An X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) characterization of the speciation of arsenic (V) in Portland cement type-V

The speciation of As(V) bearing oxyanions (AsO43−) in cementitious environment has been investigated by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). The hydration of Portland cement type-V(OPC-V) was found to be retarded in presence of AsO43−, and the retardation was caused mainly by the formation of highly insoluble calcium arsenate on the surface of hydrating cement particles. Arsenate substituted analog of ettringite (Ca6(Al2O6)(SO4)3·32H2O, was also identified by XRD analyses of the samples. Examination of the FT-IR spectra of AsO43− treated cement indicated interactions of the oxyanions with cement particles. The `Charge Dispersed Modelʹ has been used to elucidate the mechanism of speciation of As(V) in cement.