Make full using coal chemical solid waste to prepare coal goaf filling concrete and its structure and properties

The environmental problems caused by coal goaf collapse and coal chemical solid waste pollution urgently need to be solved in China. This paper introduces the solution of technical problems encountered in preparing goaf filling materials from coal chemical solid waste to solve their environmental problems. An adhesive curing agent (ACA) for solid waste surface coating was prepared by free-polymerization of acrylic acid, 2-vinyl-4,6-diamino -1,3,5-triazine and hydroxyethyl acrylate. Then it was mixed into cement paste containing graphene oxide (GO) for surface coating of the coal chemical solid waste. The main influencing factors of the concrete strength were studied by analysis of variance (ANOVA). The test results indicated the surface morphology, internal microstructure, water absorption, bulk density and porosity of treated solid waste have met the requirements of replacing gravel in preparing goaf filling concrete. The microstructure show that the concrete contained GO has dense and uniform structures compared with the control samples. The strength results indicated that this technology can increase the solid waste content in goaf filling concrete, C30 and C40 strength grade building concrete to 80%, 66% and 51%, respectively. The results of dry shrinkage and durability also show that the solid waste concrete containing GO has little dry shrinkage value and good durability. This technology can maximize the use of solid waste of coal chemical industry to prepare goaf filling and construction concrete, and has significant economic and environmental benefits. Therefore, the technology can minimize the environmental problems caused by goaf and solid waste of coal chemical industry. The application of the results of this study will produce a huge circular economy and ecological environment effect.