Leachability Of Heavy Metals In Recycled Materials Of Waste Concrete

With the development of society, the protection of the environment is much moreaccounted by human beings, and effective disposal of hazardous waste containingheavy metal ion is an important component of the environmental protection work.Using cement and concrete disposing the waste also has got a lot of research andextensive practices. It makes an increase of heavy metal ions in the concrete materials.However, concrete generally used about50years will be abandoned. In order to makethe waste concrete resources, waste concrete is broken into different particle sizes tobe used as recycled aggregate by the conventional method, but in resources processsome fine powder will be produced. This fine powder will be dumped in landfillsdirectly in the practical engineering disposal. According to the data, heavy metal ionsshow different leachability under different environment conditions, the landfill islikely to cause heavy metal ion migration.In this paper, the total content of heavy metal ions in the waste concrete and themaximum effective leaching quantity of waste concrete in the typical area of ourcountry have been researched respectively by the digestion and the Netherlands"experiment of the maximum leachability".Then analyzing the leachability withdifferent particle sizes, different pH value, different of the heavy metal element of thewaste concrete recycled materials by the simulation Germany "flume method". At last,the leachability of heavy metal ions under different sources have been investigated bythe digestion and the Netherlands " experiment of the maximum leachability ".In this paper, the results show that the heavy metals contents are different indifferent areas and levels of difference is bigger with different heavy metals, thehighest Zn, the next Cu, Cr, Ni, Pb, and the minimum Cd, however, the maximumeffective leaching amount of all heavy metals is lower than the national standards.When the particle size reduced to0.15mm, heavy metals extraction content shows nodecrease with the particle size increasing, sizes displaying not obvious of influence tothe leachability; heavy metals extraction content shows an increase influence with thereduce of pH, and the effect is more apparent when the particle size larger than1mm.Different heavy metal elements have different leachability, it appearingZn>Pb>Cu>Cd>Cr≈Ni. From heavy metal ions sources, the effective leaching ofheavy metal ions scale appears adscititious metal soluble salt> natural aggregate≈gelled material.