Papers by Keyword: BCR

Abstract: The presence of gypsum in the soil will cause problems if the source of freshwater is available and permeable soil permitting significant movement of water is to take place. The solubility of gypsum by excess water from irrigation or localized leak into the gypseous soil may cause cavity formation. In this research, a model was developed for governing the mass-transport to assess the variation of gypsum content of the soil during dissolution. A general three-dimensional finite element program (PLAXIS tunnel) was selected for the numerical analysis method to generate the solution. Parameters that affect the bearing capacity of a square footing represented by the gypsum content, the cavity volume, and the location of the cavity which represent by three offset distances from the footing center to the cavity center (x, y, and z), where (X) represents the horizontal distance, (Y) represents the vertical (depth) distance, and (Z) represents the diagonal distance. The main results show that the cavity location found to be the most parameter that affects the bearing capacity ratio (BCR). The minimum values are found when the cavity locates at the center of the footing base, and the lowest one (0.211) when the gypsum dissolved equal to 40%, also there is no effect of the cavity location when the ratio of (X/B) and (Z/B) exceed (3.0) for any depth and when the gypsum dissolved less than 10%. For high gypsum dissolution (more than 30%), the dimensionless ratios (X/B), (Z/B), and (Y/B) of the cavity must be more than 5.0.

Abstract: Used tires were subjected to supercritical water and supercritical water with H₂O₂. The distribution of heavy metals (Pb, Mn, Ni, Cu, Zn, Cd, Cr) in used tires and the corresponding residues were analyzed. BCR sequential extraction procedure was applied to examine the speciation of heavy metals mentioned above. The results showed that: the contents of Mn, Zn, Cu, Pb, Cd increased after supercritical water treatment while that of Cr and Ni decreased significantly. The addition of H₂O₂ was beneficial for the increase of heavy metals concentration and sequestration. The sequestration rate of Mn, Zn, Cu, Pb, Cd, Cr reached to 90% after the addition of H₂O₂, and that of Ni was much lower as 40%. The main speciation of Cr and other heavy metals were in residual form and oxidate form respectively. The speciation of all heavy metals were transferred from the unstable forms of weak acid soluble and reducible to relatively stable forms of oxidizable and residual.

Abstract: The incorporation of cadmium into clinker during the co-processing of waste with cement kiln was investigated. Cadmium contained reagent was added to the cement raw meal to produce clinkers after clinkerization process. XRD analysis and SEM-EDS analysis were employed to indentify the major mineral phase of clinker and the cadmium contained mineral phase. Leaching test, sequential extraction procedures were employed to evaluate the leaching potential of cadmium in clinker. The results show the stabilization rate of cadmium during the clinkerization process is low. The incorporation ratio of cadmium in C2S is 0.32%~1.14%, the incorporation ability of cadmium in C2S is higher than C3S. The major mineral phases of clinker with the incorporation of cadmium were CH, C3S and C2S. The average leaching concentration of cadmium of clinker was 1.4 μg/L, which was higher than the blank samples. BCR Sequential extraction procedures analysis of the clinkers show exchangeable, water and acid-soluble fraction and residual fraction were very small, while the reducible phase of cadmium was up to 95.13%.