硫酸亚铁替代石膏对水泥中Cr(Ⅵ)降低和水泥性能的影响

Effect of replacing gypsum by ferrous sulfate on Cr(VI)reduction in cement and cement properties

硫酸亚铁在水泥中还原六价铬Cr(Ⅵ)时,其用量较高会增加水泥中SO 3的含量,并且会降低水泥的抗压强度等性能。因硫酸亚铁与石膏都属于硫酸盐,具有相似性,且可延长水泥的凝结时间,故可用硫酸亚铁部分替代水泥中的石膏,研究硫酸亚铁替代石膏后对水泥中Cr(Ⅵ)含量和水泥净浆中Cr(Ⅵ)溶出量的影响,并研究了硫酸亚铁替代石膏后对水泥凝结时间、抗压强度和水化产物等性能的影响。结果表明:当硫酸亚铁替代0.3%的石膏时,Cr(Ⅵ)含量从11.8 mg/kg降到2 mg/kg以下且不会降低水泥28 d的抗压强度,硫酸亚铁替代石膏后会促进钙矾石的形成,延长水泥净浆的凝结时间;当硫酸亚铁替代量小于1.0%时会促进水泥的水化;硫酸亚铁替代石膏后会降低水泥净浆中水溶性Cr(Ⅵ)的溶出,且28 d时水溶性Cr(Ⅵ)的溶出量为0。

When ferrous sulfate is used to reduce hexavalent chromium Cr(Ⅵ)in cement,its high dosage will increase the content of SO 3 in cement and reduce the compressive strength of cement.Because ferrous sulfate and gypsum all belong to sulfate,and they are similar to each other in properties and can prolong the setting time of cement,ferrous sulfate can be used to partially replace gypsum in cement.The effects of replacing gypsum by ferrous sulfate on the content of Cr(Ⅵ)in cement and the dissolution of Cr(Ⅵ)in cement paste were studied.In addition,the effects of replacing gypsum by ferrous sulfate on the setting time,compressive strength and hydration products of cement were studied as well.The results show that when 0.3% gypsum is replaced by ferrous sulfate,the content of Cr(Ⅵ)decreases from 11.8 mg/kg to less than 2 mg/kg without reducing the compressive strength of cement at 28 d.The replacement of gypsum by ferrous sulfate will promote the formation of ettringite and prolong the setting time of cement paste.When the replacement amount by ferrous sulfate is less than 1.0%,it will promote the hydration of cement.The replacement of gypsum by ferrous sulfate will reduce the dissolution of water-soluble Cr(Ⅵ)in cement paste,and the dissolution of water-soluble Cr(Ⅵ)is 0 at 28 d.