Title : A practical approach to manufacturing sintered lightweight aggregates (LWA) from unrecycled coal combustion ash (CCA)
The focus of this study is to manufacture sintered lightweight aggregates (LWA) using unrecycled landfill condition coal combustion ash (CCA) that has been exposed to a harsh weathering and storage environment for 15-20 years. CCA under field conditions typically consists of an intricate blend of fly ash, bottom ash, boiler slag, flue gas desulfurization, cenosphere, sand, rocks, shells, twigs, and various land minerals. This complicated raw material blend obtained from a Pennsylvania landfill was characterized through various tests including moisture analysis, laser PSD, XRD, XRF, TGA, and SEM to understand its physical and chemical composition. A thermodynamics-based framework in conjunction with systematic laboratory experimentation were used to define the manufacturing processes required to achieve successful production of CCA-LWA. It was found that a lower bound viscosity of 100 Pa.s and a minimum of 35 % liquid phase content (% by mass) during sintering were necessary for manufacturing LWA with a standard traditional kiln (i.e., with temperature near 1100 °C). The CCA-LWA was assessed and classified in accordance with ASTM standards and is intended for geotechnical and concrete applications.