Effect of Activator Composition on the Setting Time and Compressive Srength Of Fly Ash–Lime-Based Geopolymer Paste

Authors

B.R. Ramadhan Department of Civil Engineering, Faculty of Civil Engineering, Tadulako University, Palu, Indonesia, 94118
C.J. Lonardya Department of Civil Engineering, Faculty of Civil Engineering, Tadulako University, Palu, Indonesia, 94118
A.A. Adam Department of Civil Engineering, Faculty of Civil Engineering, Tadulako University, Palu, Indonesia, 94118
S.N. Akifa Department of Civil Engineering, Faculty of Civil Engineering, Tadulako University, Palu, Indonesia, 94118
S.N. Wahidin Department of Civil Engineering, Faculty of Civil Engineering, Tadulako University, Palu, Indonesia, 94118
F.R. Payung Department of Civil Engineering, Faculty of Civil Engineering, Tadulako University, Palu, Indonesia, 94118

DOI:

https://doi.org/10.22487/renstra.v6i2.766

Keywords:

fly ash, lime, activator, dosage, geopolymer, setting time, compressive strength

Abstract

This study aims to investigate the optimal composition of geopolymer paste based on fly ash and lime to achieve ambient temperature hardening, ideal setting time, and high compressive strength. The primary materials used include Class F fly ash from the Mpanau coal-fired power plant and hydrated lime (calcium hydroxide) at 5% of the fly ash weight. The activators employed were Sodium Silicate (Na₂SiO₃) and Sodium Hydroxide (NaOH), with Na₂O dosage variations of 7.5%, 10%, and 12.5%, and activator modulus (SiO₂/Na₂O ratio) variations of 0.75, 1.00, and 1.25. The specimens were cylindrical with a diameter of 25 mm and a height of 50 mm, and compressive strength tests were conducted at 3, 7, 14, and 28 days. The results showed that the optimum setting time was achieved at a Na₂O dosage of 7.5% with an activator modulus of 0.75 and 1.00, yielding setting times of 88.67 and 60.94 minutes, respectively. The highest compressive strength was recorded at a Na₂O dosage of 10% with an activator modulus of 1.25, reaching 29.76 MPa at 28 days. These findings suggest that the composition of the alkaline activator significantly influences the early-age properties and mechanical performance of fly ash–lime-based geopolymer paste

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Published

2025-09-03

How to Cite

Ramadhan, B., Lonardya, C., Adam, A., Akifa, S., Wahidin, S., & Payung, F. (2025). Effect of Activator Composition on the Setting Time and Compressive Srength Of Fly Ash–Lime-Based Geopolymer Paste. REKONSTRUKSI TADULAKO: Civil Engineering Journal on Research and Development, 6(2), 111-120. https://doi.org/10.22487/renstra.v6i2.766