CC BY
22UDC 693.547.6.
MOISTURE LOSS FROM FRESHLY LAID CONCRETE DEPENDING ON THE TEMPERATURE AND HUMIDITY OF
THE ENVIRONMENT
1A. Khamidov, 2S. Khakimov
1Professor of Namangan Institute of Engineering and Construction 2Teacher at Namangan Institute of Engineering and Construction https://doi.org/10.5281/zenodo.7880127
Abstract. This article highlights the issues of studying moisture loss from freshly laid concrete depending on the temperature and humidity of the environment, presents the results of studies of various film-forming compositions used to protect freshly laid concrete from moisture loss.
Keywords: climate, temperature, humidity, concrete, cement, film-forming compounds, water- cement ratio, loss of kinetics, protection.
INTRODUCTION
Areas with a dry and hot climate are characterized by low relative air humidity in the daytime (up to 15-30%) and high temperatures exceeding 40 ° C in the shade. At the same time, cyclic changes in relative air humidity during the day reach 70% or more, and daily temperature drops on the surface of structures heated during the day by direct solar radiation lie in the range of 30-50°C [1].
The process of dehydration of hardening concrete in a dry and hot climate at an early age is the most characteristic feature of keeping it in an environment with high temperature and low humidity. Therefore, the question of studying the intensity of concrete dehydration and the time of stabilization of moisture loss, i.e. the study of the kinetics of moisture loss is important for creating favorable temperature and humidity conditions for curing concrete [2].
RESEARCH MATERIALS AND METHODOLOGY
In these studies, the question of the influence of changes in temperature and humidity conditions on the moisture-proof properties of film-forming materials was studied.
The main studies were carried out on heavy concrete of class B 25 (corresponding to grade M300) of the following composition: 1:2.25:3.38. The water-cement ratio of the concrete mixture was 0.57; cone draft 4-5 cm (concrete of such grades and composition is widely used in Central Asia in the construction of engineering structures and industrial buildings). And preliminary studies were carried out on samples prepared from a cement-sand mortar with W/C = 0.45. The composition of the sand-cement mortar was adopted as 1:3, since studies have shown that a change in the proportion of sand does not have a noticeable effect on the kinetics of moisture loss and this composition is most often used in construction.
As a binder in the preparation of concrete and cement-sand mortars, Portland cement grade M400 from the Kuvasay cement plant (Uzbekistan) was used with the following characteristics: normal density 25.87; the beginning of setting - 2 hours 34 minutes, the end of setting - 3 hours 50 minutes. Mineralogical and chemical composition of cement are given in tables 1 and 2.
Table 1
Mineralogical composition of Portland cement
Content, in %
Manufacturer СзS C2S СзА C3AF
Kuvasay cement plant 56 16 7 16
Table 2
Chemical composition of Portland cement, in %
SiO2 Fe2O3 ^2O3 CaO MgO SO3 K2O Na2O Пппп
227,62 33,07 66,88 53,11 5,07 3,46 0,70 0,41 00,48
Granite crushed stone with a fraction of 5-20 mm was used as a coarse aggregate, and
quartz river sand with a fineness modulus of 1.8-2.0 was used as a fine aggregate.
The following compositions were taken as the main film-forming materials for research:
- water-soluble composition (WRC) based on acetone-formaldehyde resin [3];
- water-dispersed composition (WDC) based on styrene-butadiene latexes BS-85M and BS-60M [4];
- composition (CP) based on lacquer brand HP-734 - a solution of chlorosulfonated polyethylene in xylene (solvent, toluene, stabilized with epoxy resin) [5].
RESULTS OF THE STUDY
The research was carried out in the following way. Samples-cubes, 150x150x150 mm in size, were prepared from a cement-sand mortar. Film-forming materials were applied to the surface of freshly prepared samples with a paint sprayer (consumption 400 g/m2). The prepared figurines were placed in various conditions of keeping - in a climatic chamber with t=60°C and =30%; and with t=40°C=30%; into the chamber of normal hardening (t=20°C; =95-98%).
The kinetics of moisture loss in the samples was studied by the following new
method.
This technique allows studying the effect of film-forming materials on the kinetics of moisture loss and consists in determining moisture loss for a given time from cement-sand mortar samples after applying film-forming materials to their surface.
To study the kinetics of moisture loss from the cement-sand mortar, the samples are weighed after 1, 2,...,7 and 24 hours after applying the film-forming material and placing them in the holding chamber. Calculation of moisture loss kinetics is carried out according to the following formulas:
Mixing water losses from samples of cement-sand mortar when using a film-forming material (FP) are determined by the following formula:
where mp is the loss of mixing water from the samples after applying the film-forming material, in g
— sample weight after applying the film-forming material, in g; Q 7 — sample weight at the time of moisture loss determination, in g; 7 — time for determining moisture loss, h;
Q ~ the amount of water (solvent) contained in the film-forming material, in g; b — the amount of mixing water in the sample, in g;
(3)
— weight of the sample before applying the film-forming material, in g;
V- the amount of mixing water in the formulation of the cement-sand mortar, in% P ~ weight of paraffin embedded along the edges of the sample, in g; O — weight of the form, in g.
For control samples, the mixing moisture loss (B) is determined by the formula:
b 100(4)
Where Til — mixing water losses from samples (without film-forming material, in g)
The results of the calculation were entered into a table and a graph of moisture loss from the cement-sand mortar was plotted depending on the time and conditions of exposure, as well as the type of film-forming material. The technique makes it possible to study the kinetics of moisture loss of a cement-sand mortar, when using film-forming materials as moisture-proof coatings.
50 40 30 20 10 0
_ 1K
1 2 3 4 5 6 7
Fig.1. Kinetics of moisture loss from concrete samples depending on the temperature and
humidity conditions of keeping 1k, 2k and 3k samples without coating; 1, 2 and 3 - samples under VRK, VDK, KhP;
1 and 1 k - chamber of normal hardening;
2 and 2 k - climatic chamber /t=40°C; <P =30%/,
3 and 3 k - climatic chamber /t=60°C; <P =30%/.
From the graphs in Fig. 1 it can be seen that the protective ability of the compositions with an increase in temperature and a decrease in the humidity of the environment deteriorates somewhat.
The value of moisture loss from the samples was determined after 7 hours of exposure. Table 3 shows the results of determining the influence of temperature and humidity conditions on the protective ability of film-forming materials.
Таble 3
Influence of temperature and humidity conditions on the protective ability of film-forming
materials
Moisture loss, % after 7 hours of storage in the chamber
№ Compositions normal hardening t-20°C, -=95-98% Climatic
t=40°C, =30% t=60°C, =30%
1 VRK 3,00 4,60 6,71
2 VDK 3.49 5.02 6.60
3 HP 3.01 4.10 6.29
4 Concrete without care 22.79 35.66 44.00
From the data given in the table, it can be seen that with an increase in the holding temperature, the protective ability of the film-forming materials deteriorates. However, this
deterioration is within the permissible norm of moisture loss (up to 10%). At the same time, significant moisture losses are observed in untreated concrete: with normal hardening 22.79%, in the climatic chamber 33.66 and 44%.
CONCLUSION
According to moisture loss, one can judge the strength of concrete. When using film-forming compounds in concrete, cement hydration occurs under favorable conditions, which contributes to the achievement of grade strength. In the absence of care in concrete as a result of significant moisture loss, cement hydration decreases, resulting in a decrease in strength (sometimes up to 50%) [6].
Analyzing the results of experimental studies, it can be concluded that with an increase in the holding temperature, the protective ability of film-forming materials deteriorates, but the amount of moisture loss does not exceed the permissible value.
REFERENCES
1. Хамидов, А. И., Нуманова, С. Э., & Жураев, Д. П. У. (2016). Прочность бетона на основе безобжиговых щёлочных вяжущих, твердеющего в условиях сухого и жаркого климата. Символ науки, (1-2), 107-109.
2. Khamidov, A., Akhmedov, I., Shavkat, Y., Jalalov, Z., Umarov, I., Xakimov, S., & Aleksandr, K. (2022). APPLICATION OF HEAT-INSULATING COMPOSITE GYPSUM FOR ENERGY-EFFICIENT CONSTRUCTION. Spectrum Journal of Innovation, Reforms and Development, 10, 77-84.
3. Хамидов, А. И., Ахмедов, И. Г., Мухитдинов, М. Б., & Кузибаев, Ш. (2022). Применение теплоизоляционного композиционного гипса для энергоэффективного строительства.
4. Kholmirzayev, S., Akhmedov, I., Khamidov, A., Yusupov, S., Umarov, I., & Hakimov, S. (2022). ANALYSIS OF THE EFFECT OF DRY HOT CLIMATE ON THE WORK OF REINFORCED CONCRETE ELEMENTS. Science and innovation, 1(A8), 1033-1039.
5. Нуриддинов, А. О., Ахмедов, И., & Хамидов, А. И. (2022). АВТОМОБИЛ
ЙУЛЛАРИНИ ^УРИЛИШИДА ИННОВАЦИЯЛАР. Academic research in educational sciences, 3(TSTU Conference 1), 211-215.
6. Хамидов, А. И., Мухитдинов, М. Б., & Юсупов, Ш. Р. (2020). Физико-механические свойства бетона на основе безобжиговых щелочных вяжущих, твердеющих в условиях сухого и жаркого климата.
7. Хамидов, А. И., Ахмедов, И., Юсупов, Ш., & Кузибаев, Ш. (2021). Использование теплоизоляционного композиционного гипса в энергоэффективном строительстве.
8. Хамидов, А. И., Ахмедов, И., & Кузибаев, Ш. (2020). ТЕПЛОИЗОЛЯЦИОННЫЕ МАТЕРИАЛЫ НА ОСНОВЕ ГИПСА И ОТХОДОВ СЕЛЬСКОГО ХОЗЯЙСТВА.
9. Хамидов, А. И., Ахмедов, И. Г., Мухитдинов, М. Б., & Кузибаев, Ш. (2022). Применение теплоизоляционного композиционного гипса для энергоэффективного строительства.
10. Хамидов, А. И., & Ваккасов, Х. С. (2018). ИСПОЛЬЗОВАНИЕ ГЕЛИОТЕХНОЛОГИЙ ДЛЯ УСКОРЕНИЯ ТВЕРДЕНИЯ БЕТОНОВ НА ОСНОВЕ БЕЗОБЖИГОВЫХ ЩЁЛОЧНЫХ ВЯЖУЩИХ. Вестник Науки и Творчества, (2 (26)), 45-47.
11. Arifjanov, A., Akmalov, S., Akhmedov, I., & Atakulov, D. (2019, December). Evaluation of deformation procedure in waterbed of rivers. In IOP Conference Series: Earth and Environmental Science (Vol. 403, No. 1, p. 012155). IOP Publishing.
12. Arifjanov, A., Akmalov, S., Akhmedov, I., & Atakulov, D. Evaluation of deformation procedure in waterbed of rivers.(2019) IOP Conference Series: Earth and Environmental Science, 403 (1). DOI: https://doi. org/10.1088/1755-1315/403/1/012155.
13. Arifjanov, A. (2021). Innovative technologies in the assessment of accumulation and erosion processes in the channels. Turkish Journal of Computer and Mathematics Education (TURCOMAT), 12(4), 110-114.
14. Arifjanov, A., Babajanov, F., Akhmedov, I., Fozilov, O., & Umarov, I. (2023). Analysis results of data obtained in natural field research in mountain river Sokhsoy. In E3S Web of Conferences (Vol. 365, p. 03017). EDP Sciences.
15. Xakimov, S., & Dadaxanov, F. (2022). STATE OF HEAT CONDUCTIVITY OF WALLS OF RESIDENTIAL BUILDINGS. Science and innovation, 1(C7), 223-226.
16. Yuldashev, S., & Xakimov, S. (2022). ТЕМИР ЙУЛ ТРАНСПОРТИДАН КЕЛИБ ЧИ^АДИГАН ТЕБРАНИШЛАР ХДВДДА. Science and innovation, 1(A5), 376-379
17. Yuvmitov, A., & Hakimov, S. R. (2021). Influence of seismic isolation on the stress-strain state of buildings. Acta of Turin Polytechnic University in Tashkent, 11(1), 71-79.
18. Шаропов, Б. Х., Хакимов, С. Р., & Рахимова, С. (2021). Оптимизация режимов гелиотеплохимической обработки золоцементных композиций. Матрица научного познания, (12-1), 115-123.
19. Ювмитов, А. С., & Хакимов, С. Р. (2020). ИССЛЕДОВАНИЕ ВЛИЯНИЯ СЕЙСМОИЗОЛЯЦИИ НА ДИНАМИЧЕСКИЕ ХАРАКТЕРИСТИКИ ЗДАНИЯ. Acta of Turin Polytechnic University in Tashkent, 10(2), 14.
20. Хакимов, С. (2022). АКТИВ ВА ПАССИВ СЕЙСМИК УСУЛЛАРИ ХДМДА УЛАРНИНГ АСОСИЙ ВАЗИФАЛАРИ. Journal of Integrated Education and Research, 1(2), 30-36.
21. Хакимов, С., Шаропов, Б., & Абдуназаров, А. (2022). БИНО ВА ИНШООТЛАРНИНГ СЕЙСМИК МУСТА^КАМЛИГИ БУЙИЧА ХОРИЖИЙ ДАВЛАТЛАР (РОССИЯ, ЯПОНИЯ, ХИТОЙ, А^Ш) МЕЪЁРИЙ ХУЖЖАТЛАРИ ТАХЛИЛИ. BARQARORLIK
VA YETAKCHITADQIQOTLAR ONLAYNILMIY JURNALI, 806-809.
22. Akhmedov, I., Khamidov, A., Kholmirzayev, S., Umarov, I., Dedakhanov, F., & Hakimov, S. (2022). ASSESSMENT OF THE EFFECT OF SEDIBLES FROM SOKHSOY RIVER TO KOKAND HYDROELECTRIC STATION. Science and innovation, 1(A8), 1086-1092.
23. Ахмедов, И., Ризаев, Б., Хамидов, А., Холмирзаев, С., Умаров, И., & Хакимов, С. (2022). ПЕРСПЕКТИВЫ РАЗВИТИЯ ЖЕЛЕЗОБЕТОННЫХ КОНСТРУКЦИЙ В УЗБЕКИСТАНЕ. Journal of new century innovations, 19(6), 60-70.
24. Ризаев, Б., Ахмедов, И., Хамидов, А., Холмирзаев, С., Хакимов, С., & Умаров, И. (2022). ВЛИЯНИЯ ТЕМПЕРАТУРНО-ВЛАЖНОСТНОГО РЕЖИМА НА ВОДОПОГЛОЩЕНИЕ ЛЕГКИХ БЕТОНОВ НА ПОРЫСТЫХ ЗАПОЛНИТЕЛЯХ. Journal of new century innovations, 19(8), 192-201.
25. Ризаев, Б., Ахмедов, И., Хамидов, А., Холмирзаев, С., Хакимов, С., & Умаров, И. (2022). ЖАХОНДА КИЧИК ГЭСЛАРНИ РИВОЖЛАНТИРИШНИНГ ХОЗИРГИ ЗАМОН АНЪАНАЛАРИ. Journal of new century innovations, 19(8), 110-119.
26. Холмирзаев, С., Ахмедов, И., Адхамжон, X,., Ризаев, Б., Умаров, И., & Хакимов, С. (2022). ^УРУ^ ИССЩ ЩЛИМЛИ ШАРОИТЛАРДА ^УРИЛГАН ВА ФОЙДАЛАНАЁТИЛГАН БЕТОНЛИ ВА ТЕМИР БЕТОН КОНСТРУКЦИЯЛАРНИ ХОЛАТИ. Journal of new century innovations, 19(7), 180-190.
27. Ахмедов, И., Ризаев, Б., Хамидов, А., Холмирзаев, С., Умаров, И., & Хакимов, С. (2022). ДЕФОРМАТИВНОСТЬ ЖЕЛЕЗОБЕТОННЫХ КОЛОНН ИЗ ТЯЖЕЛОГО БЕТОНА В УСЛОВИЯХ СУХОГО ЖАРКОГО КЛИМАТА. Journal of new century innovations, 19(6), 171-182.
28. Bakhodir, R., Islombek, A., Adhamjon, K., Sattor, K., Isroiljon, U., & Sodikjon, K. (2022). CALCULATION OF DEFORMATION CHANGES OF CENTRALLY COMPRESSED REINFORCED CONCRETE COLUMNS IN DRY HOT CLIMATIC CONDITIONS. Journal of new century innovations, 19(6), 162-170.
29. Хамидов, А., Ахмедов, И., Холмирзаев, С., Ризаев, Б., Умаров, И., & Хакимов, С. (2022). ИССЛЕДОВАНИЕ СВОЙСТВ БЕТОНОВ НА ОСНОВЕ НЕГОРЮЧИХ ЩЕЛОЧНЫХ ВЯЖУЩИХ КОНСТРУКЦИЯХ. Journal of new century innovations, 19(6), 123-134.
30. Ахмедов, И., Ризаев, Б., Хамидов, А., Холмирзаев, С., Умаров, И., & Хакимов, С. (2022). АНАЛИЗ ВЛИЯНИЯ СУХОГО ЖАРКОГО КЛИМАТА НА РАБОТУ ЖЕЛЕЗОБЕТОННЫХ ЭЛЕМЕНТОВ. Journal of new century innovations, 19(6), 39-48.
31. Bahodir, R., Islombek, A., Adhamjon, H., Sattor, K., Isroiljon, U., & Sodiqjon, H. (2022). INFLUENCE OF AGGRESSIVE MEDIA ON THE DURABILITY OF LIGHTWEIGHT CONCRETE. Journal of new century innovations, 19(6), 318-327.
32. Крылов Б.А., Хамидов А. Вопросы повышения качества бетонных и железобетонных конструкций в условиях сухого и жаркого климата. В кн. Тезисы докладов 3-го координационного совещания «Расчёт, проектирование и испытание железобетонных конструкций, предназначенных для эксплуатации в условиях сухого и жаркого климата», Наманган, 1986 год.
33. Хамидов А., Мухитдинов М., Хамидов Д. Особенности технологии бетонных работ в условиях сухого и жаркого климата при использовании плёнкообразующих покрытий. Монография, Ташкент LESSONPRESS 2019.
