PRODUCTION OF SMART SUPERABSORBENT POLYMERS FOR SEALING CRACKS AND INCREASING THE STRENGTH OF CONCRETE STRUCTURES
Dean of the Faculty of Chemistry, Termez State University: B.A. Kholnazarov
E-mail: baxodir.xolnazarov@rambler.ru
Student of the Faculty of Chemistry, Termez State University: Jo‘rayev Ulug‘bek
E-mail: ulugbekjorayev901@gmail.com
Abstract
This scientific work is devoted to studying the production of smart superabsorbent polymers (SAPs) and their integration into concrete mixtures with the aim of solving the problem of cracking in concrete structures and extending their service life. The study analyzes the hydrophilic properties of SAPs, particularly their ability to absorb and retain moisture from the surrounding environment and how this contributes to sealing microcracks and capillary voids within concrete. Furthermore, it demonstrates through practical experiments how the self-healing properties of these polymers enhance the structural integrity and water resistance of concrete.
The paper outlines the synthetic production methods of SAPs, their granulometric composition, chemical stability, and interaction with concrete. The final results serve to improve the long-term durability of concrete products, reduce maintenance costs, and contribute to the development of environmentally friendly innovative building materials. Moreover, SAPs help retain moisture within the concrete, thus supporting the continuation of the cement hydration process.
During the study, various SAP brands, their physicochemical properties, optimal dosages, and methods of integration into concrete mixes were examined experimentally. The results showed a significant improvement in crack resistance, water durability, and strength of concrete samples containing SAPs. This innovative approach enhances the reliability of building materials and extends their service life.
Keywords:
Concrete structures, crack sealing, smart polymers, superabsorbent polymers (SAP), self-healing materials, strength, hydration process, water resistance, innovative construction materials, concrete composition, crack resistance, polymer additives, service life of concrete, construction material innovation, SAP technology, microstructure enhancement, environmentally stable materials, variable humidity conditions, technological additives, mechanical properties of concrete.
Introduction
Today, in the construction industry, requirements such as durability, strength, and long-term performance are of crucial importance. In particular, ensuring the structural stability of concrete constructions remains a pressing issue. Although concrete is one of the most widely used construction materials, it is prone to the formation of internal and external microcracks over time due to various factors. These cracks weaken the structure, lead to corrosion, and shorten the service life of the material.
Therefore, developing technologies that allow concrete to self-heal and automatically seal such cracks is a significant goal. In recent years, smart materials—particularly superabsorbent polymers (SAPs)—have emerged as a promising solution, attracting increasing attention from the scientific and technical communities. These materials can absorb and retain environmental moisture and expand in volume within the concrete to fill cracks as they form. Additionally, by promoting continued cement hydration, SAPs enhance the internal structure of concrete.
This study focuses on producing such SAPs, investigating their properties, and evaluating their practical application in concrete mixtures. Despite the widespread use of concrete, one of its main disadvantages is the development of cracks due to internal pressure, temperature fluctuations, or external loads. These cracks reduce the mechanical strength of concrete and make it more susceptible to external influences, ultimately decreasing structural reliability and increasing repair needs.
Modern construction material technologies offer innovative approaches to solving this issue. In particular, the use of smart materials such as SAPs to develop self-sealing mechanisms in concrete is gaining significant interest. These hydrophilic polymers react with moisture in concrete, expand in volume, and effectively seal cracks. Moreover, they support the continued hydration process of cement, thereby strengthening the internal structure of concrete.
This research provides an in-depth analysis of the use of SAP technology to enhance the strength and crack resistance of concrete.
Materials and Methods
Materials:
In this study, the following materials were used to improve the crack resistance and strength of concrete mixtures:
- Portland Cement (CEM I 42.5N): A high-quality binder and the main component of concrete.
- Natural Sand (0–2 mm): Ensures uniform mass and density of concrete.
- Crushed Stone (5–10 mm): Enhances the mechanical strength of concrete structures.
- Superabsorbent Polymers (SAP): Self-healing polymers that absorb moisture and expand to fill cracks.
- Clean Water: Required for cement hydration and activation of SAPs.
- Plasticizer (polycarboxylate-based): Reduces viscosity of the mix and improves workability.
- SAP Stabilizer (if needed): Controls excessive swelling of SAPs and ensures even distribution in the mix.
Methods:
The following tests and experimental methods were applied to assess the crack resistance and mechanical properties of concrete and to study the effects of SAPs:
- Preparation of Concrete Mix:
Concrete mixes were prepared according to the GOST 10181-2014 standard. SAPs were added in amounts ranging from 0.1% to 0.5% of the cement mass. All samples were prepared under identical conditions using the same components. - Determining Water Absorption Capacity of Polymers:
The water absorption of SAP samples was measured using the gravimetric method: pre-weighed SAP samples were immersed in distilled water for 24 hours, and weight increase was recorded. - Compressive Strength Testing:
The compressive strength of concrete samples was tested at aging intervals of 7, 14, and 28 days following GOST 10180-2012 standards. Each test was conducted three times, and average values were calculated. - Crack Sealing Evaluation:
Pre-cracked concrete samples were stored in a humid environment. The extent to which SAPs sealed the cracks was observed microscopically. Changes in crack width and depth were monitored over 28 days. - Water Resistance and Capillary Absorption Test:
Water permeability of SAP-modified concrete was assessed using a vacuum chamber absorption test. - Microstructure Analysis (Structural Study):
The internal structure of the concrete was analyzed using Scanning Electron Microscopy (SEM) to study the distribution of SAPs and their effect on hydration.
Production of Superabsorbent Polymers (SAPs)
Superabsorbent polymers (SAPs) are hydrophilic polymers capable of absorbing and retaining large amounts of water. These are typically based on acrylic acid and its derivatives and are produced using specific chemical processes. The production process involves the following key stages:
- Monomer Preparation:
The main raw material for SAPs is acrylic acid (CH₂=CHCOOH). It is neutralized using agents such as NaOH, adjusting the pH to the 6–7 range. - Polymerization Process:
The neutralized acrylic acid is mixed with a small amount of cross-linker (e.g., N,N′-methylenebisacrylamide) and an initiator (e.g., ammonium persulfate or sodium persulfate). These components initiate a radical chain polymerization reaction, usually carried out in an aqueous medium at 50–70°C. - Gel Formation:
The resulting polymer forms an elastic gel with a cross-linked structure, capable of absorbing large volumes of water. - Drying:
The fresh SAP gel is dried completely using a vacuum oven or a low-temperature dryer, resulting in a solid yet hydrophilic polymer granule. - Grinding and Sieving:
The dried SAP is ground using a crusher and sieved to achieve the desired particle size (typically 100–800 microns). These granules are then added to concrete mixes. - Quality Control of Finished SAP:
The final SAP product is tested under laboratory conditions for its water absorption capacity, density, swelling recovery, and thermal stability.