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A platform for research: civil engineering, architecture and urbanism
Effect of calcium chloride on the hydration and leaching of lead-retarded cement
The effect of adding CaCl2 to ordinary portland cement containing 10% (by weight) of a synthetic lead hydroxide waste has been investigated using differential thermal analysis, conduction calorimetry, and by analysing solutions extracted from mixes during the early stages of hydration. Lead wastes are known to retard initial cement hydration reactions, and for the waste loading used in these experiments the peak in the heat of hydration curve was delayed from 8.7 to 172 h. The addition of CaCl2 reduced this retarding effect but was associated with a decrease in the overall extent of cement hydration, particularly at high CaCl2 concentrations. The acceleration induced is associated with lower concentrations of hydroxyl ions in solution. This reduces dissolution and subsequent adsorption of Pb(OH)3- ions onto C-S-H surfaces forming around hydrating cement particles. Samples containing CaCl2 show significantly higher weight loss during leaching in 0.05 N acetic acid solutions. This observation, combined with the overall reduced level of hydration, suggests that addition of CaCl2 does not produce improved materials for disposal.
Effect of calcium chloride on the hydration and leaching of lead-retarded cement
The effect of adding CaCl2 to ordinary portland cement containing 10% (by weight) of a synthetic lead hydroxide waste has been investigated using differential thermal analysis, conduction calorimetry, and by analysing solutions extracted from mixes during the early stages of hydration. Lead wastes are known to retard initial cement hydration reactions, and for the waste loading used in these experiments the peak in the heat of hydration curve was delayed from 8.7 to 172 h. The addition of CaCl2 reduced this retarding effect but was associated with a decrease in the overall extent of cement hydration, particularly at high CaCl2 concentrations. The acceleration induced is associated with lower concentrations of hydroxyl ions in solution. This reduces dissolution and subsequent adsorption of Pb(OH)3- ions onto C-S-H surfaces forming around hydrating cement particles. Samples containing CaCl2 show significantly higher weight loss during leaching in 0.05 N acetic acid solutions. This observation, combined with the overall reduced level of hydration, suggests that addition of CaCl2 does not produce improved materials for disposal.
Effect of calcium chloride on the hydration and leaching of lead-retarded cement
Cheeseman, C.R. (author) / Asavapisit, S. (author)
Cement and Concrete Research ; 29 ; 885-892
1999
8 Seiten, 15 Quellen
Article (Journal)
English
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