Preparation and characterization of green lignin modified mineral cementitious firefighting materials based on uncalcined coal gangue and coal fly ash

In this study, lignin modified cementitious materials (LFGS) were synthesized to determine the viability of mineral cementitious sealing and firefighting materials using uncalcined coal gangue (UCG) and fly ash (FA) as raw materials in order to realize the resource utilization of coal-based solid waste and prevent spontaneous combustion of coal gangue and coal fires. The 28-d compressive strength was increased to 63 MPa, the fluidity was improved to 142 mm, and the final setting time was shortened to 75 min with 0.1 wt% lignin. Thermal exposure experiments demonstrated that lignin modification could improve the high temperature resistance in terms of residual compressive strength , thermal crack and shrinkage resistance. The microstructure and thermogravimetric characterization of the resulting cementitious materials revealed the generation of a dual-crosslinked network composed of covalent linkages (Si-O-Al bonds) and hydroxyl groups-Ca 2+ coordination bonds. The average air sealing efficiency of LFGS was found to be 53.7% higher than that of ordinary Portland cement slurry. The examination of the CO 2 emissions of the cementitious materials revealed that the carbon emission index of LFGS was approximately 55% lower than that of ordinary Portland cement . This study not only presents a resource utilization strategy for uncalcined coal gangue and coal fly ash, but also a green and low carbon emission cementitious firefighting material to prevent coal fires.