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Effect of Hydrating Water on the Physical Characteristics and the Diffusion Release of Cesium Nitrate Immobilized in Cement

出版	ASTM International, 1992
URL	http://books.google.com.hk/books?id=VXB8zgEACAAJ&hl=&source=gbs_api

註釋The effect of the preparation procedure--(variable amounts of hydrating water on the leachability of a soluble contaminant (CsNO3) from cement samples immersed in water, as well as the physical characteristics of cement samples such as density, pore volume, and compressive strength--were considered in this work. Leach tests of cement specimens containing 2% in weight of cesium nitrate (CsNO3), prepared at different water-to-cement ratios, W/C = 0.35, 0.40, 0.45, and 0.55, were cured for 60°C, 98% RH, for eleven days. The leaching standard procedure suggested by the International Organization for Standardization (ISO) was used to follow the kinetics for the Cs+, NO3-, and Ca2+ releases from cement right cylinders, 20 mm in diameter and 20 mm high, leached in water at a solid surface-to-liquid volume (S/V) = 0.1/cm. The results of the cumulative fraction release (CFR) versus time (t) in days indicate that the leaching of soluble elements like NO3- and cesium follows a diffusion mechanism. The cumulative fraction release (CFR) values were found to depend on a porosity factor ?=(Vp)1,2,3.(Vp)0 where (Vp) 1,2,3 ... represents the total porosity of cement at the W/C considered, and (Vp)0 represents the porosity at W/C = 0.35. A diffusion coefficient, De = 1.4 x 10-7 cm2/s, calculated by the values of the cumulative fraction release at 50°C and W/C = 0.35, confirms our previous results obtained on cement samples containing CsNO3 and prepared under the same conditions.