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Section 10. Technical sciences
Adilkhodjaev Anvar Ishanovich, professor, doctor of technical sciences, vice rector for science, Tashkent Institute of Railway Engineers, Uzbekistan, Tashkent
Amirov Tursoat Jummaevich, senior lecturer, Tashkent Institute of Design, Construction & Maintenance of Automotive Roads,
Uzbekistan, Tashkent E-mail: [email protected]
NEW METHODS OF IMPROVING THE DURABILITY OF ROAD CONCRETE AND FERROCONCRETE PRODUCTS
Abstract: The article describes new ways to increase the service life of road concrete and reinforced concrete products of highways. The proposed methods increase the strength and frost resistance of concrete and reinforced concrete products with the action of chloride salts on them.
Keywords; additive, corrosion of concrete, strength reduction, frost resistance of concrete, epoxy compositions, chlorosulfonated polyethylene, adhesion, urea, modifier.
Introduction
The expansion of highway networks in the world, increasing the volume of cargo and passenger transportation, especially when the axle load is 13 tons or more in the composition of the stream, makes us think about building stronger and more durable cement concrete pavements. In addition, concrete and reinforced concrete products are widely used in order to ensure safety, arrangement and construction of artificial structures.
The main reason for the destruction of concrete and reinforced concrete products is the appearance of corrosion due to exposure to chlorides. In this regard, abroad, special attention is paid to preventing corrosion from the effects of aggressive chlorides.
Literature review
Currently, the corrosion of concrete and reinforced concrete is the most urgent problem for transport facilities. Under the conditions of concrete corrosion, the improvement of tasks on the problems of durability and reliability of building structures was studied by such world-wide researchers as M. Akiyama, M. Matsuzaki, D. H. Dang, A. Deco, V. V. Bolo-tin, L. I. Iosilevsky, V P. Chirkov, V. O. Osipov, A. A. Potapkin, I. A. Urmanov, V I. Shesterikov, S. N. Alekseev, V M. Moskvin, E. A. Antonov, S. S. Gordon et al.
In our country, under the conditions of concrete corrosion, a number of scientists have carried out research in the field of improving issues devoted to the problems of improving the durability of structures. In particular, by the reliability of building structures A.A. Ashrabov, by predicting the resource of spans of reinforced concrete bridges R.K. Mamazha-nov, T. Mukumov and N. Z. Saatova conducted research and obtained important positive results.
To date, the processes of corrosion of concrete, the relationship between the corrosion of concrete and reinforcement have been deeply studied, and recommendations have been given for taking them into account in calculations. But at the same time, work to improve the methods of exploited concrete and concrete products is still not resolved. Analysis of the above thoughts shows the lack of recommendations when using local materials in protecting concrete and reinforced concrete products from chloride salts [1].
On the roads of Uzbekistan, mainly technical salt is used, which is mined in the territory of Karakalpakstan, which is currently the cheapest and most effective anti-icing agent.
The laboratory carried out a chemical analysis of salt used on the roads of the Republic (Table 1).
Section 10. Technical sciences
Table 1. - The chemical composition of technical salts [2]
Name of the indicator The main indicators of salts
Belarus, Ukraine Karakalpakstan
Mass friction of sodium chloride 90.00% 97.11%
Mass friction of calcium - ion 0.80% 0.28%
Mass friction of magnesium - ion 0.80% 0.04%
Mass friction of sulphate 0.20% 0.75%
Mass fraction of insoluble residue in water 3.7% 0.55%
Mass friction of humidity 4.5% 1.27%
Mass friction of calium no more than 0.01% -
As can be seen from the (table 1), the salt content of anti-icing reagent-chloride salts, the road fence blocks are de-
Karakalpakstan contains more sodium chloride, which causes corrosion, than salts used in other countries. The use of salts with a high content of chlorides against ice and a low level of road maintenance can lead to a massive deterioration in the condition of concrete and reinforced concrete products and a decrease in their service life and operational reliability.
The materials and methods of research
In the experiments, glue-composition based on chlorosul-fonated polyethylene was used as a protective material, after which a transparent, elastic, glossy film was formed on the surface of the product [3]. The industry of Uzbekistan does not produce this polymer. It is purchased for hard currency. The authors of the invention allow to produce these products from local raw materials in the right quantity for consumers.
This method increases the strength and corrosiveness of products in sulfate environments. However, concrete and reinforced concrete products impregnated in this way are characterized by insufficient frost resistance in chloride salts. Due to the simultaneous action of negative temperature and
stroyed after 3-5 years of operation, without having served the service life (30-40 years), provided by the manufacturer. As a result, to ensure road safety and an aesthetic point of view, operational road services are forced to replace the destroyed blocks with new ones. This leads to unexpected costs.
Long-term monitoring of the state of the protective coating made it possible to establish that the use of glue - composition significantly increases the corrosion resistance of reinforced concrete products. However, upon receipt of chlorine gas complicates the process. In order to prevent damage to human health and the environment, compliance with relevant standards is required.
In order to eliminate these drawbacks, as well as expand the range of materials, methods have been developed to protect concrete and reinforced concrete products based on chlo-rosulfonated polyethylene and urea [3], as well as chlorosul-fonated polyethylene and polysulfide rubber [3].
The main physicomechanical properties of these composites are given in (table 2).
Table 2. - Basic physical and mechanical properties of the mixture
№ Name of the indicators Indicators
[3] [4]
1. Color mustard milky
2. Density, g/cm3 1.2 1.1
3. Operating temperature range, °C (-40) + (+100) (-40)+(+100)
4. The degree of elastic recovery,% 90-100 95-110
5. Resistance to petroleum products resistive resistive
6. Chemical resistance (acids, alkalis, salts) resistive resistive
7. Water resistance great great
8. Wear resistance great great
9. UV Resistance great great
10. Mushroom resistance great great
11. Corrosion Resistance great great
12. Adhesion score 1 1
The method is as follows. After a set of concrete and re- plied onto the surface prepared and impregnated with glyc-inforced concrete products of grade strength, a surface is ap- erin on the surface-compositions based on chlorosulfonated
polyethylene and modifier or chlorosulfonated polyethylene and urea. Preliminary surface preparation consists in removing irregularities and protrusions. In the presence of small sinks and dimples, they are leveled by grouting with a cement-sand mortar, then it is mechanically cleaned.
Results of the research
In contrast to the three-layer glycerin coating, which cracks when cracking in concrete and reinforced concrete
structures due to shrinkage, temperature and other deformations, coatings based on chlorosulfonated polyethylene, ep-oxy resin and polysulfide rubber and chlorosulfonated polyethylene and urea, having a greater elasticity can withstand cracking size 0.2-0.3 mm. The strength and frost resistance of the impregnated samples are given in (table 3).
Table 3. - Strength and cold resistance of impregnated samples
№ The name of the indicators Sample rates
Impregnated with glycerin and composition consumption, kg/u2
0.8 0.9 0.8 0.9
[3] [4]
1. Compressive resistance, MPa 385 400 390 400
2. Bending resistance, MPa 6.1 7.3 5.9 7.1
3. Frost resistance according to the second base method, cycle 275 285 280 290
Thus, the combination of features in the proposed methods allowed to obtain a positive effect, namely, that concrete and reinforced concrete products impregnated with glycerin and subsequent impregnation with a composition of chloro-sulfonated polyethylene and urea, chlorosulfonated polyethylene and polysulfide rubber increase the strength and frost resistance in chloride salts.
Conclusion
These methods help to increase the service life of concrete and concrete products, significantly reduces operating costs.
Economic efficiency of the proposed development is achieved by increasing the service life of concrete and concrete products, reducing operating costs, import substitution and saving hard currency.
In the future, measures are envisaged for the implementation of this development on the objects of roads and railways in various areas of the national economy.
References:
1. Adilkhodjaev A. I., Amirov T. J. Some ways to improve the durability of road concrete and reinforced concrete products of roads // Bulletin of TARI. Scientific and technical journal. - Tashkent. 2018. - No. 1. - P. 38-43.
2. Saatova N. Z. Residual resource of reinforced-concrete superstructures of the highway bridges subject to salt rust. Dissertation abstract of the doctor of philosophy (PhD) on technical sciences: - Tashkent, 2017. - 25 p.
3. Jalilov A. T., Karabaev A. M., Amirov T. J. et al. Method of protecting concrete and reinforced concrete products // IAP -05604. - Tashkent. Patent bulletin of Uzbekistan. - 06/29/2018. - No. 6.
