Synergistic performance of microwave-activated coal gangue with limestone in low-carbon cement

This study aims to apply microwave-activated coal gangue (MCG) to develop limestone calcined clay cement (LC3). The impact of microwave activation schemes (microwave temperature and holding time) on the pozzolanic activity of coal gangue were explored. After that, LC3 cements were prepared by replacing cement clinker with limestone powder (LS) and MCG at different ratios. The uniaxial compressive strength, phase composition, microstructure, and pore structure of the MCG-based LC3 cements were analyzed. The results indicate that the maximum volcanic ash activity index is achieved when the material is microwave-activated at 800°C with a holding time of 20 minutes. The MCG based LC3 cements achieve the highest strength at an MCG content of 20% with an MCG:LS ratio of 2. Then, the response surface methodology was employed to predict the optimal mixture proportions for achieving the best strength of the material. The life cycle analysis shows that the carbon emission of the MCG-based LC3 material is 30% lower than that of ordinary Portland Cement. This study develops a new high-performance material with low carbon emission for construction industry.