Reuse of incineration fly ashes and reaction ashes for manufacturing lightweight aggregate

This paper reports the result of the investigation on manufacturing lightweight aggregate by incorporating municipal solid waste (MSW) incineration fly ashes and reaction ashes with reservoir sediments. The investigation was first performed in a laboratory scale to assess the effects of the composition and the firing conditions on the properties of the resulting aggregate. Afterward, a big amount of aggregates was manufactured in a pilot scale using a commercially available rotary kiln. Physical properties of the synthetic aggregates were subsequently assessed. In addition, compressive strength of the concrete made from the manufactured aggregates was experimentally measured. The investigation shows that the analysis results for the MSW incineration fly ashes and reaction ashes are not in the limits of the expandable region of Riley’s ternary diagram due to the low content of SiO2. Therefore, they can only be used as additives. The proper content for MSW incineration ashes should not exceed 30%, except compositional adjustment using oxide constituents. The particle density of the manufactured aggregates using a commercially available rotary kiln was 0.99 g/cm3, which is significantly lower than normal density aggregate. Moreover, its dry loose bulk density is 593 kg/m3, which meets the requirements of ASTM C 330 with bulk density less than 880 kg/m3 for coarse aggregate. On the other hand, the results of toxicity test meet the Taiwan Environmental Regulatory requirements, which demonstrate that the aggregate thus fabricated is non-hazardous for construction use.