With the continuous construction and development of construction projects, concrete as one of the most basic building construction materials, its performance will have a certain impact on the construction quality of the entire construction project. Only by adding water reducing agent inside the concrete can the quality performance of the concrete be effectively improved. However, the most critical thing is to grasp the content of water reducing agent.
The amount of superplasticizer will have a great impact on the quality and performance of concrete, so it is necessary to strengthen the control of the amount of superplasticizer from the microscopic point of view, so as to improve the quality and performance of concrete.
The performance and effect analysis of PCE water-reducing agent
The water-reducing agent, also known as a dispersant, is an external additive utilized in the preparation of raw materials for engineering construction. It is employed in concrete preparation to maintain optimal workability and effectively regulate water consumption. As a surfactant, it enhances the surface activity of concrete. By controlling the water content in the mixture, the water-reducing agent significantly improves the strength, durability, and permeability of concrete while optimizing its overall performance. This additive ensures high-quality raw materials that meet mechanized construction standards, reduces construction noise levels, and minimizes cement usage. Cement particles are granular materials with diameters typically ranging from 7 to 80 microns; they possess fine textures resembling powder particles. These cement particles exhibit strong hydrophilicity due to their polar surfaces and have a large specific surface energy.
Concrete water reducing agents can ensure that the water consumption is controlled on the basis of ensuring the workability of concrete, and can also improve the workability of concrete on the premise of controlling the water consumption. Specific types of water reducing agents include: ordinary water reducing agents and high efficiency water reducing agents. Among them, the ordinary type of water reducing agent generally has a water reducing rate of more than 5%, the general concrete time reaches one week, its compressive strength can be increased by 10%, the time is one month, its compressive strength can be increased by 5%, the high efficiency water reducing agent can control the water consumption in a wide range to ensure that the concrete is in a state of high-speed flow, the water reducing rate should be above 10%, the age of 3 days of concrete, Its compressive strength can be increased by 25%.
The most significant characteristics of ultra-high strength concrete are: large fluidity, low water-cement ratio, which requires the addition of highly efficient water reducing agent, or the use of over-mixing method, however, which must pay attention to the control of the content, pay attention to grasp the proportion of the content, in order to improve the performance and quality of concrete.
The influence of the amount of high efficiency water reducing agent on the quality performance of concrete
1)Influence of water-reducing agent on compressive strength of concrete
A key mechanical property of concrete is compressive strength, the strength of concrete will affect other properties of concrete, usually the compressive strength of sewage stone will affect the strength of concrete to a certain extent, become a key factor, generally speaking, the porosity of cement stone and density, strength between the following relationship: R=ARC(C/W-B) R -- compressive strength of concrete, A, B -- empirical constant, RC -- cement strength can be obtained with the above formula: The water-cement ratio and hydration degree of cement grout will directly affect the strength of concrete. When water reducing agent is added to the inside of concrete, the water-cement ratio will be greatly reduced, the pores in the cement stone will be significantly reduced, the cement stone will be tight and detailed, and the corresponding compressive strength of concrete will also increase.
2) Effect of water reducing agent on durability of concrete
a) Resistance to freeze-thaw effects
Water-cement ratio and combined gas volume can greatly affect the freeze-thaw resistance of concrete. After investigation, it is concluded that the freeze-thaw resistance of concrete is proportional to its water-cement ratio, and the freeze-thaw resistance of concrete will be optimized and improved by adding water reducing agent in accordance with scientific proportion. There are voids of different sizes and sizes inside the concrete, and the texture and nature of the water inside will also change greatly according to the aperture size. There is a certain relationship between the bubble structure of concrete and the freeze-thaw resistance, and its freeze-thaw resistance will change with the change of the types of admixtures. Generally speaking, if 2% of the gas is injected into the concrete, its durability can be properly optimized and improved, if the exhaust gas is greater than 6%, it may reduce the strength of the concrete, its durability is also affected, the best exhaust gas can be in 2%-5%.
b) Effect on corrosion of steel bar
Reinforced concrete structure is often used in modern engineering construction, and the firmness, stability and durability of steel-concrete structure are related to the carbonization of concrete to a certain extent. Because the air contains a large amount of carbon dioxide, the gas will form a corrosive effect on the concrete, causing the calcium hydroxide inside the concrete to gradually evolve into calcium carbonate, thereby losing its alkalinity. Once carbon dioxide gradually penetrates into the local steel bar, the passivation film may be corroded over time, and the corresponding steel bar will also be chemically corroded. Even if the admixture is added and contains a certain amount of Cl-, the concrete with water reducing agent can effectively control the carbonization rate, so as to achieve the height, standard and quality of cement carbonization resistance, and the degree of corrosion of concrete reinforcement is significantly controlled, so that the corrosion resistance of steel reinforcement can be optimized, and concrete can be used for a long time.
c) Effect of impermeability
There is a certain relationship between water-cement ratio and impermeability, water-cement ratio > 0.55. Because the water consumption of concrete mixing will greatly exceed the water amount of cement hydration, there will be a certain amount of residual hydration water inside the concrete, and the pores inside the concrete can enhance the permeability of the concrete. However, when the water-cement ratio is too low to reach the expected workability, the concrete structure may be damaged and the impermeability will also be affected.
The influence of water-reducing agent on the workability of concrete
Concrete workability will be affected by multiple factors, such as: cement, water, and the amount of admixtures used, temperature and properties, ordinary factors are not much different, the type of water reducing agent, the amount of water reducing agent will affect the workability of concrete. Slump value is generally used as a measure of workability, however, slump is proportional to the amount of water reducer used, generally as follows: Water reducing agent content =0.5% cement content, slump becomes larger, if the water reducing agent content is greater than 0.5% cement content, slump is greatly reduced, the conventional amount of water reducing agent is generally to 0.25% of the proportion, the amount of incorporation should not be too large, may aggravate solidification, generally for high efficiency water reducing agent, then usually choose 0.50%-0.75% of the proportion.
Effect on concrete setting time
Concrete construction will be carried out with great reference to the setting time in actual engineering construction, and the setting time of concrete can be effectively controlled by filling retarder moderately. When the water-reducing agent is used beyond the specific amount of incorporation, the setting time of concrete may be affected, and even non-setting phenomenon may occur. Moreover, due to the rise in temperature, the hydration reaction of cement is also highly efficient, and the speed of setting and hardening is also affected.
5. Influence on rheological properties of concrete
In order to obtain high-quality concrete, it is necessary to deconstruct the viscous structure to ensure that the cement particles can be thoroughly dispersed in the water medium. The cement melting may be affected by a variety of factors. If a certain amount of water reducing agent is added to the newly blended concrete, the charge in the cement particles will rise, and the repulsive force between the cement particles will continue to rise, which will affect its viscosity. Thus, the stability of the dispersion system is enhanced, and the fluidity of the concrete is optimized. The cement slurry mainly includes several states: dilution state, condensation state, and thixotropic state located between two sides. The reason for this state is that the condensed structure in the cement slurry may be continuously separated and decomposed, which is actually reflected in: The shear speed increases, the corresponding resistance, viscosity decreases, according to a specific proportion of water reducer into the cement slurry, can stimulate the concrete stronger thixotropic characteristics, this problem is mainly because the cement is granular, has a certain adsorption function, the corresponding potential will also rise. The increase of vibration will have a certain fluidity, on the contrary, if the concrete is not filled with water reducer, its thixotropy will gradually decrease.
Summary
High efficiency superplasticizer can effectively optimize and adjust the performance of concrete, improve concrete strength, quality grade, durability, etc., reduce the cost of cement addition, and then improve the texture and performance of concrete as a whole, we must correctly select the superplasticizer, scientifically grasp the amount of its inclusion, in order to really play its advantages.
Post time: Jan-11-2024