Determining Concrete Composition on Recycled Aggregates
The problem of recycling of construction wastes is important and at the same time difficult to deal with. One of the possible ways of using the construction wastes coming from the demolition of concrete constructions is to re-use them in the production of construction concretes as recycled concrete aggregates RCA. Determining the concrete composition with the use of RCA demands conditioning its different from the natural aggregates NA physical and mechanical properties. In the procedure of projecting the concrete composition with three equations theory the assumption of consistency class of concrete mixture is demanded. Having accepted it, the water demand of aggregates and cement is determined. In case of natural aggregates NA the formulas of Sterne's and Bolomey's are used in which aggregates water demand is conditioned from its kind and granulation and also from concrete mixture consistency. In case of RCA, there is lack of such data and each time it is necessary to determine the water demand empirically after performing a trial batch. There also exists a necessity to determine the relation between RCA water demand and its other properties which are easy to be determined in laboratory conditions and in short time. Such a property can be measured with the crushing rate wrm resistance of aggregates to crushing. Crushing rate wrm was used to qualify the recycled aggregates from recycling with the point of their potential of being re-used in constructive concrete production. It was determined a relation between crushing rate wrmand the coefficient ARCA taking place in the modified strength equation of Bolomey and thus it became possible to use the method of three equations to project the concrete composition on recycled aggregates.