THE EFFECT OF POLYDISPERSE CONCRETE SCRAP OF 3D PRINTING ON THE STRUCTURE FORMATION OF CONCRETE

Abstract

The article considers the influence of polydisperse concrete scrap of 3D printing on the structure formation of concrete during its repeated application. It is established that the favorable effect on the strength is due to the presence of thin layers on the surface of the secondary fine aggregate in the form of hydrate phases that enhance adhesion to the forming cement matrix. At the same time, an important multifunctional role is played by a fine fraction consisting of a cement matrix with a small amount of pulverized clinker and quartz. It increases the volume of the binder part; performs the function of the centers of crystallization of hydrate phases; promotes the formation of a compact and homogeneous structure by filling the pores; increases the strength due to the hydration of the minerals alite and belite. It is shown that the minimization of the voidness of the fine-grained part of the concrete scrap is largely due to the polymodal grain composition, which contributes to the optimization of the structure of fine-grained concrete and increases the strength. The features of the microstructure of fine-grained concrete samples are established. Artificial conglomerate based on concrete scrap is characterized by a compact structure, due to the high adhesion of the fine aggregate to the cement matrix of concrete, filling the pores with hydrate phases and fine particles, in contrast to the samples of fine-grained concrete of the control composition, which structure is characterized by a weak contact zone between the aggregate and the cement matrix.