Abstract
Making of sewage sludge-derived controlled low-strength materials (CLSMs) is an alternative option for sludge disposal. Reuse of dewatered sludge (DS) and municipal solid-waste incineration bottom ash (MSWI BA) as starting materials in producing CLSM is possible. It is found that the strength of tested CLSM mixtures ranges from 3.6 to 9.0MPa after 28days, and roughly 2.0–6.2MPa after 1year of curing, over the upper excavatable limit of 2.1MPa. The microstructural analysis reveals that ettringite (AFt,C3A·3CS¯·H32) crystals are the most important strength-producing constituent. The addition of BA favors the formation of highly crystalline AFt phases via the typical pozzolanic reaction. Sludge and BA are crystallochemically incorporated within CLSM systems by forming the needle-like AFt with exiguous tubers, which diminishes the porosity of system and enhances the compressive strength of CLSM. Leaching tests evidence that leachable substances in the leachate are comparatively low, exhibiting negligible health and environmental risks. This recovery technology of utilizing sludge and MSWI BA can produce high-performance CLSM thus reducing costs, in accordance with the concept of sustainable development.
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