An experimental study on the mechanical properties of underground mining backfill materials obtained from recycling of construction and demolition waste

Environmental and safety factors have caused the mining industry to consider backfilling underground openings to prevent mine collapse in deeper and further extraction operations. This paper discusses the possibility of utilizing the construction and demolition waste (CDW) as cemented recycled aggregate backfill (CRAB) materials in the underground mining industry. In this regard, several samples were prepared by mixing the recycled aggregates of CDW components and Portland cement and various tests were performed to consider their physical and mechanical properties. Results indicate that by adding 8% cement content to the mixture, the uniaxial compressive strength (UCS), the most important property of backfill materials, reaches 4.95 MPa. Based on common compressive strength criteria of backfill materials, the obtained value of UCS satisfies the prerequisite for most underground mining applications. There are situations, such as the ground support, where higher UCS quantities are required for backfill materials. By removing the plaster and soil components of CDW from the mixtures, the compressive strength of samples has increased by 55.4% and 7.1% respectively. Therefore, by removing the plaster from the mixture, the prepared samples meet the requirements of ground support applications. Moreover, with the increase in cement dosage, the effects of cement content on the properties of the CRAB samples were investigated.