Contribution to the Prediction of the Recycling Potential of Recycled Concrete as a Cement Admixture Based on the Compressive Strength of the Parent Concrete

When processing construction and demolition waste, determining the most effective waste management, potential use and recycling method for the identified materials is a key element. To do this, it is necessary not only to determine the type of materials, but also knowledge which aspects of the quality of the original materials are relevant for recycling and the ability to determine the values of these parameters as easily and quickly as possible, directly during demolition activities, is highlighted as an effective tool. This paper, intended as a case study, focuses on the evaluation of the effect of finely ground parent concrete as a cement component, the main objective being to find out whether the differentiation of the quality of the parent concrete, by compressive strength, plays a significant role. The parent concrete, the powder prepared from it, and the new standard mortar mixes, were analysed to obtain a comprehensive picture of the possibility of predicting the properties of the mixes based on the strength of the parent concrete. In general, no clear effect of the parent concrete strength on the flexural strength, compressive strength, water absorption, and ultrasonic pulse velocity values of the new generation mortar was observed. However, finely ground recycled concrete have shown a nice potential to be incorporated in Portland fine-grain cements, reaching strength classes 32.5 and 42.5. Care and precise verification require a 25% replacement, especially in the case of low strength parent concrete.