用Pb(Ⅱ)参与钙矾石的合成试验表明,在SO42-存在时,钙矾石把少量的Pb(Ⅱ)包容在其晶格内,造成化学俘获,但在无SO42-时,Pb(OH)3-不能替代SO42-进入钙矾石晶格;另一种水泥水化物CSH在碱性条件下对溶解态Pb(Ⅱ)的吸附很强.监测水泥浆液中溶解态Pb(Ⅱ)、SO42-的浓度和pH值的变化过程可知,PbSO4和Pb(OH)2的沉淀作用能把绝大多数的溶解态Pb(Ⅱ)予以固化.采用TCLP检测法检测表明,采用复合型水泥固化Pb2+的效果良好,尤其是不掺石膏的复合水泥.虽然搅拌水中Pb2+的浓度达到4g/L,但其28d龄期的胶砂粉碎样滤取Pb2+的浓度已低至0.0002g/L.由于形成的Pb(OH)2沉淀物阻止水泥水化使得掺Pb(NO3)2后砂浆试件早期的抗压强度有所降低.因此,复合水泥对铅固化的机理主要是Pb(Ⅱ)在水泥浆中发生的沉淀作用、水化物对Pb(Ⅱ)的化学俘获和混凝土中微孔隙对含Pb微粒的裹限作用.
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