利用电子探针对水泥净浆中Cr、As、Pb分布特征的研究

Distribution of Cr,As and Pb in cement mortar determined by electron probe microanalysis

通过在模拟水泥窑中高温煅烧含Cr、As、Pb的水泥生料,制取水泥熟料,进而制备水泥净浆片.然后利用电子探针的点、线、面分析,研究了水泥净浆中Cr、As、Pb的整体分布特征及在不同矿物相中的具体分布特征,以揭示Cr、As、Pb在其中的微观物理化学形态,为建立Cr、As、Pb的释放机制提供理论基础.结果表明,Cr在水化硅酸钙凝胶中存在富集现象,含量自凝胶中心向外递减,在水化氢氧化钙晶体、中间相等矿物相中的含量较低,此外,还存在部分富Cr颗粒.各矿物相中,仅水化硅酸钙凝胶中分布有As,其它相中As含量几乎为零,大部分As可能形成砷酸盐物理附着或吸附于各水化产物表面.Pb的分布较为分散,各矿物相中Pb含量均维持在较低水平,在水化硅酸钙凝胶中的含量稍高,大部分Pb可能与其它元素形成某些化合物散布于水化产物表面.

Clinker and cement mortar were produced from raw materials with Cr,As and Pb by simulating the high-temperature calcination in a cement kiln.According to the electron probe microanalysis （EPMA） point,line and surface analysis,the distribution and mineral phases of Cr,As and Pb in cement paste and concrete were identified and the microphysicochemical species of Cr,As and Pb were characterized,thus establishing a theoretical basis to understand the release mechanisms of Cr,As and Pb in cement paste.The results show that：Cr was predominantly enriched in the calcium silicate hydrates,whose content decreases gradually from the center of the gel to the circumference.Other mineral phases,including portlandite crystal and middle phases,with lower content,and some Cr grains with high concentration of Cr exist in the gel.In the cement mortar,only the calcium silicate hydrates contained As,the content in other mineral phases being nearly zero,and the majority of As is likely to form arsenate on the surface of hydration products in the form of physical fixation or sorption.The distribution of Pb in the cement mortar was highly decentralized.A low level of Pb was present in every hydration product,the calcium silicate hydrates being an exception with a somewhat higher Pb content.A large portion of Pb probably forms some compounds with other elements dispersed on the surface of each hydration product.