An NMR and XRD study of solidification/stabilization of chromium with Portland cement and β-C_2S

摘要

Solidification/stabilization of chromium with Portland cement Type Ⅰ and β-dicalcium silicate (β-C_2S) was investigated by means of the ~(29)Si solid state Magic Angle Spinning/Nuclear Magnetic Resonance (~(29)Si MAS/NMR) and X-ray Diffraction (XRD) techniques. It is found that chromium nitrate can increase the extent of β-C_2S hydration. It is also confirmed that the chromium ion is easily incorporated into the β-C_2S paste and hydrated Portland cement, and that it affects the characteristics of hydration and hydration products. Formation of β-calcium chromium oxide hydrate (β-CaCrO_4·2H_2O) during the hydration of chromium-doped β-C_2S and calcium chromium oxide hydrate (CaCrO_4·2H_2O) during the hydration of chromium-doped Portland cement indicates the substitution of chromium for silicon in hydration products. The chromium ion, Cr~(3+) , is thus stabilized and solidified through this mechanism.