FEATURE OF NANO-ADDITIVES ON THE PROPERTIES OF RAPID HARDENING CONCRETES
It is demonstrated that the application of processing methods for the modification of their structures is one of the most innovative ways of the fast hardening concrete obtainment. It is determined that the exploitation of a complex nanomodifier on the basis of polycarboxylate superplasticizer and an innovatory hardening accelerator based on calcium silicate hydrate colloidal particles guarantees the high flowability and durability of fresh concretes. Flow characteristics of nanomodified fresh concrete determined by slump test is 210 mm with the providance of a water-reducing effect D W/C=42.6…49.1%. The stability indices (water and mortar liberation) of concrete mixtures, modified by complex nanoadmixture, are advanced compared to control concrete mixture. The concretes nanomodified by calcium silicate hydrate colloidal particles and polycarboxylate superplasticizer are featured with significant acceleration of the early strength kinetics. It is proved that nanomodified concrete can be distinguish by high early strength (specific strength (fcm<sub>2 </sub>/ fcm<sub>28</sub> = 0.63…0.72) and high strength after 28 days (85…92 MPa). The enhanced performance of fast hardening concretes is ensured by the filling up the empty space inside cementitious matrix, seeding effect whereby the C-S-H additive provides new nucleation sites within the pore space between the cement particles, high water reducing effect connected with an efficient dispersion effect of polycarboxylates. Designed nanomodified concretes are Rapid hardening high strength ones. The application of a complex nanomodifier enlarges the effectivenes of Portland cement usage in concrete (specific expenditure of Portland cement is 4.1…4.8 kg/MPa).