Kaliuzhna O. Increasing the early strength of concrete reinforced concrete sleepers with complex additives

The influence of superplasticizers-polycarboxylates and their complex additives with accelerants - electrolytes and dispersion of calcium hydroxylates on the early strength of concrete for concrete of concrete sleepers has been studied. It was found that the use of superplasticizerspolycarboxylates can improve the early strength of the concrete after heat treatment, but each additive must be checked for consistency with the cement used. Approx Complex additives with accelerators in conditions of natural hardening ensure an increase in the early strength of concrete, but some of them, which accelerate natural hardening, can reduce the strength after WWTP and must be checked before use. Electron-microscopic examinations of the structure of cement stone with additives were carried out and it was found that the additive of only policarboxylate does not change the structure of hydration products. Complex additives lead to formation of additional number of crystalline hydrates of AFm- and/or AFt-phases. The scheme of development of the cement hardening process and the initial stage of cement hardening without or with additives has been developed. By means of which the highest accelerating effect of the complex addition of polycarboxylate and calcium hydroxylate dispersions was established by experimental investigations, Dispersion particles increase surface area where crystallization (condensation) of cement hydration products takes place and ensures faster filling of spaces between cement particles (mineral additives) with them, fillers) with establishment of lances with electro-heterogeneous contacts. As a result of potentiodynamic and microscopic investigations it was established that the tested additives in the dosages do not cause corrosion effect on the steel reinforcement bars. Transmission strength values of 32 MPa for sleepers after 24 years of hardening under low-heat regime and after 2 days of natural hardening have been achieved. The formula for economic efficiency of using additives to reduce the energy intensity of production of concrete sleepers has been proposed.