Application of Coal Gangue as a Coarse Aggregate in Green Concrete Production: A Review

Shan Gao,Sumei Zhang,Lanhui Guo

doi:10.3390/ma14226803

Abstract

Among the techniques for converting stacked coal gangue to reusable material, one of the most effective ways is to use coal gangue as a coarse aggregate in green concrete productions. The physical and chemical properties of rock and spontaneous-combustion coal gangue are generally suitable for being used as a coarse aggregate in green concrete. Coal gangue concrete is not recommended to be used in subsurface structures, as its water absorption law would be changed under a large replacement ratio. The mechanical performance of coal gangue concrete is degraded by raising the replacement ratio. Over-low and -high concrete grades are not suggested to be used as coal gangue aggregate, unless extra admixtures or specific methods are used. The influence of coal gangue on the durability of coal gangue concrete is remarkable, resulting from the porous structure of coal gangue that provides more transmission channels for air and liquid in concrete, but is beneficial for thermal insulation. The usage of coal gangue in structural concrete members is still limited. The mechanical behavior of some structural members using coal gangue concrete has been reported. Among them, concrete filled steel tubes are a preferable configuration for using coal gangue concrete, regarding both the mechanical and durability performance.

Highlights

Even though many kinds of new energy and renewable fuels have been explored nowadays, coal is still the main energy for many countries in the world, especially for countries in Asia Pacific region, such as China, Indonesia, and Vietnam
More specific permission regarding heavy metal and organic matter leaching in coal gangue should be issued by governments to avoid posing environmental, health, and safety concerns
A proper index to assess the workability of coal gangue concrete for practical use should be proposed based on more experimental data

Summary

Introduction

Even though many kinds of new energy and renewable fuels have been explored nowadays, coal is still the main energy for many countries in the world, especially for countries in Asia Pacific region, such as China, Indonesia, and Vietnam. Coal still accounts for more than 70% of energy expenditure in China [2], while the world coal expenditure fell to its lowest level in 16 years, as a result of being displaced by natural gas and renewables. Normal disordered gangue stacking tends to result in debris flow [2,4,5]. It is well-known that the composition of coal gangue changes along with storage time and environment [7]. The heat continuously accumulating inside the stocked coal gangue leads to the spontaneous combustion of coal gangue in the form of fire, even blast disasters, due to the existence of unburned coal, pyrite, and oxygen, releasing a large amount of harmful gases, including SO2, NOx, and CO, into the atmosphere. It is a pity that this air pollution from coal gangue is hard to control [2,4]

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Conclusion