Concrete water-reducing agent, as the sixth component of concrete, is a necessary component to enhance and improve the properties of concrete. Polycarboxylate-based water-reducing agent is characterized by its low dosage and With high water reducing rate, low slump damage, environmental protection and ion energy regulation, it has become the preferred water reducing agent for various large and medium-sized construction projects or key parts.
At present, the demand for Korean polycarboxylic acid superplasticizers in concrete has accounted for about 90%. In China, the production and sales of polycarboxylic acid-based water-reducing agents are still relatively small compared to naphthalene-based water-reducing agents. However, the water-reducing rate of naphthalene-based water-reducing agents is low, and the configured concrete has large slump damage, which has many shortcomings in application. Therefore, the demand for polycarboxylic acid-based water-reducing agents will become greater and greater. At present, many companies in China have produced polycarboxylic acid-based water-reducing agents, and their properties are already comparable to those of well-known overseas brands. similar. Therefore, the research on polycarboxylic acid water-reducing agents is gaining more and more attention. This article conducts experiments by selecting several mother solutions of polycarboxylic acid-based water-reducing agents sold on the market around the world, making a necessary comparison of the properties of the current polycarboxylic acid-based water-reducing agents, and grasping the current water-reducing properties on the market. The application status of the polycarboxylic acid-based water-reducing agent was discussed, and the working principle of the polycarboxylic acid-based water-reducing agent was discussed, providing necessary training plans for the subsequent production and development of polycarboxylic acid-based water-reducing agents.
Raw materials
⑴Concrete: Dongyue brand P.Ⅱ42 produced by Jiangsu Chemical Plant. 9 concrete.
⑵ Water-reducing agent: Choose several pure mother solutions of polycarboxylic acid-based water-reducing agents on the market (all dosages in the manuscript are liquid Dosage), all are transparent liquids with a solid content of 20% (the names of water-reducing agents below are replaced by numbers).
A: Catalyst water-reducing agent produced by Korean catalyst company.
B: ADVA152DL water reducing agent produced by Grace Enterprises.
C: KJ-JS superplasticizer produced by Kejie superplasticizer company.
⑶ Sand: ISO standard sand, produced by Fuzhou ISO standard sand company.
Experimental method
⑴Cement slurry swimming degree experiment: cement slurry swimming The experiment was carried out with reference to the relevant requirements of "Experimental Method for Homogeneity of Concrete Admixtures" (GB/T8077-2000).
(2) Mortar air content: The mortar air content shall be tested with reference to the relevant requirements of the "Specification for Experimental Methods for the Characteristics of Foundation Mortars in Housing Construction" (JGJ/T70-2009).
(3) Mortar strength: Concrete mortar strength was tested with reference to "Concrete Mortar Strength Testing Method" GB/T 17671-1999.
The working properties of concrete are mainly controlled by its fluidity, and the fluidity is mainly determined by the refinement of concrete particles. There is no doubt that one of the most important functions of water reducing agents is to make concrete have stronger fluidity. Figure 1 also shows the fluidity and mobility maintenance status of cement slurry after adding various polycarboxylic acid-based water reducing agents. It can be seen from Figure 1 that after adding various types of water-reducing agents, the mobility of the cement slurry increases rapidly with the increase in the amount of water-reducing agents, and then the slope of the fold line decreases and the growth rate slows down. The water-reducing agent content continues to rise after it exceeds the necessary dosage (usually around 0.2%). Moreover, after adding water-reducing agent, the expansion degree of the cement slurry exceeds about 300mm, and the phenomenon of secret water is unlikely to occur.
The change in swimming degree of the specimen after immersion is similar to that of the original swimming degree. They all expand rapidly at first, then slow down, and finally tend to be gentle. , and the distance between the swimming fold line and the original fold line of each test piece after 30 minutes is very close, which also means that the fluidity maintenance potential of various types of water-reducing agents is strong, and most of them are not damaged within half an hour. This characteristic of polycarboxylic acid-based water-reducing agents is unmatched by other water-reducing agents at this stage, which is why this type of water-reducing agent has received a lot of attention. Polycarboxylic acid water-reducing agent often has such a good effect, the key is to analyze it from its molecular formula. The molecular formula arrangement of the polycarboxylic acid-based water reducing agent is to generate side chains on the ion main chain, and introduce strong chemical groups on the side chains, such as carboxyl groups, sulfonic acid groups, polyoxyethylene groups, etc., so that the ions have a comb-type Structure [2 (shown in ] 3), by adjusting the proportion of chemical properties or non-chemical properties, adjusting the content, adding various functional ability groups, etc., to grant new properties to the water-reducing agent. This type of water-reducing agent ions have a "comb-type" structure. When adsorbed on the surface of concrete particles, the strong chemical properties of the polycarboxylic acid-based water-reducing agent ion main chain ionize a small part of the steel bars and overlap the surface of the concrete particles, forming a Ring adsorption. Its side chains extend into the liquid phase, thus providing significant steric repulsion between concrete particles; at the same time, the main chain contains many hydrophilic specific groups (such as -OH, -COOH, etc.), which make concrete The interaction between particles and water increases, the etherification effect of oil on the surface of concrete particles increases, and the hydration film becomes thicker. Therefore, this type of water-reducing agent has a strong hydration film lubrication and water-reducing effect. Because the polycarboxylic acid water-reducing agent ions contain many hydroxyl groups (-OH), ether groups (-O-) and carboxyl groups (-COOH), this chemical group has extremely strong "liquid-gas" page specificity , so thisThe water-reducing agent also has a certain air entrainment protection "steel ball" water-reducing effect. Therefore, the polycarboxylic acid water-reducing agent has stronger refining and water-reducing potential and stronger refining effect.
</p
微信扫一扫打赏
