석탄 경석 기반 LC3용 소성 점토의 반응성 향상에 관한 연구: 알루미나 공급원의 영향

초록

This study explores the feasibility of utilizing coal gangue as a calcined clay source for Limestone Calcined Clay limestone calcined clay cement (LC3) by examining its reactivity, hydration characteristics, and mechanical performance. Calcined gangue itself showed very low pozzolanic activity due to its high content of inert crystalline minerals, and the addition of reagent alumina offered limited benefits because the alumina was converted into non-reactive α-Al2O3 during calcination. In contrast, water treatment sludge used as an auxiliary alumina source produced amorphous Al–Si structures that substantially improved reactivity and promoted the formation of carboaluminate phases. Among all mixtures, the G-S25 blend demonstrated the most balanced hydration behavior and the highest 28-day strength, confirming its suitability for LC3 applications. Phase evolution analysis further revealed that sludge-derived alumina facilitated a smoother AFt to AFm transition and contributed to a denser, more cohesive micro-structure. The R3 test results also showed a clear increase in reactivity with higher sludge content, underscoring its effectiveness as a supplementary alumina source. Overall, combining coal gangue with water treatment sludge offers a practical strategy to overcome the limitations of low-reactivity clays, expands SCMs resource availability, and supports the development of low-carbon LC3 binders. This approach provides both an environmentally responsible recycling pathway and a meaningful contribution to CO2 reduction efforts in the cement industry.

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