Towards sustainable geopolymers: Utilization of diverse calcined clays as alternative precursors

Geopolymers have emerged as a promising alternative to conventional cement-based materials due to their lower carbon emissions and alignment with sustainability goals. However, the limited availability of aluminosilicate sources remain a critical barrier to widespread adoption. This study investigates the potential use of calcined local clays as precursors for geopolymer production.Red, white, yellow, green, and black clay samples were characterized using X-ray diffraction (XRD), revealing the presence of illite, smectite, and kaolinite. The clays were then calcined at temperatures of 600-900 degrees C for 1, 2, and 3 hours, and their pozzolanic reactivity was evaluated via the Strength Activity Index (SAI) and rapid, relevant and reliable (R-3) test. Optimal calcination conditions were identified, and clays were further examined using XRD, X-ray fluorescence (XRF), and SEM-EDX techniques. Geopolymer pastes prepared with NaOH solutions of varying molarities (6-12 M) showed low early compressive strengths (<5 MPa). Improved performance was achieved using a NaOH/Na2SiO3 ratio of 1:1, with compressive strength increasing to 7.8-36.3 MPa at 7, 28, and 90 days. Additional FT-IR and SEM-EDX analyses provided insights into the reaction mechanisms. The study also explored the influence of SAI values, and iron content on geopolymer performance. The results confirm that calcined clays, when optimized, can serve as effective precursors in sustainable geopolymer production.

Journal

CONSTRUCTION AND BUILDING MATERIALS

Year

2025

Volume

484

ISSN

0950-0618

eISSN

1879-0526

DOI

10.1016/j.conbuildmat.2025.141785

WoS UID

WOS:001516181700012