Optimization of Geopolymer Mortar Performance Using Locally Sourced Precursors: An Experimental and Statistical Approach

Tryandi Adi Muhlis; Jauhar Fajrin; Ni Nyoman Kencanawati

doi:10.70716/reswara.v4i4.808

Authors

Tryandi Adi Muhlis Department of Civil Engineering, Mataram University, Mataram, Indonesia Author
Jauhar Fajrin Department of Civil Engineering, Mataram University, Mataram, Indonesia Author
Ni Nyoman Kencanawati Department of Civil Engineering, Mataram University, Mataram, Indonesia Author

DOI:

https://doi.org/10.70716/reswara.v4i4.808

Keywords:

fly ash, geopolymer mortar, supplementary precursor, alkaline activator, Two-Way ANOVA

Abstract

Fly ash-based geopolymer mortar is a promising alternative to Portland cement because it utilizes aluminosilicate-rich industrial by-products and reduces cement consumption. This study investigated metakaolin, calcined clay, and rice husk ash as supplementary precursors and four NaOH/Na₂SiO₃ ratios (1:1.5, 1:2, 1:2.5, and 1:3) on the density, water absorption, and compressive strength of fly ash-based geopolymer mortar. A full factorial experimental design (3 × 4) was employed, with five specimens for density and compressive strength testing and three specimens for water absorption testing. Raw materials were characterized using X-ray fluorescence, and mortar properties were evaluated at 28 days. The data were analyzed using Two-Way Analysis of Variance at a 5% significance level, preceded by the Anderson–Darling normality test. Tukey’s Honestly Significant Difference test was applied to significant main effects. The results showed that supplementary precursor type and NaOH/Na₂SiO₃ ratio significantly affected compressive strength and water absorption (p < 0.05), whereas neither factor significantly affected density. No significant interaction was observed between the two factors for any evaluated property. The highest observed compressive strength was obtained by the metakaolin mixture at a NaOH/Na₂SiO₃ ratio of 1:2.5, reaching 18.01 MPa. Although the calcined clay mixture at the same ratio exhibited the highest observed density (2.22 g/cm³), density was not significantly affected by either factor. These findings demonstrate that precursor type and alkaline activator ratio significantly influence compressive strength and water absorption, while their effects on density and interaction are not statistically significant.

References

Albidah, A., Alghannam, M., Abbas, H., Almusallam, T., & Al-Salloum, Y. (2021). Characteristics of metakaolin-based geopolymer concrete for different mix design parameters. Journal of Materials Research and Technology, 10, 84–98. https://doi.org/10.1016/j.jmrt.2020.11.104

Aouan, B., Alehyen, S., Fadil, M., EL Alouani, M., Khabbazi, A., Atbir, A., & Taibi, M. (2021). Compressive strength optimization of metakaolin‐based geopolymer by central composite design. Chemical Data Collections, 31. https://doi.org/10.1016/j.cdc.2020.100636

Archer de Carvalho, T., Gaspar, F., Marques, A. C., & Mateus, A. (2024). Optimization of formulation ratios of geopolymer mortar based on metakaolin and biomass fly ash. Construction and Building Materials, 412. https://doi.org/10.1016/j.conbuildmat.2023.134846

Aslan, S., & Erkan, İ. H. (2024). The Effects of Fly Ash, Blast Furnace Slag, and Limestone Powder on the Physical and Mechanical Properties of Geopolymer Mortar. Applied Sciences (Switzerland), 14(2). https://doi.org/10.3390/app14020553

ASTM International. (2019). ASTM C618/C618M-19: Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. West Conshohocken, PA: ASTM International. https://doi.org/10.1520/C0618_C0618M-19

Athira, R., & Sathyan, D. (2026). Data-driven optimization of fly ash–slag–rice husk ash geopolymer systems via particle packing and thermodynamic simulation. Journal of Asian Architecture and Building Engineering. https://doi.org/10.1080/13467581.2026.2665973

Barbhuiya, S., & Pang, E. (2022). Strength and Microstructure of Geopolymer Based on Fly Ash and Metakaolin. Materials, 15(10). https://doi.org/10.3390/ma15103732

Boakye, K., & Khorami, M. (2023). Impact of Low-Reactivity Calcined Clay on the Performance of Fly Ash-Based Geopolymer Mortar. Sustainability (Switzerland), 15(18). https://doi.org/10.3390/su151813556

Davidovits, J. (2020). Geopolymer chemistry and applications (5th ed.). Geopolymer Institute.

Hadi, M. N. S., Al-Azzawi, M., & Yu, T. (2018). Effects of fly ash characteristics and alkaline activator components on compressive strength of fly ash-based geopolymer mortar. Construction and Building Materials, 175, 41–54. https://doi.org/10.1016/J.CONBUILDMAT.2018.04.092

Hwang, C. L., & Huynh, T. P. (2015). Effect of alkali-activator and rice husk ash content on strength development of fly ash and residual rice husk ash-based geopolymers. Construction and Building Materials, 101, 1–9. https://doi.org/10.1016/j.conbuildmat.2015.10.025

Karyawan, I. D. M. A., Yuniarti, R., Hasyim, H., & Widianty, D. (2022). Characteristics of fly ash geopolymer based on alkaline ratio of activators for building materials: A review. Teknika: Jurnal Sains dan Teknologi, 18(1), 18–22. https://doi.org/10.36055/tjst.v18i1.15410

Lehne, J., & Preston, F. (2018). Making concrete change: Innovation in low-carbon cement and concrete. Chatham House.

Lekshmi, S., Sudhakumar, J., & Thomas, S. (2023). Durability performance of geopolymer mortar containing high calcium fly ash and low-grade waste clay. Asia-Pacific Journal of Science and Technology, 28(2), APST–28. https://doi.org/10.14456/apst.2023.20

Logesh Kumar, M., & Revathi, V. (2016). Metakaolin bottom ash blend geopolymer mortar - A feasibility study. Construction and Building Materials, 114, 1–5. https://doi.org/10.1016/j.conbuildmat.2016.03.149

Matsimbe, J., Dinka, M., Olukanni, D., & Musonda, I. (2024). Durability properties of ambient-cured fly ash-phosphogypsum blended geopolymer mortar in terms of water absorption, porosity, and sulfate resistance. Discover Sustainability, 5(1). https://doi.org/10.1007/s43621-024-00537-3

Montgomery, D. C. (2019). Design and analysis of experiments (10th ed.). John Wiley & Sons.

Mulapeer, E. M., & Omar, A. H. (2025). Durability and mechanical performance of geopolymer mortar with partial replacement of fly ash by rice husk ash and variations in alkaline activator concentrations. Discover Civil Engineering, 2, Article 82. https://doi.org/10.1007/s44290-025-00234-8

Nana, A., Epey, N., Rodrique, K. C., Deutou, J. G. N., Djobo, J. N. Y., Tomé, S., Alomayri, T. S., Ngouné, J., Kamseu, E., & Leonelli, C. (2021). Mechanical strength and microstructure of metakaolin/volcanic ash-based geopolymer composites reinforced with reactive silica from rice husk ash (RHA). Materialia, 16. https://doi.org/10.1016/j.mtla.2021.101083

Harmaji, A., Haimir, A. S., & Sunendar, B. (2023). Impact of reduced activator concentration and curing method on compressive strength of metakaolin/fly ash-based geopolymer mortar. Jurnal Riset Teknologi Pencegahan Pencemaran Industri, 14(1), 19–28. https://doi.org/10.21771/jrtppi.2023.v14.no.1.p19-28

Sharmin, S., Sarker, P. K., Biswas, W. K., Abousnina, R. M., & Javed, U. (2024). Characterization of waste clay brick powder and its effect on the mechanical properties and microstructure of geopolymer mortar. Construction and Building Materials, 412. https://doi.org/10.1016/j.conbuildmat.2023.134848

Zahid, M., Shafiq, N., Nuruddin, M. F., Nikbakht, E., & Jalal, A. (2017). Effect of partial replacement of fly ash by metakaolin on strength development of fly ash based geopolymer mortar. Key Engineering Materials, 744 744 KEM, 131–135. https://doi.org/10.4028/www.scientific.net/KEM.744.131

Zhu, H., Liang, G., Xu, J., Wu, Q., & Zhai, M. (2019). Influence of rice husk ash on the waterproof properties of ultrafine fly ash based geopolymer. Construction and Building Materials, 208, 394–401. https://doi.org/10.1016/j.conbuildmat.2019.03.035