Abstract
Recently, in the concrete field, the use of industrial wastes for concrete materials is expected for environmental reasons. However, these wastes may contain hazardous heavy metals. It is well known that cement paste has an ability to fix heavy metal ions, whereas it was also found that absorbed heavy metal ions can easily leach from cement paste in the presence of a CaCl2 solution. The present study aims to investigate the lead leaching behaviours from hardened cement pastes in various chloride solutions by tank leaching tests. The water-to-cement ratios of the cement paste specimens were 0.40 and 0.55. Lead was added to the cement pastes at 1 mass% of cement. Each chloride solution for the tank leaching test had three kinds of concentrations (5%, 10%, and 20%). After the tank leaching tests, the chemical changes of the specimens were analysed to discuss the effect of co-existing ions in the solutions. The results indicate that the cumulative lead leaching amount is related to the types of chloride solution as well as the concentrations of the solutions. The lead leaching amount in the CaCl2 solution was much higher than that in other solutions.
Highlights
A recycling-oriented society is required to solve environmental issues
3.1 Lead leaching amount The cumulative leaching amounts of lead from the cement paste specimens with water to cement ratios (W/Cs) of 0.40 and 0.55 immersed in CaCl2 solutions and deionized water for 64 days are shown in Fig. 2 and Fig. 3, respectively
The cumulative leaching amounts of lead from the paste specimens with W/Cs of 0.40 and 0.55 immersed in KCl and NaCl solutions and deionized water for 64 days are shown in Fig. 4 and Fig. 5, respectively
Summary
A recycling-oriented society is required to solve environmental issues. In the concrete field, the use of industrial wastes for concrete materials is expected. The leaching behaviours of lead from cement pastes immersed in three kinds of chloride solutions as well as those in deionized water were examined.
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