ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Deciphering geopolymerization kinetics of fly ash–bottom ash systems via an iso-conversional approach

Januarti Jaya Ekaputri, Vincent Sutresno Hadi Sujoto, Muhammad Olvianas, Felix Arie Setiawan, Widi Astuti, Amelia Andriani, Daniel Timotius, Kevin Cleary Wanta, Robertus Dhimas Dhewangga Putra, Ferian Anggara, and Himawan Tri Bayu Murti Petrus

Departement of Civil Engineering, Faculty of Engineering, Institut Teknologi Sepuluh Nopember, Kampus ITS, Sukolilo, Surabaya, Indonesia

E-mail: januarti@ce.its.ac.id

Received: 27 March 2026  Accepted: 15 May 2026

Abstract:

This study addresses the need for sustainable alternatives to conventional cement by utilizing fly ash and bottom ash in geopolymer concrete, while providing a deeper understanding of the underlying reaction kinetics. The objective is to evaluate the effect of bottom ash incorporation on geopolymerization behavior through kinetic modeling and material characterization. Experimental investigations were conducted using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and compressive strength testing under curing temperatures of 30–90 °C. The geopolymerization kinetics were analyzed using an iso-conversional approach, and multiple solid-state reaction models were evaluated. The results demonstrate that the third-order reaction model provides the best fit to the experimental data, as indicated by the highest correlation coefficients across different compositions and curing conditions. The incorporation of bottom ash reduces the reaction rate due to its lower reactivity and higher crystallinity, as confirmed by XRD analysis. However, an optimal composition of 25% bottom ash (75:25 ratio) achieves a compressive strength of up to 41 MPa at 90 °C, indicating a favorable balance between kinetics and mechanical performance. Furthermore, the FTIR-derived correlation parameter (Corr value) shows strong agreement with compressive strength evolution, confirming its applicability as a semi-quantitative indicator of geopolymerization. These findings highlight the potential of integrating bottom ash into fly ash-based geopolymers to enhance sustainability while maintaining adequate mechanical performance. The study also demonstrates that iso-conversional kinetic modeling provides a robust framework for understanding and optimizing geopolymerization processes.

Keywords: Bottom ash; CO2 emissions; Fly ash; Geopolymerization; Kinetics

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-05099-4

Chemical Papers 80 (10) 11875–11889 (2026)