INCORPORATION OF BOTTOM ASH FROM MUNICIPAL SOLID WASTE INCINERATOR INTO PERVIOUS CONCRETE: A SUSTAINABLE APPROACH

Abstract

Amounts of generated municipal solid wastes (MSW) are augmented by the fast population growth and development, making MSW management a great challenge for countries worldwide. Although landfilling is a convenient waste disposal approach, it has hazardous environmental, health, social, and economic effects directing countries to shift towards other waste management approaches. With the advantage of reducing the volume of waste and recovering energy, MSW incineration process is being adopted by various countries. Given that Lebanon is a small country, experiencing waste management challenges, incineration of MSW might offer a solution. Incineration of MSW is the conversion of wastes into flue gas, ash, and heat. Environmental concerns of the incineration process can be addressed by controlling the emissions of hazardous flue gases, and managing the residues (fly and bottom ash). Among the incineration byproducts, bottom ash (BA) constitutes 80-90% of the total ash content. Thus, sustainably dealing with the produced bottom ash is a priority.

The construction industry is facing challenges stemming from overexploitation and, hence, depletion of natural materials. Therefore current global trends are focused on exploring new sustainable recycled materials as alternatives for construction raw materials. This is applicable for all types of concrete structures (conventional concrete, pervious concrete, etc.) in various applications (buildings, bridges, roads, etc.).

Pervious concretes containing 5%, 10%, 20%, and 30% replacement of aggregates with bottom ash were prepared and tested for their air voids content and compressive strength. After validating the viability of bottom ash incorporation into pervious concrete, possible leachability of selected heavy metals from bottom ash - under neutral and acidic water - was investigated.

Results showed that pervious concrete containing 5 up to 20% bottom ash replacement achieved a relatively adequate compressive strength for pervious concrete exceeding 14 MPa. However, the compressive strength dropped when bottom ash content surpassed 20%. As for the leachability of heavy metals, results indicated that the concentrations of heavy metals in all tested water samples are below the allowable limit in waste as set by the Environmental Protection Agency (EPA). The obtained results suggest that bottom ash, as a substitute of aggregate, is environmentally safe.