飞灰固化工程材料在碳化条件下的强度及环境特性研究

螯合剂常用于固定重金属污染物,水泥可有效提升材料的强度,而碳化效应对水泥基材料工作性能有着显著影响。因此,采用水泥和螯合剂对固体废弃物焚烧飞灰进行协同处理制备固化飞灰复合工程材料,并探究碳化效应对其强度及环境友好性的影响。结果表明,常规养护28 d的飞灰复合材料强度达到3~6 MPa,高达规范中水泥土强度标准的7.5倍,且其强度随着龄期及水泥掺量的增加而增大,而碳化效应可有效的提升材料的强度特性;经处理后的飞灰复合材料中重金属Cd、Pb、Ni和Cr的浸出分别仅为原灰的2.0%,1.0%,19.2%和14.1%,碳化试样浸出略高,但仍满足固废浸出标准;碳化深度随养护龄期的增加而增大,与水泥掺量呈反比。优良的工作性能和环境友好性使材料在建设工程领域展示出极大的资源化利用潜力和价值。

Strength and environmental behaviors of solidified fly ash under carbonation effect

The cemented solidification/stabilization has been widely adopted for fly ash around the world, since it can effectively enhance strength and restrict heavy metals. However, the carbonation effect has a significant impact on the performance of cement-based materials. Thus, the carbonation on strength characteristics and heavy metal toxicity of samples solidified with cement and chelating agent is evaluated. The test results show that the strength of samples after 28 d of standard curing has reached 3~6 MPa, which is 7.5 times more than that of cement soil. Besides, the carbonated specimens with chelating agent of 6% show the highest strength is more than those with 3% and 9%. Considering the leachability of heavy metals, the leaching concentration of Cd, Pb, Ni and Cr of cement-chelated solidified fly ash is only 2.0%, 1.0%, 19.2% and 14.1% of raw fly ash, respectively. Compared with the samples cured under standard condition, the carbonated specimens show higher leachability. Both of them reach the leaching standards and are environment-friendly. Furthermore, the carbonation depth increases with the curing time and is inversely proportional to the cement content.