Water Demand of Concrete Recycled Aggregates

The procedure of designing the composition of concrete with the method of three equations demands to accept the assumptions regarding the consistence of concrete mixture. For the assumed consistency the water demand of aggregates and water demand of concrete is specified. In case of natural aggregates (NCA) the formulas, among others, of Sterne's of Bolomey's are used conditioning the water demand of aggregates from its granulation, kind and consistence of concrete mixture. There is lack of such dependencies in case of water demand of recycled aggregates (RCA). In such case there remains the empirical determination of the water demand, which in practice disqualifies the usefulness of the method of three equations to specify the concrete composition of on RCA aggregates. A way to solve this problem is looking for the relations between RCA water demand and its other qualities which are easy to specify in laboratory conditions in short time. The quality which gives such a chance to achieve this relation is the aggregates resistance to crushing whose measure is crushing indicator. This paper has made an attempt at specifying the manner of empirical definition of RCA water demand.