Physico-Mechanical Characterization of Kazakhstan Diatomite–Opacifier Geopolymers under Electrothermal and Conventional Curing

Bolat Balapanov; Sarsenbek Montayev; Orhan Canpolat; Beyza Aygun; Mucteba Uysal

doi:10.48084/etasr.12056

Authors

Bolat Balapanov Department of Architecture and Construction, Institute of Engineering and Technology, Korkyt Ata Kyzylorda University, Aitekebi 29A, Kyzylorda, Kazakhstan
Sarsenbek Montayev Industrial Technological Institute, Zhangir Khan West Kazakhstan Agrarian and Technical University, Uralsk, Kazakhstan
Orhan Canpolat Department of Civil Engineering, Faculty of Civil Engineering, Yildiz Technical University, Istanbul, Turkiye
Beyza Aygun Istanbul Okan University, Vocational School Construction Technology Program, Turkiye
Mucteba Uysal Department of Civil Engineering, Faculty of Civil Engineering, Yildiz Technical University, Istanbul, Turkiye

Volume: 16 | Issue: 1 | Pages: 32240-32259 | February 2026 | https://doi.org/10.48084/etasr.12056

Received: 11 May 2025 | Revised: 10 June 2025, 30 June 2025, and 7 July 2025 | Accepted: 9 July 2025 | Online: 9 February 2026

Corresponding author: Beyza Aygun

Abstract

Focusing on sustainable construction materials, this study investigates the development of Geopolymer Composites (GCs) using Kazakhstan's abundant industrial by-products, including Fly Ash (FA), Slag (S), Diatomite (D), and Opacifier waste (OP). All precursors were sieved to below 90 µm to improve homogeneity and reactivity, and a 2:1 mass fraction binary alkali activator comprising 12M NaOH and Na₂SiO₃ was used at an Activator/Binder (A/B) ratio of 0.7, resulting in an Ms value of 3.29 and an estimated value for the water/binder ratio of about 0.28. Seven different GCs, ranging from single-phase mixtures containing only D and opaque to ternary combinations, were prepared and subjected to three curing regimes: ambient (23 ± 2 °C, 95% RH), thermal (80 °C for 24 h), and electrical curing (30-50V for 1-24 h). Compressive and flexural strength, capillarity, water absorption, and microstructural properties were evaluated. Electrical curing at 40 V in the 50S25FA25D series did not improve compressive strength compared with thermal curing at 80 °C; however, it improved flexural strength by approximately 13.5%, outperforming thermal curing and indicating enhanced tensile stress distribution and internal gel continuity. Although apparent porosity slightly increased by 2-3% and water absorption was 5-12% higher under electrical curing, these values remained within acceptable ranges. They were compensated by more uniform heat distribution and reduced the risk of thermal gradient cracking. The energy consumption required for electrical curing was more than 60% lower than thermal curing, making it significantly more sustainable and operationally more efficient.

Keywords:

geopolymer, diatomite, opacifier waste, electrical curing, physico-mechanical properties

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