Stiffness Characterization of Cold Recycled Mixtures

One of the objectives within the European research project CoRePaSol (supported within the CEDR Transnational Program) was to summarize assessment and research of stiffness modulus of cold recycled mixes determined according to repeated indirect tensile stress test (IT-CY). In most cases the stiffness modulus values were compared to the values of indirect tensile strength (ITS), which is currently the most commonly used characteristic for proving the quality of a cold recycled mix. The first part of experimental measurements was focused on the standard cold recycled mixes, thus mixes whose aggregate skeleton is formed entirely by RAP and which contain either just the bituminous binder (bituminous emulsion or foamed bitumen), or a combination of one of these binders and a hydraulic binder (cement). Later also combinations with other types of recyclable materials were done and tested. Stiffness modulus and in most cases also the indirect tensile strength values were investigated from many points of view, e.g. the effect of different bituminous / hydraulic binder content on these characteristics, time-dependent progress in change of these characteristics, effect of testing temperature or the influence of fines addition on the stiffness modulus value. This paper therefore brings some summarization of the gained experience.