INFLUENCE OF FINE-DISPERSED ADDITIVE FROM CONCRETE SCRAP ON STRUCTURE FORMATION OF PORTLANDCEMENT

Abstract

The object of the study is the effect of the introduction of a mineral additive (Ssp = 900 m2/kg) of the fraction (0.315–5 m) of the screening out of crushing concrete scrap into Portland cement for the production of various building products and structures. A fraction of concrete scrap of 0.315–5 mm is used in the work, since the X-ray phase analysis of various fractions of concrete scrap shows that these fractions have a rational content of non-hydrated particles of C3S and C2S. It is proved that the use of finely ground concrete scrap (Ssp = 900 m2/kg) as a mineral additive in Portland cement increaseINFLUENCE OF FINE-DISPERSED ADDITIVE FROM CONCRETE SCRAP ON STRUCTURE FORMATION OF PORTLANDCEMENT s the physical and mechanical properties of concrete. Comparative physical and mechanical indicators of the hardening of composite binders indicate that the most stable results with a uniform increase in strength is a composition with 5 % mineral additive, with an increase in strength from 2 to 7 days by 36 % and from 7 to 28 days by 46 %. It is found that the most rational are the compositions with 5 % and 10 % mineral additives providing an increase in the strength of the samples by 16% compared to the control composition. Due to the high dispersion, the mineral additive from concrete scrap acts as additional crystallization centers during the hydration of Portland cement, which leads to the creation of a skeleton coral-like structure, which additionally overgrows with submicroscopic crystals. With a specific surface area of 900 m2/kg, the best conditions are created for the formation of the primary frame and its further overgrowth with various crystalline calcium hydrates, which provide optimal density and strength.