۱- Introduction

۲- The role of waste materials recycling in sustainable development

۳- Materials

۴- Experimental work

۵- Results and discussion

۶- Conclusions

References

Abstract

Recently, researchers have tried to find ways to reduce the negative effects of untreated coal wastes (UCW) on the ecosystem of the region. Recycling untreated coal wastes can however be identified as a practical solution in producing concrete aggregates. The present study investigates the mechanical properties of green concrete having untreated coal wastes. A total of eleven mix designs with different contents of untreated coal waste as aggregates were prepared and the cube, cylinder and prism compressive, tensile and flexural strengths as well as the elastic modulus of specimens were determined. The results revealed that untreated coal waste particles can potentially be reused in manufacturing concrete aggregates. It was also confirmed that selecting an appropriate amount of replacement can contribute to the property improvement of concrete, also suggesting an environmental solution to reducing untreated coal wastes. Therefore, replacing 5% of the aggregate with untreated coal wastes instead of sand and gravel, the mechanical properties increased. On average, in sand and gravel replacement compressive and flexural strength increased about 3–۷% and 5–۸%, respectively.

Introduction 

As industry and technology are developing and human population is growing, global solid waste generation is accelerating. Generally, there are three methods of disposing such materials, i.e. burial, incinerate and recycling [1]. A number of studies have considered the feasibility of utilizing recycled waste materials in the civil engineering discipline [3–۷]. Untreated coal is regarded as a significant source of energy on earth and is widely used in various practices. However, coal extraction results in generation of waste material which is not treated because of its high economic costs. Specific regulations have already been set on the efficient reuse of waste materials and by-products via some of the societies, so as to conserve natural resources [8]. Waste material is any kind of byproducts generated by human or industrial activity without any lasting value [9]. Various types of waste materials have been utilized as secondary construction materials. Due to the high potential of waste materials for producing environmental pollution, issues related to isolation and monitoring measures have been addressed [10]. Several investigations have cited the benefits of coal combustion products in highway construction in the U.S. Nevertheless, findings have not proved that these products may jeopardize human health or significantly pose a risk to the environment [11]. Thanaya [12], studying the consequences of coal ash on the hot and cold mix asphalts, noticed the merits of incorporating coal ash in both cold and hot mix asphalts as a filler material. They asserted that hot and cold blends, mixed with coal ash, can be implemented in districts with low to medium traffic densities and the sidewalks. Verma [13] examined the viability of using waste material byproducts in making ash bricks. They stated that the prism strength of coal ash masonry bricks is higher respecting the conventional ones.