Chapter 6 - Feasibility and performance evaluation of cementitious material mixed with coal gangue solid waste

Abstract

Coal gangue has become one of the largest solid waste in coal-producing countries. Seeking safe disposal and industrial utilization of coal gangue is an important research direction in the academic community. In this chapter, based on the alkali-activated method, preparation of coal gangue geopolymers and alkali-activated coal gangue-slag cementitious material with calcined coal gangue and slag as raw materials is discussed, and the feasibility of coal gangue as cementitious material instead of cement is comprehensively evaluated. The research results showed that coal gangue geopolymers can obtain high early strength, and the hydration products were N–A–S–H gel and other silico-aluminate zeolite phase crystals. The addition of slag can significantly improve the compressive strength of coal gangue geopolymers and produce flocculent C–(A)–S–H gels with high Ca/Si, Ca/Al, and Si/Al ratios, thus increasing the compactness of alkali-activated coal gangue-slag cementitious material. By adding a certain amount of slag as a calcium source, coal gangue can completely replace cement as cementitious material, and the 28-day compressive strength is higher than that of P.O 42.5 cement paste. This chapter provides a research basis for the use of recycled aggregates, reclaimed micropowders, tailing slag, and red mud as cementitious material.