APPLICATION IN CONCRETE PLANTS WASTES RECOVERED FROM CONCRETE INDUSTRY

摘要

To meet environmental criteria, wastes from concrete industry are often reused in concrete plants. There are both wastes actually produced in concrete plants (fresh concrete) and also old concretes obtained from destroyed structures. At first aggregate is recovered from fresh concretes by rinsing with water and then the rest is collected as a waste sludge containing some solid material. The reuse of recovered aggregates is not a problem, but application of the sludge makes some difficulties. The main criterion of waste water which is reused as mixing water in concrete industry is the density. Water often contains solid material. Practically the density of sludge can reach the level above 1.4 kg/l, but then it should be mixed with clean water. Another way is to separate the solid material from the sludge. Investigations of solid material from waste water by Differential Thermal Analysis, X-Ray Diffraction Method and another chemical analytical method were carried out and the results are presented. Chemical admixtures which are widely used in concrete industry are often neglected in the aspect of waste water quality used as mixing water. The effects of action between lignosulfonate and naphthalene based admixtures and cement were investigated. Chemical changes in the composition of water being in the contact with cement grouts caused by the presence of admixtures were observed.