Recycling of municipal solid waste incineration ash as raw material in cold-bonded lightweight aggregate

This study focusses on the development of new lightweight aggregate (LWA) that eventually have comparable properties with existing natural aggregate which is granite. The main objective of this study is to examine potential use of recycled municipal solid waste incineration (MSWI) ash as raw material in LWA production with a method of cold-bonded pelletization process. The ashes are collected from Cameron Highland Incineration Plant, Malaysia that can be divided into bottom ash (BA) and fly ash (FA). The properties of BA and FA are studied by means of X-Ray Fluorescence (XRF), Scanning Electron Microscope (SEM) and apparent density test. The LWA is denoted as bottom ash lightweight aggregate (BALA) and fly ash lightweight aggregate (FALA). Both BALA and FALA have experienced two different curing process for 28 days namely room-room (RR) and room-water (RW) curing conditions. The percentage of BA and FA used in this study were 10 %, 20 %, 30 %, 40 % and 50 % of partial cement replacement and the size of aggregate is fixed between 10 mm to 20 mm with circular shape. The properties of BALA and FALA produced in this study is examined including loose bulk density, water absorption, aggregate impact value (AIV) and specific gravity. Other physical properties including colour and texture are also being investigated. Potential use of BALA and FALA in concrete is investigated by selecting optimum samples of both aggregates to be incorporated in the manufacturing of semi-lightweight aggregate concrete (SLWAC). 30 specimens of SLWAC were produced having water-cement ratio of 0.5 and percentage of aggregate replacement is fixed at 20 %. Characteristics of SLWAC were examined including workability, density, water absorption, capillary water sorption, ultra-pulse velocity (UPV), compressive strength and permeability. Distribution of BALA and FALA in SLWAC is examined through cut-section of concrete. From the results of LWA it is clearly seen that 20 % BA and 20 % FA were the best percentage of ash used to produce good quality LWA. Loose bulk density of BALA selected is 739.53 kg/m3 with water absorption 20 % and AIV 13.94 %. Meanwhile, for FALA, optimum percentage is as follows; loose bulk density 716.72 kg/m3, water absorption is 19.7 %, AIV 13.80 % and specific gravity 1.670. However, for SLWAC, the results show that by incorporating BALA and FALA in the concrete improved the workability of concrete. The obvious impact due to the reduction of loose bulk density in LWA can be evident by the reduction of apparent density of SLWAC. Compressive strength of FASLWAC is comparable with NWC. Well-distributed BALA and FALA in concrete specimens is believed to contribute to the properties of SLWAC.