Impact crushing of concrete for liberation and recycling

A test rig (large-scale pneumatic cannon) has been designed, constructed and tested. This apparatus allows the adjustment of intensive stressing conditions, e.g., impact and double impact, single and multiple stressing, velocity and energy. The accelerating tube diameter limit was given by the condition of a representative feed sample (model concrete spheres 150 mm sample diameter limited by an upper particle size of aggregate d o=16 mm). The crushed fragments are described as subcollectives (truncated logarithmic normal distributions) of a multimodal distribution function. For impact stressing, liberation grades between 0.3 and 0.6 (0% adherent hardened cement paste) as well as more than 0.9 (0–50% adherent hardened cement paste) were obtained.