Mine Tailings and Bottom Ash from Waste Incineration as Alternative Fine Aggregates for Controlled Low-Strength Materials

Abstract

Solid waste generation and its sustainable disposal are big concerns in the present decade. Mine tailings and incinerated bottom ash are among the greatest solid waste contributors to the environment. To promote sustainable development, material reuse and recycling are important. In the present study, a feasibility study was conducted by utilizing such tailings and bottom ash for the production of controlled low-strength material (CLSM). The amount of cement was utilized less, and by controlling the design mix with a targeted flow, low-strength material was produced. Three different cement contents (60, 80, and 100 kg/m3) and 100% mine tailings or incinerated bottom ash were used as fine aggregate material. Fresh properties of different CLSM mixes, mechanical performance, and leaching behavior were conducted to confirm the final product. It was observed that both the mine tailings and bottom ashes are suitable as an aggregate material for CLSM mixes. The compressive strength values of different CLSM mixes at 28 days were observed between 0.13 and 1.88 MPa for various aggregate materials (mine tailings and bottom ash) and cement content. Moreover, there is an influence in the reactivity of cement hydration by the aggregate (tailings and ash), which was confirmed by the calorimetry study. The selected mine tailings and bottom ashes are not inert (like natural aggregate) within the CLSM mixes, and the chemical composition of the raw materials affects their fresh and hardened properties. The leaching test further shows that the final product could leach different heavy metals beyond the limit for inert materials, but within the nonhazardous limits by international standards. The present work deals with CLSM mixes with locally available industrial side streams; some important properties such as hardening time, penetration resistance, shrinkage, excavatability, and other durability properties (i.e., acid attack, freezing and thawing resistance) were not considered in the study and can be studied further.