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박찬식,김종범,오재일 중앙대학교 건설산업기술연구소 2000 건설산업기술연구소 논문집 Vol.1 No.-
Frequently, wasted concrete was crushed into coarse and fine aggregates for recycling purpose such as pavement materials. However, fine aggregates and/or powders have weak physical strength and absorb much moisture than coarse one, which make them useless for this purpose. In order to avoid just wasting these materials in a confined area, it is worthy to find the usefulness of theae materials which consist of much cement-paste than the other. One of the major component of wasted concrete element is CaO (approximately 30%) which can neutralize acidic solution like limestone(95% of CaO). ANP(Acid Neutralization Potential) and metal-leaching characteristics of recyled concrete aggregate were investigated. Random samples were collected for three months, and then classified with the period of scooping and their diameter sizes(9.52<D<12.7 ㎜, 4.75<D<9.52 ㎜, and D<4.75 ㎜). After pulverizing these distinguished samples, #200-sieve was used to get 1g of power of each sample. Neutralization experiment was carried out with these sample into the acidic solution(pH=1.758, 100 ㎖), respectively. pH difference was monitored right away and 10% solution was decanted for further metal ion analysis. Recycled concrete aggregates showed the neutralizing potential and sample size (diameter) was the one of the major factors, resulting 20% difference of ANP in this test. It was assumed that the surface area for reaction and the content of cement-paste were the main reason of this result. Also, the metal leaching properties of all samples were analyzed to determine the concentrations of As, Cr, Zn, Pb, Mn, Fe, Cu, and Al. It was found that the concentration of metal ions was dependent on pH of the solution. At neutral of alkaline pH conditions, there would be little leaching of metal ions and minor environmental problem.