水泥和粉煤灰及其硬化体中Cr(Ⅵ)的溶出行为

LEACHABILITY OF Cr(Ⅵ) IN CEMENT,FLY ASHES AND HARDENED FLY ASH CEMENT

调查分析了我国部分地区水泥、水泥熟料和粉煤灰,发现这些材料中均含有一定数量的可溶性六价铬离子Cr(Ⅵ)。研究了水泥、粉煤灰硬化体中Cr(Ⅵ)在标准溶出实验条件、酸性环境中以及碳化后的溶出行为,探讨了硬化体中Cr(Ⅵ)的溶出机理。结果表明:水泥水化产物对Cr(Ⅵ)具有很好的固化作用,但样品在受到碳化影响或在酸性环境条件下,Cr(Ⅵ)溶出量将明显增多。自水泥、粉煤灰硬化体中溶出的Cr(Ⅵ),除部分来自于孔溶液外,主要来自于硬化体本身各组分的溶出。

Cement clinkers and fly ashes produced in different areas of China were examined and leachable hexavalent chromium Cr（Ⅵ） was found in all samples. The leaching behavior and leaching mechanism of Cr（Ⅵ） in cement mortars and fly ash cement mortars were studied under different leaching conditions, i.e. standard leachability test （shaken extraction test） condition, acidic environment, as well as being carbonated. The results show that the leaching of Cr（Ⅵ） is greatly reduced after hydration of cement. However, the leaching of Cr（Ⅵ） increases remarkably in acidic environment or when carbonation occurs in cement mortars. The shaken extraction tests of hardened cement pastes and mortars reveal that the majority of the leached Cr（Ⅵ） is from cement hydrates, fly ash and unhydrated cement particles, while only a small amount of leached Cr（Ⅵ） is from the pore solution.