Hexavalent chromium in tricalcium silicate - Part II - Effects of Cr-VI on the hydration of tricalcium silicate

摘要

The composition and structure of hydrated tricalcium silicate (C3S)* pastes admixed with Cr-VI have been studied. The resultant mixture simulates Cr-VI waste forms stabilized in ordinary Portland cement. Scanning electron microscopy and transmission electron microscopy were used to identify the microstructural changes accompanying the addition of Cr-VI solutions to C3S. Energy-dispersive X-ray spectroscopy was used to probe the distribution of chromium in the phases within the hazardous waste forms. Elucidation of the molecular structure of the reaction products was accomplished with Fourier transform infrared and nuclear magnetic resonance spectroscopies. Cr-VI was found to be contained in the waste form as soluble Ca2CrO5 . 3H(2)O and partially VI chemically bonded within the calcium silicate hydrate (C-S-H) phase. Cr was also found to increase the condensation of C-S-H and porosity of the waste form. [References: 50]