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0STUDY OF THE PROPERTIES OF CONCRETE MIXTURES WITH ADDED POLYCARBOXYLATE SUPERPLASTICIZERS
1Ismoilov F.S., 2Karimov M.U., 3Djalilov A.T., 4Farmanov B.I., 5Ismoilova Kh.Dj.,
6Sultonov O.K.
1Senior Researcher, PhD, Tashkent Scientific Research Institute of Chemical Technology 2Tashkent Scientific Research Institute of Chemical Technology, Doctor of Science, Professor
3Doctor of Science, Professor, Academician of the Academy of Sciences of the Republic of
Uzbekistan
^Director of Tashkent Scientific Research Institute of Chemical Technology, Kashkadarya Engineering-Economics Institute, Head of the Department of Chemical Technology, Doctor of
Sciences, Associate Professor (PhD) 5Kashkadarya Engineering-Economics Institute, Head of the Department of General and Organic Chemistry, Associate Professor, Candidate of Chemical Sciences 6PhD student, Tashkent Scientific Research Institute of Chemical Technology https://doi.org/10.5281/zenodo.14001252
Abstract. The aim of the research is to synthesize a polycarboxylate superplasticizer for the development of concrete products with rheological properties. For this purpose, a synthesis was carried out based on polyethylene glycol with isoprenyl ether (TPEG) and acrylic acid (AA). The polycarboxylate superplasticizer was prepared through solution of radical polymerization. Concrete mixtures were prepared using the synthesized superplasticizer in various amounts (0.2%, 0.4%, 0.6%, 0.8%). The chemical structure and composition of the synthesized superplasticizers were determined using IR spectral analysis.
Keywords: TPEG, Acrylic acid, Polycarboxylate, Concrete mixture, IR spectrum.
Introduction. Currently, the construction industry is developing at a rapid pace. The demands for the rational and efficient use of raw materials and energy resources are also changing. In the production of concrete products, strength and good workability hold a special place. Effectively addressing this issue requires extensive use of special chemical additives. The high efficiency of superplasticizers is related to their lack of negative effects on concrete and reinforcement, as well as their availability and low cost. Superplasticizer additives are substances with surface-active properties that improve the workability of concrete mixtures and enhance their strength. In concrete industry technology, the use of superplasticizers helps maintain the consistent workability of concrete mixtures while reducing water demand and porosity, thereby increasing density and strength. Today, there are numerous superplasticizer additives available in the global market, and their effects on cement composition and concrete can vary significantly. Synthetic oligomer-based superplasticizers are used worldwide to improve the rheological and physical-mechanical properties of composite materials, including concrete and concrete mixtures, and to regulate their structure [1].
Superplasticizers are prepared from water-soluble macromolecules as additives that reduce water consumption in concrete mixtures [2-5]. The chemical functional groups and molecular structure of superplasticizers, such as carboxyl groups, the length and density of polymer chains and side chains, positively influence the performance properties of cement mixtures in aqueous solution form [6-10]. The water-reducing and dispersing effects of polycarboxylate
superplasticizers can be modified by controlling molecular weight and adjusting the balance of hydrophilic fragments [11]. Polyester-based macromonomers, such as ro-methoxy polyethylene glycol (MPEG) and isoprenyl ether polyethylene glycol (TPEG), are widely used as common macromonomers in the synthesis of superplasticizers [12-15]. Polycarboxylate is synthesized from unsaturated carboxylic acid monomers, long-chain alkane macromers, and other raw materials. It is a highly effective cement dispersant that can be well utilized in concrete. Polyacrylate molecules contain various functional groups, such as -COOH, -SO3H, -NH2, and -OH. The hydration products of Portland cement cause these groups to adhere to its surface, disrupting the flocculation structure between silicate particles and resulting in the formation of an adsorption layer. The spatial barrier and electrostatic repulsion introduced by the added polycarboxylate superplasticizer significantly influence the interactions at the water-solid activator interface of cement particles. The uniform distribution of polycarboxylate superplasticizer particles improves flow and other chemical properties [16-19].
Methodology.
In the synthesis process, acrylic acid, hydrogen peroxide, isoprenyl ether polyethylene glycol (TPEG, molecular weight 2400), mercaptan acid (as a chain transfer agent), ascorbic acid, HEA (2-hydroxyethyl acrylate), and distilled water were used. All solvents and substances were used without additional purification.
The synthesis of the superplasticizer was carried out in three stages. It was synthesized through radical polymerization based on the AA-TPEG type. In the first stage, 50 g of TPEG and 0.35 g of hydrogen peroxide were dissolved in 100 ml of distilled water and continuously stirred in a 500 ml round-bottom flask equipped with a condenser. After raising the temperature to 65°C, in preparation for the second stage of polymerization, mercaptan (0.29 g), ascorbic acid (0.095 g), and 8.75 g of water were gradually added to the flask over a period of 2 hours.
In the third stage, during the polymerization reaction, acrylic acid and HEA were mixed with water and added to the reaction mixture over 3 hours while maintaining a constant temperature. After the reaction was completed, the reaction mixture was left in an oven at 70°C for 48 hours to determine the dry residue mass. The final product of the polycarboxylate superplasticizer was a 30% aqueous solution.
CH3
I
aH2C = CH + bH2C = C
Initiator
H2C - CH
CH3 I 3
1 CH2 | | —' a COOH — 1 - CH2
CH2 CH2 2
1 0 1 O
CH2 1 2 1 CH2
CH2 1 2 CH2 ■
O H n 1 0 1 H
]
b
n
Figure 1. Schematic representation of the preparation of polycarboxylate superplasticizer by radical copolymerization in an aqueous solution.
In this research work, cement according to GOST 30515-2013 standards was purchased from Namangan Cement Plant. The chemical composition and physical properties of the cement provided by the manufacturer are presented in Tables 1 and 2.
Table 1. Chemical Composition of Cement
CaO SiO2 AI2O3 Fe2O3 SO3 MgO K2O TiO2 Na2O Other
61.64 22.29 5.22 4.2 2.4 1.68 0.47 0.26 0.21 0.22
Table 2. Mineralogical Composition of Cement
C3S C2S C3A C4AF
59.38 15.55 7.29 11.59
In preparing the concrete mixture, the mass ratio of the polycarboxylate superplasticizer to cement was taken as 0.2%, 0.4%, 0.6%, 0.8%, and 1%. The concrete mixture without the superplasticizer was taken as the control sample. The amount of mixing water for each dosage of the polycarboxylate superplasticizer was adjusted until the initial slump reached 200 ± 15 mm. Typically, the solid materials are mixed dry for 60 seconds, after which the superplasticizer is mixed with a measured amount of water and added. The mixing process lasts for 6 minutes.
The prepared concrete mixture was analyzed for reductions in water consumption, slump, workability retention, density, and initial and final setting times. To study the strength of the concrete product, fresh concrete mixtures were cast into molds, and the molded concrete mixture was vibrated on a vibrating table for 2-3 minutes to ensure good workability. According to GOST 10180-32, the produced molds are stored at 20°C for 24 hours, after which the concrete samples are removed from the molds, and their strengths are tested at 3, 7, and 28 days.
Percentage Reduction in Water Consumption. The percentage reductions in water consumption of the synthesized polycarboxylate superplasticizer in concrete mixtures were measured according to ASTM C49438. The slump values for concrete mixtures were controlled within the range of 200 ± 15 mm. The difference in water consumption between the concrete mixture without the superplasticizer and those with added superplasticizers was studied to calculate the percentage reduction in water for the superplasticizer used in the concrete.
Workability Retention. The workability of the concrete mixture with the superplasticizer was tested using the slump cone method, after which the cone was slowly raised vertically. The initial flow of the concrete mixture was assessed as the difference between the height of the cone and the highest point of the sample. This analysis was conducted in accordance with the testing method of GOST 26798.1-96. The ability to retain fluidity was evaluated by measuring the change in slump of the concrete mixture at intervals of 30, 60, and 90 minutes. It should be noted that each concrete sample was re-mixed for 20 seconds before analysis.
Results and Discussion. The synthesized polycarboxylate superplasticizer was analyzed using IR spectroscopy on an "IR Tracer-100" spectrometer (SHIMADZU CORP., Japan, 2017). The high sensitivity of the spectrometer (signal-to-noise ratio of 60000:1) allows for the analysis of the wave amounts in various samples despite the low intensity of the spectral ranges, with the wavelength range being 3398.57 to 603.72 cm-1.
In Figure 2, the broad peaks between 3300 cm^ and 3500 cm^ are attributed to the stretching vibrations of the O-H groups. Peaks at 2883 cm\ 1647 cm\ and 1348 cm^ correspond to the characteristic absorption zones of polyethylene oxide (CH2CH2O) groups. The typical absorption peak for the stretching vibrations of the C-O-C structure was found at 1083 cm1 The characteristic absorption peak of the COO group appeared at 1456 cm1 The absence of resonance
for the carbonyl bond in AA and TPEG is the reason for the observed shift toward higher wavenumbers. Thus, the vibrational signals observed in the IR spectra confirm that the polycarboxylate superplasticizer has been successfully synthesized.
Figure 2. IR Spectral Analysis of Polycarboxylate Superplasticizer.
The compressive and flexural strengths of concrete mixtures prepared by adding various amounts of polycarboxylate superplasticizer were studied over different time periods. Figure 2 shows the compressive strengths of concrete samples with various amounts of polycarboxylate superplasticizer (0.2%, 0.4%, 0.6%, 0.8%) after 3, 7, and 28 days. The study of the mechanical properties of the concrete with the polycarboxylate superplasticizer indicates that the compressive strength is dependent on the concentration of the superplasticizer. As the weight of the concrete samples increases, the compressive strength of the concrete sample follows an increasing trend (Figure 2).
Figure 2. Strength of Concrete with Polycarboxylate Superplasticizer.
The hardening period of the concrete improves from 3 days to 7 and 28 days, which is attributed to the good dispersion of the polycarboxylate superplasticizer among the cement particles. By adding the superplasticizer to the concrete mixture, the demand for water decreases, leading to an increase in the strength of the concrete. During the hardening periods of 7 and 28 days, the improvement in the strength of the concrete became significant with an increase in the
amount of polycarboxylate. After 3, 7, and 28 days of hardening, the concrete samples with 0.8% polycarboxylate superplasticizer exhibited compressive strengths of 31.3, 42.1, and 55.5 MPa, respectively. The strength of the concrete with the superplasticizer shows a faster improvement compared to the concrete samples without additives over the same period from 3 to 28 days.
Figure 3. Flexural Strength of Concrete with Polycarboxylate Superplasticizer.
The flexural strength of concrete mixtures with various amounts of polycarboxylate superplasticizer was studied through analysis during the hardening periods of 3, 7, and 28 days. In Figure 3, the dynamics of changes in the flexural strength of the concrete samples with the superplasticizer correspond to their amounts. As the amount of superplasticizer increases, it has a significant impact on the flexural strength of the concrete samples produced during the hardening period. The flexural strength of concrete samples with 0.2% to 0.8% superplasticizer improved by 20-72%, 21-88%, and 22-100%, respectively, after 3, 7, and 28 days of hardening. Additionally, it was found that the concrete samples containing polycarboxylate exhibited higher flexural strength compared to the concrete without the superplasticizer after 3, 7, and 28 days. The results of the flexural strength tests correspond to the results of the compressive strength tests. Adding more than 0.8% superplasticizer to the concrete leads to a decrease in strength. However, it reduces water consumption and contributes to the improvement of mechanical properties.
Conclusion.
The polycarboxylate superplasticizer was synthesized primarily based on TPEG-2400 and acrylic acid. According to the analysis obtained from IR spectroscopy, the acrylic acid monomer was successfully polymerized into polycarboxylate molecules. The characteristic bands in the IR spectra indicate that the composition of the concrete with added polycarboxylate superplasticizers contains more distinctive features compared to the concrete samples without additives, leading to an increase in the strength of the concrete samples. The results demonstrate that the quality of concrete products improves with the addition of superplasticizers. The effects of adding superplasticizer at 0.2% to 0.8% relative to the mass of cement in the concrete mixture were studied. The increase in the strength of the concrete samples was achieved by improving the porous structure through the addition of the superplasticizer. It was proven that adding more than 1% of the synthesized polycarboxylate superplasticizer to the concrete mixture is not beneficial. The dispersion of the cement paste was studied in accordance with GOST 26798.1-96 [20].
REFERENCES
1. Ismoilov F.S., Karimov M.U., Djalilov A.T. Study of the Influence of the Obtained Superplasticizer and Its Effect on the Physical-Chemical and Physical-Mechanical Properties of Cement Compositions through IR Spectra. / Scientific-Technical Journal of FerPI. / ISSN 2181-7200. Fergana - 2023. pp. 94-99.
2. Sha, S., Wang, M., Shi, C. & Xiao, Y. Influence of the structures of polycarboxylate superplasticizer on its performance in cement-based materials-a review. Constr. Build. Mater. 233, 117257 (2020).
3. Yuan, Y. et al. Mathematical models of apparent viscosity as a function of water-cement binder ratio and superplasticizer in cement pastes. Sci. Rep. 13, 22301 (2023).
4. Sheikh Hassani, M., Torki, A., Asadollahfardi, G., Saghravani, S. F. & Shafaei, J. The effect of water to cement ratio and age on the mechanical properties of cement mortar and concrete made of micro nano bubbles without adding any admixtures. Struct. Concr. 22, E756-E768 (2021).
5. Sujitha, V. S., Ramesh, B. & Xavier, J. R. Effect of superabsorbent polymer hydrogels in the advancement of cementitious materials A review. J. Polym. Environ. 31, 2761-2778 (2023).
6. Zhang, K., Mezhov, A. & Schmidt, W. Effect of polycarboxylate superplasticizer in ordinary Portland cement and sulfate resistant cement. J. Mater. Civ. Eng. 35, 04023113 (2023).
7. Ma, R., Wang, Y., Li, H. & Bai, Y. Progress in the polycarboxylate superplasticizer and their structure-activity relationship—A review. Mater. Today Commun. 35, 105838 (2023).
8. Ezzat, M. et al. Novel concrete superplasticizers with sterically hindered amines as stabilizing pendant side chains. Eur. Polym. J.196, 112301 (2023).
9. Ma, Y. et al. Adsorption and dispersion capability of polycarboxylate-based superplasticizers: A review. J. Sustain. Cem. Mater. 11, 319-344 (2022).
10. Lai, G. et al. A mechanistic study on the effectiveness of star-like and comb-like polycarboxylate superplasticizers in cement pastes. Cem. Concr. Res. 175, 107389 (2024).
11. Xia, Y. et al. Synthesis and modification of polycarboxylate superplasticizers—A review. Materials 17, 1092 (2024).
12. Li, Y. et al. Study on dispersion, adsorption and flow retaining behaviors of cement mortars with TPEG-type polyether kind polycarboxylate superplasticizers. Constr. Build. Mater. 64, 324-332 (2014).
13. Li, S. et al. Synthesis and performance of a novel amphoteric polycarboxylate superplasticizer with hydrolysable ester group. Coll. Surf. A Physicochem. Eng. Asp. 564, 78-88 (2019).
14. Zhu, W. et al. Effect of a specific PCE superplasticizer on the initial dissolution and early hydration of Portland cement. J. Build. Eng. 46, 103786 (2022).
15. Yang, J., Li, G., Yang, W. & Guan, J. Effect of polycarboxylic grinding aid on cement chemistry and properties. Polymers 14, 3905 (2022).
16. Kwasny, J.; Sonebi, M.; Plasse, J.; Amziane, S. Influence of rheology on the quality of surface finish of cement-based mortars. Constr. Build. Mater. 2015, 89, 102-109. [CrossRef]
17. Liu, B.; Wang, L.G.; Pan, G.H.; Li, D.X. Dispersion of graphene oxide modified polycarboxylate superplasticizer in cement alkali solution for improving cement composites. J. Build. 2022, 57, 104860. [CrossRef]
18. Mardani-Aghabaglou, A.; Tuyan, M.; Yilmaz, G.; Ariöz, Ö.; Ramyar, K. Effect of different types of superplasticizer on fresh, rheological and strength properties of self-consolidating concrete. Constr. Build. Mater. 2013, 47, 1020-1025. [CrossRef]
19. Gao, Y.; Tian, W.; Li, Y.; Zhu, J.; Liao, M.; Xie, Y. Study on compatibility mechanism of plasticizer and asphalt based on molecular dynamics. Mater. Des. 2023, 228, 111827. [CrossRef].
20. Ismoilov F.S. Development of Technology for Obtaining Superplasticizers for Concrete Mixtures Based on Pyrolysis Oil and Their Application. // Dissertation. Tashkent, 2023.
