Reuse of 3D Additive Manufacturing Concrete Scrap in Construction

The paper studies the possibility of reusing fine concrete scrap of 3D additive production obtained by grinding fractions of various sizes. The ability to hydrate hardening depended on the size of the crushed fractions of concrete scrap. The greatest strength and ability to hydration hardening was shown by the pulverized fraction, which includes the largest number of fine particles of the cement matrix of concrete with the maximum content of non-hydrated particles of alite and belite. Then the strength is followed by samples of cement stone obtained by grinding the largest fractions (2.5–5 and 1.25–2.5 mm), in which the content of quartz increases and the content of alite and belite decreases. The minimum compressive strength was shown by samples of cement stone obtained by grinding fractions (0.16–0.315, 0.315–0.63 and 0.63–1.25 mm), in which quartz prevails and traces of alite and belite are observed. The strength of solidified samples is mainly due to coagulation bonds, which significantly weaken when wet. The water resistance of cement stone samples varies depending on the hydration capacity of the powdered material fractions. It is shown that the use of crushed concrete scrap as a binder requires additional measures to increase the strength and water resistance.