• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.206-209
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• 2001

This study presents the leaching characterization of heavy metals according to changes of pH by ANC test on slag produced in electric arc furnace, bottom ash produced in coal-fired plants and their recycling products. Availability test was performed to assess the fraction of the total concentration that under worst environmental conditions could become available for leaching. TCLP, KLT(Korea Leaching Test) and KLTS(Korea Leaching Test of Soil contamination) were carried out to compare the leaching capacity and to estimate the adequacy of regulatory leaching test. Results from regulatory leaching tests could be misleading because the variable ANC of wastes can lead to very different final leachate pHs. The final pH of the regulatory test is not the ambient pH in the disposal environment, the actual solubilities of contaminants in the field may be entirely different from those predicted by these regulatory tests. Leaching behaviour of by-products was changed by recycling processes, therefore acid neutralization capacity and availability of new products, not leaching concentration by one batch regulatory test, are necessary to determine the method of recycling.

• Corrosion Science and Technology
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• v.8 no.3
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• pp.110-115
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• 2009

At the onset of corrosion of steel in concrete, hydrogen ions usually evolve in the process of electrochemical reaction, thereby decreasing the pH of the pore solution, which can be buffered by cement hydration products, as being representatively illustrated by calcium hydroxide. Hence, a fall in the pH is dependent on properties of cement hydration (i.e. hydration products and degree of hydration). The present study tested acid neutralization capacity (ANC) of cementitious binders of OPC(Ordinary Portland Cement), 30% PFA(Pulverized Fuel Ash), 60% GGBS(Ground Granulated Blast Furnace Slag), 10% SF(Silica Fume) to quantify the resistance of cement matrix to a pH fall. Cement pastes were cast at 0.4 of a free W/C ratio with 1.5% chlorides by weight of binder in cast. Powder samples obtained crushed and ground specimen after 200 days of curing were diluted in still water combined with different levels of 1M nitric acid solution, ranging from 0.5 to 20 mol/kg. Then, the pH of diluted solution was monitored until any further change in the pH did not take place. It was seen that the pH of the diluted solution gradually decreased as the molar amount of nitric acid increased. At some particular values of the pH, however, a decrease in the pH was marginal, which can be expressed in the peak resistances to a pH fall in the ANC curve. The peaks occurred at the variations in the pH, depending on binder type, but commonly at about 12.5 in the pH, indicate a resistance of precipitated calcium hydroxide. The measurement of water soluble chloride at the end of test showed that the amount of free chloride was significantly increased at the pH corresponding to the peaks in the ANC curve, which may reflect the adsorption of hydration products to chlorides.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.325-326
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• 2009

The present study concerns the acid neutralization capacity (ANC) of cement paste, mortar and concrete depending on a free water-cement ratio. The ANC of paste at 30%, 40% and 50% of water-cement ratio was measured and simultaneously the effect of aggregate on the ANC was evaluated. It was found that an increase in the acid concentration resulted in a decrease in the pH of the suspension, in particular, at 10 in the pH, a sharp decrease was observed. The ANC showed some peak resistances to acid at particular pH values.