: 57-62
Lviv Polytechnic National University, Department of Building Production

The article considers the use of alkaline accelerators of hardening in the construction industry. The influence of alkaline accelerator on the basis of sodium aluminate on the physical and mechanical properties of fine-grained concrete has been investigated. It has been shown that the including of alkali accelerator of hardening Na [Al (OH)4] leads to an increase in water consumption and reducing the strength of the binding agent in the all terms of hardening. The method of mathematical planning of the experiment determined that an optimum content of 1.5 mas.% of aluminum-containing alkaline accelerator and 1 mas.% superplasticizer of polycarboxylate type PCЕ ensures the production of fine-grained concrete with high early strength. Due to experimental researches was determined that optimal content of Na [Al (OH)4] – 1.5 % and PCЕ – 1 % provides the production of modified concrete with high early strength – after 1 day flexural strength – 4.7 MPa, compressive strength – 15,9 MPa. It has been shown that the introduction of an accelerator based on aluminate and PCЕ leads to an acceleration of hydration for 5 hours and a decrease in temperature to 60 °C. It has been shown that the mechanism of action of sodium aluminate in the cemetery system consists in the rapid formation of the product of hydration of the ettringitе. The system of Ca(OH)2-Na [Al(OH)4] – CaSO4.2H2O was investigated by the method of X-ray diffraction analysis and it
was determined the presence of intense reflexes of ettringitе. The introduction of an alkaline accelerator based on sodium aluminate into the composition of concrete allows them to accelerate their hardening and increase the early strength, and the use of composite cement – provides improved operational properties. Using of alkaline accelerator based on sodium aluminate in concrete technology creates the possibility of obtaining sprayed concrete and mortars for gunning, and also the rapid implementation of repair and renovation works.

1. Xu Qi., Stark J., Finger F. A. (2008). A model of early cement hydration with an alkaline setting accelerator. Cement international, 1, 67-74.

2. Han J., Wang K., Shi J., Wang Y. (2014). Influence of sodium aluminate on cement hydration and concrete properties. Construction and Building Materials, 64, 342–349.

3. Bier A., Amathieu (1997). Calcium Aluminate Cement (CAC) in Building Chemistry Formulations. In: Proceedings of Conchem, Düsseldorf.

4. Kropyvnytska T., Semeniv R., Kotiv R., Kaminskyy A., Gots V. (2018). Studying the effect of nano-liquids on the operational properties of brick building structures. Eastern-European Journal of Enterprise Technologies, 5/6(95), 27–32.

5. Krol M, Tur W. (1999) Beton ekspansyvny. Arkady, Warszawa, 240.

6. Morioka M., Higuchi T., Hori A., Sakai E. (2008). Characteristics of Rapid – Hardening Mortar Added with Amorphous Calcium Aluminate. In: Transactions Von einander lernen – Innovationen in Bauchemie und Lackchemie (in Koblenz), 263–271.

7. Andersen M. D., Jakobsen H. J., Skibsted J. (2005). Characterization of white Portlandcement hydration and the C–S–H structure in the presence of sodium aluminate by 27Al and 29Si MAS NMR spectroscopy. Cem. Concr. Res., 34(5), 857–68.

8. Li Y. S., Lima D. S., Chunb B. S., Ryou J. S. Characterization of a sodium aluminate(NaAlO2)-based accelerator made via a tablet processing method. J. Ceram. Process. Res., 14(1), 87–91.

9. Sanytsky М. А., Yakymechko Ya. B. (2013). Koncepcia pidvyshchennia efektyvnosti nehashenoho vapna v budivelnykh kompozytsiiakh. Stroitelnie materialy i izdeliia, 2, 4–6.

10. Sanytsky М. А., Sobol Kh. S., Markiv Т. Ye. (2010). Modyfikovani kompozytsijni cementy. Lviv: Vydavnytstvo Lviv. Politekhniky, 132.