Study on the Setting Characteristics, Mechanical Properties, and Volumetric Stability of Alkali-Activated Metakaolin-Based Composite Materials

Abstract:

Traditional Portland cement production generates substantial CO₂ emissions, hindering sustainable low-carbon building materials. This study develops a cement-free alkali-activated geopolymer using metakaolin as the primary binder, blended with 0%, 10%, and 20% ground granulated blast-furnace slag (GGBFS) by weight, activated by sodium hydroxide and sodium silicate. It examines physical properties, including setting time, compressive strength, and volumetric stability, under varying GGBFS levels, with chemical analysis via FTIR and DTG. Increasing GGBFS accelerates polymerization, reducing initial setting time from 4 hours (0% GGBFS) to 2 hours (20% GGBFS), with final setting time similar. Compressive strengths (MPa) under ambient curing at 1, 7, and 28 days for M100S0, M90S10, and M80S20 are 8.34/13.34/26.28 at 1 day, 31.77/45.90/45.68 at 7 days, and 34.8/45.4/42.1 at 28 days. Early-age strength improves with higher GGBFS due to additional calcium facilitating C-S-H gel formation, while strengths stabilize beyond 28 days. Volumetric stability shows no significant shrinkage or expansion within three days across mixtures, with maximum strain below 0.12%, indicating excellent stability. FTIR shows enhanced Si-O-Al bond intensity (~1050 cm⁻¹) in GGBFS samples, reflecting greater Al incorporation into silicate tetrahedra and denser amorphous structure. The O-H stretching peak (~3400 cm⁻¹) narrows slightly, signifying reduced water and improved polymerization. DTG corroborates enhanced polymerization efficiency with GGBFS. These results highlight superior mechanical properties and stability of GGBFS-blended metakaolin geopolymers, positioning them as promising for subgrade soil stabilization, improving early bearing capacity and long-term durability for sustainable construction.

• Periodical: Advances in Science and Technology (Volume 179)
• Pages: 3-8
• DOI: https://doi.org/10.4028/p-d6GvAX
• Online since: June 2026
• Authors: An Cheng, Pin Chien Cheng*, Qi Zhen Huang, Yuan Ho Cheng, Kai En Lan, Hui Mi Hsu
• Keywords: Alkali-Activated Geopolymer, Blast Furnace Slag, Low-Carbon Emission, Metakaolin, Microstructural Analysis

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