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. 2025 Oct 2;15(1):34318.
doi: 10.1038/s41598-025-16574-5.

Geopolymerization of fly ash and GGBS for sustainable industrial waste utilization

Affiliations

Geopolymerization of fly ash and GGBS for sustainable industrial waste utilization

Ghausul Azam Ansari et al. Sci Rep. .

Abstract

This study aims to determine the feasibility of producing sustainable geopolymer bricks with industrial waste, such as fly ash and GGBS. The experimental investigations have been conducted at varying sodium hydroxide (NaOH) molarity (4 M, 6 M, 10 M, 12 M), GGBS incorporation levels (0%, 5%, 10%, 15%, 20%), curing temperatures (ambient, 60 °C, 80 °C, 120 °C), and curing durations (7, 14, and 28 days) to examine physical and mechanical properties of geopolymer bricks. The findings demonstrated a notable increase in compressive strength with elevated GGBS content, with a peak strength of 49.63 MPa at 20% GGBS, 10 M NaOH molarity, and a curing temperature of 80 °C after 28 days. Elevated curing temperatures improve the compressive strength, and attain its maximum value at 120 °C; however, 80 °C was identified as the optimal setting for balancing mechanical performance and energy efficiency. Moreover, the augmented quantity of GGBS enhanced bulk density and durability while reducing porosity and water absorption. In optimal conditions, microstructural analyses employing energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) revealed enhanced geopolymer gel development and a more compact matrix formation. Comparative analysis of SEM pictures and EDS data indicates that the high concentration of Ca and Si contributes to the dense microstructure and abundant C-S-H area. Geopolymer bricks exhibit enhanced strength owing to their significant C-S-H composition. The study concludes that the integration of industrial waste ashes, specifically with 10 M NaOH, 20% GGBS, and curing at 80 °C, yields high strength geopolymer bricks with enhanced microstructural properties, suggesting their viability as an environmentally sustainable substitute for conventional construction materials.

Keywords: Bulk density; Compressive strength; EDX; Fly ash; GGBS; Geopolymer; SEM; Water absorption.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests. Ethical approval: Not applicable.

Figures

Fig. 1
Fig. 1
Particle size distribution of the materials used in this study.
Fig. 2
Fig. 2
Flowchart cum experimental procedures to estimate different characteristics of prepare geopolymer bricks.
Fig. 3
Fig. 3
Variation in compressive strength (a) with the concentration of alkali activator (b) with curing temperature and (c) with different percentage of GGBS at curing period of 7 days.
Fig. 4
Fig. 4
Variation in compressive strength with different percentage of GGBS and curing temperature at (a) 14 days (b) 28 days.
Fig. 5
Fig. 5
Variation in compressive strength with curing period (a) at Room Temperature (b) 60 °C (c) 80 °C and (d) 120 °C, corresponding to 10 M solution.
Fig. 6
Fig. 6
Variation in bulk density with percentage GGBS at different concentration.
Fig. 7
Fig. 7
Variation in water absorption density with percentage GGBS at (a) 6 M (b) 10 M and (c) 12 M corresponding to different curing temperature.
Fig. 8
Fig. 8
SEM image and EDS spectrum of geopolymer brick at the end of 28 days consisting of (a) 70FA:30 S:0G (b) 65FA:30 S:5G (c) 60FA:30 S:10G (d) 55FA:30 S:15G (e) 50FA:30 S:20G.
Fig. 8
Fig. 8
SEM image and EDS spectrum of geopolymer brick at the end of 28 days consisting of (a) 70FA:30 S:0G (b) 65FA:30 S:5G (c) 60FA:30 S:10G (d) 55FA:30 S:15G (e) 50FA:30 S:20G.
Fig. 9
Fig. 9
SEM image and EDS spectrum of geopolymer brick at the end of 28 days consisting of 50FA:30 S:20G (a) 6 M and (b) 10 M.

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