垃圾焚烧飞灰胶凝活性和水泥对其固化效果的研究

CEMENTITIOUS REACTIVITY OF MUNICIPAL SOLID WASTE INCINERATION FLY ASH AND IMMOBILIZATION EFFECT BY CEMENT

垃圾焚烧飞灰是生活垃圾焚烧后烟气除尘器收下的物质,其主要成分属CaO-SiO_2-Al_2O_3-Fe_2O体系,与目前常用的高炉矿渣、粉煤灰等辅助性胶凝材料非常接近,因其中含有能被水浸出的重金属物质而被认为是危险废物,必须对之进行稳定及固化处理。通过试验研究了掺入垃圾焚烧飞灰的硬化水泥浆体的力学性能和水化机理,考察了水泥固化垃圾焚烧飞灰的效果,探讨了垃圾焚烧飞灰作为辅助性胶凝材料利用的可行性。研究表明:垃圾焚烧飞灰的水化反应活性较低,它的掺入在一定程度上延缓了水泥的水化过程,虽然其水化过程可以形成适量的钙矾石,对强度发展有利,但掺量较大时会显著降低水泥强度;采用水泥稳定及固化垃圾焚烧飞灰的效果良好,垃圾焚烧飞灰中重金属可以通过包容、替代或吸收等形式固化进水化产物结构中。

Municipal Solid Waste Incineration(MSWI) fly ash is from scrubber after incineration of municipal solid wastes, its main composition is CaO, SiO2 , Al2O3 , and Fe2O3 , similar to the blastfurnace slag and the fly ash produced by burning pul-verized coal in power stations. MSWI fly ash contains some heavy metals, which can be leached by water, so it is regarded as hazardous matter, and must be solidified/stabilized. The mechanical properties and hydration mechanism of the hardened ce-ment paste containing MSWI fly ash were studied. The effect of immobilization of cement on MSWI fly ash was investigated. And the feasibility of MSWI fly ash as auxiliary cementitious materials was indicated. The results show that the reactivity of MSWI fly ash is lower and its addition to cement causes retardation of cement hydration, the formation of ettringite during the hydration process is beneficial to enhancement the strength, but a large amount of addition of MSWI fly ash will cause the de-crease of the strength of the hardened cement paste. It is efficient to use cement for immobilization MSWI fly ash. The heavy metals can be immobilized in the structure of the hydration phases by holding, substitution or sorption.