Co-sintering oyster shell with hazardous steel fly ash and harbor sediment into construction materials

Oyster shell is used to partially replace steel fly ash in the mixture of harbor sediment and steel fly ash for preparing lightweight aggregates, aiming to both prepare LWAs at temperatures lower than what usually employed and solve the disposal problem of oyster shell. The replacement percentages are 5%, 10%, and 15%. The mixtures are pressurized into pellets and sintered at 1050-1130 °C/1150 °C for 10 min. Heavy metal leaching from the sintered pellets is dramatically reduced as compared to raw materials. Leaching results of toxic metals, including Cd, Se, Cr, Pb, As, Ag, Cu, and Ba, well meet government's environmental legal limits. An increase in sintering temperature from 1000 °C to 1130 °C/1150 °C always reduces the leaching level. Sintered at ≥1050 °C, all pellet particle densities, except the one not containing oyster shell sintered at 1050 °C, meet the practical particle density requirement as lightweight aggregate, <1.6 g/cm3, for construction sector. Oyster shell amendment generally results in lower particle density with the 5% amendment resulting in the least particle density. Over-replacement of steel fly ash with oyster shell leads to an increase in particle density due to partial melting. Moreover, 24-h water sorption rate of all lightweight aggregates also meets the requirement abided by practical construction sector, <18-20%.