaline solution-to-binder ratio of 0.35, with Na?SiO?/NaOH maintained at 1:1. The geopolymer specimens are oven-cured at 80°C for 48 hours.
• Testing: Mechanical properties include compressive strength and split tensile strength. Durability is assessed through rapid chloride permeability, sulphuric acid resistance, and water permeability.
• Experimental comparison: Conventional concrete is water-cured, while geopolymer concrete receives high-temperature oven curing. Tests are conducted at different ages, including 7, 14, 28, 56, and 90 days for compressive strength.
• Compressive strength results: At 28 days, conventional concrete reached 69.18 MPa, while geopolymer concrete achieved 68.58 MPa, showing nearly comparable performance. At 90 days, geopolymer concrete reached 74.86 MPa, slightly exceeding conventional concrete at 73.53 MPa.
• Key finding: Although geopolymer concrete initially develops strength differently from conventional concrete, high-temperature curing promotes rapid geopolymerization and formation of a dense aluminosilicate matrix, resulting in strong long-term performance.

Conclusion

This experimental study examined the possibility of preparing M60 grade high-performance geopolymer concrete with 100% fly ash as the sole binder and performance compared with the conventional M60 grade OPC concrete in terms of mechanical and durability properties. From the experimental results, following conclusions can be drawn: 1) The 100% fly ash-based geopolymer concrete achieved a compressive strength of 43.47, 60.49, 68.58, 71.12, and 74.86 MPa at 7, 14, 28, 56, and 90 days, respectively. At 28 days, its compressive strength was comparable to that of conventional concrete, while at 90 days the geopolymer concrete slightly exceeded the conventional concrete strength of 73.53 MPa. 2) The split tensile strength of geopolymer concrete increased from 3.65MPa at 7 days to 4.83MPa at 28 days. The obtained tensile strength was found to be around 4.9% lesser than conventional concrete, which is still acceptable for M60-grade high-performance structural concrete. 3) The geopolymer concrete was found to have better chloride resistance. The RCPT result at 28 days was 319 coulombs, compared to 578 coulombs for conventional concrete, a significant difference which means that it has a very low permeability classification. 4) The sulphuric acid attack resistance of the fly ash based geopolymer concrete was enhanced significantly. The geopolymer concrete showed a weight loss of 2.02% and strength loss of 14.4% after 90 days\' exposure to 5% H?SO?, while OPC concrete showed weight loss of 6.19% and strength loss of 26.8% under the same conditions. This enhancement is attributed to the high density of the aluminosilicate matrix and low calcium content of the geopolymer binder. 5) The water permeability results further confirmed the denser microstructure of geopolymer concrete. During the test, the water penetration depth of geopolymer concrete was 11.2 mm, whereas conventional concrete was 14.5 mm, which is roughly 22.8% less water penetration in geopolymer concrete. In general, it can be concluded that the M60 grade geopolymer concrete can be prepared with 100% fly ash as geopolymer binder, which has similar mechanical properties to the conventional OPC concrete and significantly better durability properties. The need for 48 h oven curing at 80°C makes the investigated mixture especially interesting for pre cast and controlled production environments. Hence, 100% fly ash based HPGPC is a promising low cement alternative and the potential low carbon option for high-performance structural applications where better resistance to chloride ingress, attack by acids and water penetration is needed in aggressive environment.

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Copyright © 2026 Ganraj Malhari Ghule, V. M. Bogar. 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.