AN NMR AND XRD STUDY OF SOLIDIFICATION STABILIZATION OF CHROMIUM WITHPORTLAND-CEMENT AND BETA-C2S/

Solidificalion/stabilization of chromium with Portland cement Type I a nd P-dicalcium silicate (beta-C2S) was investigated by means of the Si -29 solid stale Magic Angle Spinning/Nuclear Magnetic Resonance (Si-29 MAS/NMR) and X-ray Diffraction (XRD) techniques. It is found that chr omium nitrate can increase the extent of beta-C2S hydration. It is als o confirmed that the chromium ion is easily incorporated into the beta -C2S paste and hydrated Portland cement, and that it affects the chara cteristics of hydration and hydration products. Formation of beta-calc ium chromium oxide hydrate (beta-CaCrO4 . 2H2(O)) during the hydration of chromium-doped beta-C2S and calcium chromium oxide hydrate (CaCrO4 . 2H(2)O) during the hydration of chromium-doped Portland cement indi cates the substitution of chromium for silicon in hydration products. The chromium ion, Cr3+, is thus stabilized and solidified through this mechanism.