One of the factors leading to the deterioration of concrete and reinforced concrete is corrosion caused by electric current. The current effects both structures directly connected to the power source and structures located in the leakage currents zone and stray currents (such as buildings and structures near railway, urban or industrial electric transport). Concrete is a highly heterogeneous material in terms of electrical resistance. The highest resistance is exhibited by aggregates (crushed stone, sand), while the lowest is found in the electrolyte solution within the pores of the cement stone. In the meantime, these values can differ by up to six orders of magnitude. The heterogeneity of reinforced concrete is also evident in the different types of electrical conductivity: electronic conductivity for reinforcement and ionic for concrete.
Electric current is the cause of the electrolysis process, leading to the anodic dissolution of the reinforcement metal. However, reinforcement in concrete is usually in a passive state, and the most severe damage to reinforced concrete is possible under the influence of direct current, the value of which is higher than the critical value (greater than 0.06 A/m2). In reality, only a limited number of reinforced concrete structures are exposed to such currents. The vast majority of structures operate under the influence of stray currents and leakage currents, which are significantly lower in magnitude but persist for longer durations. Under the action of a small in magnitude but long-term potential difference, the processes of ion diffusion occur within the pore solution of cement stone, along with the removal of hydration products and the dissolution of cement’s newly formed compound. This disrupts the ratio of positively and negatively charged surfaces, leads to the development of electrostatic repulsion forces and causes the onset of concrete degradation. Thus, to protect structures from electrocorrosion, concrete must have a certain level of specific electrical resistance to ensure protection under electrical influences. In this case, the purpose of protective methods is to prevent the physicochemical processes in concrete caused by electric current. The most common method involves adding hydrophobic agents to the concrete mix, which seal the pores and prevent ion migration under the influence of potential differences.
As demonstrated in study [1], the introduction of 1% natural latex increased concrete strength and its impermeability to aggressive environments. Two types of polymer latexes were studied in study [2]. Butyl latex, lacking active functional groups on its polymer chains, forms a film on the surface of crystal hydrates and fills cracks and pores in the cement stone. Styrene latex contains active groups that can react with cement hydration products, forming a stronger spatial system. According to authors of study [3], even waste from latex paint improves the processability and durability of concrete while maintaining a satisfactorily low strength of 20 MPa. Using 12 liters of latex paint per 1 m³ of concrete reduced the depth of water penetration by 10%. The modification of cement mortars with small amounts of water-soluble polymers was studied in the research [4]. Using electron microscopy polymer bridges were revealed between layered crystals of Са(ОН)2. This indicates that polymers integrate into the forming cement stone structure, enhancing its strength and water resistance.
As the conducted studies have shown, replacing water for preparing concrete mix with a water-based bitumen emulsion increases the specific electrical resistance of samples by 2.2 times after 28 days of curing. The introduced emulsion slows down strength development process, similar to the effect of plasticizers and water-repelling agents. The acceleration of curing and increasing concrete strength with agents can be achieved through heat and moisture treatment [5].
Thus, the feasibility of producing concrete and reinforced concrete structures with improved electrophysical properties has been demonstrated. Such materials can be used in the production of railway sleepers, improving the insulation resistance of track circuits and enhancing the reliability of transportation processes. Moreover, the manufacturing of other structures from this type of concrete, including foundations, piles, supports, etc., will reduce the impact of leakage and stray currents on the development of electrocorrosion processes in railway transport infrastructure, thereby increasing its durability.
References
1. Remya, V.; Koshy, H. E.: Natural polymer as waterproofing compound in cement concrete, International Journal of Modern Trends in Engineering and Research 3 (2016) 12, Pp. 128-134.
2. Wang, M.; Wang, R.; Yao, H.; Farhan, S.; Zheng, S.; Wang, Z.; et al.: Research on the mechanism of polymer latex modified cement, Construction and Building Materials 111 (2016), Pp. 710–718.
3. Almesfer, N.; Ingham, J.: Effect of waste latex paint on concrete, Cement and Concrete Composites, 46 (2014), Pp. 19–25.
4. Knapen, E.; Van Gemert, D.: Polymer film formation in cement mortars modified with water-soluble polymers, Cement and Concrete Composites 58 (2015), Pp. 23–28.
5. ISO 1920-4:2005 Testing of concrete – Part 4: Strength of hardened concrete.
|
Голосування 
Ця робота ліцензується відповідно до Creative Commons Attribution 4.0 International License
Знайшли помилку? Виділіть помилковий текст мишкою і натисніть Ctrl + Enter