EFFECT OF COMPLEX ADDITIVE ON EXOTHERMIC KINETICS AND HYDRATION STAGES OF CEMENT SYSTEMS

Abstract

The influence of complex additives on the kinetics of cement exothermia and the stage of
cement hydration at hardening of heavy concrete in industrial conditions has been studied. It is established
that in heavy concrete B35 with the use of cement CEM I 42.5 N SS with complex admixture maximum
temperature of hydration - 79.0 ° C reaches 26 hours 30 minutes after pouring and preservation of maximum
temperature within 78.0-79.0 ° C continues for 9 hours. Complex additives significantly increase the degree
of hydration of cement. At the same time, the initial hardening time is 4-4.5 % and 28 day hardening age is
up to 15 %. It is established that the introduction of complex additive in the cement composition of CEM I
42.5 N SS promotes the formation of smaller and mostly oriented secondary crystals of Portlandite. The
considered complex additives consisting of the active mineral additive (wastes of enrichment of polymetallic
ores), nanofiller (microsilica) and chemical additives (master air 200 and master rheobuid 1000) changing
speed of hydration and time of achievement of the maximum temperature index, define the periods of hydrate
formation.