With the rapid development of construction, the quality requirements for engineering construction continue to increase, which requires continuous improvement of concrete properties and the purpose of saving energy. The use of admixtures in concrete improves the performance of concrete. When using admixtures, the dosage must be controlled, otherwise the compressive strength of the concrete will be reduced and the safety of the project will be affected.
In order to improve the properties of fresh concrete, concrete admixtures are generally added before the concrete mixing station or during mixing. Admixtures are auxiliary materials that improve the performance of concrete. Their effects vary by type. Generally, the functions of admixtures, high-efficiency water-reducing agents and performance water-reducing agents have the following aspects: they can effectively improve the performance of fresh concrete. Easy pouring and cohesiveness; save the amount of concrete used, when the slump of concrete is required, because the use of admixtures can better improve its strength and reduce costs; improve the performance of concrete, in the use of concrete When the amount and concrete slump are required, admixtures can greatly improve the performance of concrete, thereby increasing the strength of concrete and extending the service life of the building; improving the fluidity of concrete, the application of admixtures can be used in concrete and concrete When water is needed, it can effectively improve its fluidity, make the concrete easier to mix evenly, and make pouring construction more convenient.
Concrete water-reducing agent is mainly composed of anionic surfactants. When added to concrete, the melting effect of fresh concrete increases, thereby improving the properties of the concrete. Compared with traditional concrete, adding admixtures makes the concrete have dispersion, lubrication and steric hindrance effects. Analysis of the harm of adding admixtures to concrete properties.
① Concrete lifting admixtures can reduce its bleeding rate. Because of the application of admixtures, the concrete water-cement ratio is reduced, thereby reducing the bleeding rate and improving the dispersion of concrete.
② Adding admixtures to concrete can improve its fluidity. The slump value is a criterion for measuring the fluidity of concrete. It has been found through experiments that when water and concrete are used for mixing concrete, admixtures can increase the slump value, that is, improve its fluidity.
③ Adding admixtures to concrete can increase its air content. Not only air-entraining agents, general admixtures can also increase the air content of concrete.
④ Adding admixtures to concrete can reduce corrosion of building steel bars. Because admixtures can reduce the demand for water, thereby reducing the water-cement ratio of concrete and improving the corrosion resistance of building steel bars.
For example, when the air-entraining agent is in a concrete mixing plant, it contains a large number of fine stable bubbles, which improves the stability and adhesion of the concrete. To sum up, air-entraining agents have very good effects in three aspects: foaming, foam stabilization, and page specificity. The main effects of air-entraining agents on improving the performance of concrete include the following points:
① Adding air-entraining agents to concrete can improve its adhesion. With the addition of air-entraining agent, a large number of stable bubbles are included inside the concrete, which reduces the segregation of bleeding concrete when the concrete is used, and also increases the slump of the concrete. In this sense, it It is the result of improved concrete adhesion.
②The harm of adding air-entraining agent to concrete to its setting time. Under normal circumstances, adding or not using air-entraining agents has little impact on the concrete setting time.
③ Adding air-entraining agents to concrete has an impact on its performance, because air-entraining agents can significantly reduce the surface tension and page energy of water, making it easy for the solution to cause many tiny closed structures during the mixing process. At the same time, the molecules of the air-entraining agent are directionally adsorbed on the surface of the bubbles, forming a relatively strong liquid film, which makes the bubbles stable and not easy to break. Under the action of such stable bubbles, the concrete has stronger impermeability. Grade, cold resistance, crack resistance and other properties, thereby improving the performance of concrete.
④The effect of adding air-entraining agent to concrete on its compressive strength. This effect can be demonstrated from two aspects: not only, the water-reducing effect of the air-entraining agent reduces the water-cement ratio of concrete and increases its compressive strength; at the same time, the use of air-entraining agents makes the concrete contain many Vapor reduces the density of concrete, which in turn reduces the compressive strength of concrete. Therefore, the harm of air-entraining agents to the strength of concrete must be viewed from these two levels. Experiments have found that due to the presence of air bubbles in concrete, the elastic mold of the concrete building parts is reduced, which also reduces the strength of the concrete. This reduction in compressive strength does not offset its improvement effect and reduces the overall compressive strength of concrete.
Due to the wide variety of admixtures, appropriate admixtures must be selected based on the characteristics of the project and the main purpose of the concrete. The standard is not only to consider the design plan and construction, but also to be economically effective. The following is a detailed description of the selection of concrete admixtures that are currently used more frequently:
① Modified material naphthalene series admixtures. Because this type of addition�It can improve the solidification and heating capacity of concrete and can be used as equipment for large-volume concrete. During the installation and construction of large-volume concrete, a large amount of hydration heat will be generated, which is not conducive to construction, and these two admixtures can effectively weaken the thermoelectric effect;
②Polysulfamate Admixtures and air-entraining agents. Because of its ability to reduce work, this type of admixture can be well used in the preparation of durable concrete;
③Polysulfamate concrete admixtures can be used as high-strength concrete admixtures due to their large water reduction rates. Concrete, while polysulfamate concrete admixtures can improve the pumpability of concrete and can be equipped with concrete pumping to reduce the re-absorption of concrete during transportation and reduce slump damage.
The dosage of admixtures will affect the quality of concrete. Too much or too little will not play its role optimally. Therefore, it is necessary to carry out configuration tests on admixtures to determine their dosage. Use commonly used raw materials in construction to conduct concrete mix proportion tests to find the best parameter range of admixtures, and finally determine the intake amount based on economic development standards. </p
微信扫一扫打赏
