Jiangsu Concrete Anti-Segregation Agent Manufacturer-What are the reasons for cement segregation in concrete?

Contents of this article

• The best formula for concrete anti-segregation agent?

• What are the main ingredients of the water reducing agent used in concrete?

• What are the main ingredients of cement superplasticizer?

• How to remedy bleeding when pouring?

• What are the reasons for cement segregation in concrete?

• After the water-reducing agent is added to the concrete, it turns black. Is it segregated?

What is the best formula for concrete anti-segregation agent?

Concrete, as the largest building material, has developed rapidly. In recent years, high-strength and high-performance concrete has been widely used in engineering. The fluidity of concrete has developed from the previous 70~90mm to the current slump of 180~230mm. Some projects also use self-compacting concrete, and the pumping height is getting higher and higher. However, the fluidity and cohesion of concrete are often incompatible, that is, it is difficult for concrete to maintain high cohesion properties under large flow conditions. In this way, concrete that pursues high fluidity is prone to bleeding and segregation. Moreover, with the gradual depletion of river sand resources and mineral resources in my country, the gradation and fineness of river sand fluctuate greatly, ordinary manufactured sand with poor particle size is used on a large scale, the water retention of cement fluctuates, and high water reduction but The more sensitive polycarboxylic acid-type water-reducing admixtures are constantly being promoted, and the quality control of ready-mixed concrete is facing increasingly severe challenges. The existing concrete anti-segregation agents have a strong flocculation effect, which will cause the concrete to settle quickly and the concrete to lose its flow properties instantly, which is detrimental to the workability of concrete. For this reason, we propose an anti-segregation agent for concrete and its preparation method.

Technical implementation elements:

The purpose of the present invention is to provide an anti-segregation agent for concrete and a preparation method thereof to solve the existing concrete anti-segregation problems proposed in the above background technology. The strong flocculation effect of the agent will cause the concrete to settle quickly, causing the concrete to lose its flow properties instantly, which is detrimental to the workability of the concrete.

In order to achieve the above object, the present invention provides the following technical solution: an anti-segregation agent for concrete, the composition of the anti-segregation agent for concrete is as follows:

Fly ash 5- 15 parts, mineral powder 5-15 parts, steel fiber 1-2 parts, polyethylene glycol 1-2 parts, polyhydroxy acid water reducing agent 20-30 parts, tackifier 0.8-1.2 parts, coagulant 0.5- 0.9 parts, 200-300 parts of deionized water, several parts of liquid alkali, 5-10 parts of silicone monomer, 3-5 parts of oxidizing agent, and 1-3 parts of reducing agent.

Preferably, the organosilicon monomer is propyltrichlorosilane or vinyltrichlorosilane or fluorosilicone monomer or a mixture of the three.

Preferably, the coagulant is powdered sodium sulfate.

Preferably, the tackifier is PAM, and the PAM is moistened with methanol or ethanol, deionized water is added for stirring, and the mixture is heated to 55 degrees Celsius during stirring to prepare a solution with a concentration of 4%.

Preferably, the oxidizing agent is one or a mixture of hydrogen peroxide, ammonium persulfate, and potassium persulfate.

Preferably, the reducing agent is ammonium persulfate-anhydrous sodium bisulfite or ammonium persulfate-sodium hypophosphite.

Preferably, the alkali solution is sodium hydroxide.

Preferably, the preparation method of the concrete anti-segregation agent includes the following steps:

S1: Mixing: combine silicone monomer, deionized water, polyhydroxyacid water-reducing agent and polyethylene glycol are added into the reaction kettle for mixing;

S2: Oxidation: Stir until the mixture in step S1 is evenly mixed, and add oxidant for oxidation;

S3: Reduction: Add fly ash, mineral powder and steel fiber to the oxidized mixture in step S2, and then add the reducing agent;

S4: Neutralization: Add a tackifier to the reduced mixture in step S3 and coagulant, stir continuously until the mixture is uniform, and then add liquid caustic soda to adjust the pH so that the pH is between 7-9, and then the anti-segregation agent for concrete can be obtained.

Compared with the existing technology, the beneficial effects of the present invention are: the invention adds fly ash, mineral powder and steel fiber to the anti-segregation agent, which can not only improve the compressive strength of concrete, but also It can also effectively improve the working performance and stratification of concrete, improve the segregation resistance of concrete, and reduce the expansion and slump of concrete. PAM is used as a tackifier because PAM has more -NH2. The tackifier has good hydrophilicity, making the concrete hydrophilic, water-retaining, thickening, resistance-reducing and viscosity-increasing. Adding calcium sulfate as a setting accelerator can promote concrete water splashing, accelerate hardening, and promote condensation. The invention has wide sources of raw materials, low cost, green and environmental protection, and simple operation.

What are the main ingredients of the water reducing agent used in concrete?

The water reduction rate of pulp waste liquid, the main component of sodium lignosulfonate, is 10% to 15%; the 28d strength is increased by 10% to 20%; the slump is increased by 100 to 150㎜ 0.2 to 0.3 MY type reducer The main component of the water agent is lignocalcium derivatives, pH 8 ~ 9, powdery water reducing rate 9% ~ 12%; 3d and 28d strength increased by 15%; air entrainment capacity 3% ~ 4% 0.2 ~ 0.3 GF-G type water reducing agent mainly Ingredients: Magnesium lignosulfonate water reduction rate is 8%; 3d and 28d strength increased by 12% 0.4

What are the main ingredients of cement water-reducing agent?

Water reducing agent is an admixture that can reduce the necessary unit water consumption in concrete, meet the specified consistency requirements, and improve the workability of concrete. The main functions of water reducing agents are as follows: increasing hydration efficiency, reducing unit water consumption, increasing strength, saving cement consumption; improving the workability of concrete that has not yet solidified, and preventing concrete composition��aggregate with each other into larger particles, which reduces the surface energy of the cement particles and weakens the adsorption of the water-reducing agent by the cement particles. During the concrete test, the water-reducing effect of the water-reducing agent is often enhanced, and the new concrete mixture appears to ooze slurry. The phenomenon of grabbing the bottom. In actual production, if cement stored for a long time is used, even if the concrete mix ratio is the same as before (concrete had good workability when produced with this ratio in the past), it may cause segregation of concrete. Of course, the storage time of cement has different effects on different varieties. The effect of cement is inconsistent and needs to be understood through experiments. The storage time of cement will cause obvious changes in the adaptability of cement and admixtures. Especially when doing trial mixing of concrete mix proportions, special attention should be paid to the consistency between the cement samples during the trial mixing and the batch supply of cement. This can effectively ensure the feasibility of the trial mixing work. During the production process, if the cement is stored for too long, it is best to conduct adaptability tests on the cement and admixtures to re-determine the reasonable dosage of admixtures to ensure good workability of the concrete. Most of the admixtures used in concrete are multifunctional products composed of water-reducing agents and other compounds such as air-entraining agents, retarders, plastic retainers, etc. They are indispensable and important materials for pumping concrete. The mixing of admixtures The addition of admixtures can greatly improve the performance of concrete mixtures (fresh performance and long-term performance), but improper use of admixtures may lead to segregation of concrete. (1) If the amount of concrete water-reducing agent is too large, the water-reducing rate is too high, and the water consumption of a single concrete is reduced, it is possible that the water-reducing agent will not fully play its role in the mixer, and continuous occurrences will occur during the concrete transportation process. The effect causes the slump of the concrete to the site to be greater than the slump when it leaves the machine.

This situation can easily cause serious segregation of concrete. And it often appears in high-strength grade concrete, which is extremely harmful to concrete. (2) Excessive amounts of retarding components and plastic-preserving components of admixtures, especially excessive amounts of phosphates or sugars, can easily cause segregation in concrete.

Fly ash is one of the important admixtures in concrete. The microbead effect, filling effect and volcanic ash effect of fly ash in concrete greatly improve the workability, compactness and strength properties of concrete. .

High-quality fly ash is an ideal material for preparing concrete. It can replace 10% to 30% of cement, greatly reducing the cost of concrete production. However, the supply of fly ash on the market is now tight, and most manufacturers cannot guarantee the quality of fly ash. The quality of fly ash fluctuates greatly, which increases the difficulty of concrete quality control and sometimes causes segregation of concrete. Sand and gravel are the most commonly used materials in concrete. The quality of sand and gravel directly affects the quality of concrete. Fluctuations in the quality of sand and gravel can easily cause segregation of concrete, and there are many factors that cause segregation. (1) The increase in gravel particle size, deterioration of gradation, and single gradation can easily cause the segregation of concrete. (2) Excessive stone content in sand, especially excessive flake stone chips, will seriously affect the workability of concrete and lead to serious segregation of concrete. (3) The moisture content of sand and gravel is too high (especially the moisture content of sand is too high, greater than 10%), which will make it difficult to control the quality of concrete and prone to concrete segregation. Because the water content in the sand is too large and is in a supersaturated state, when the concrete mixture is mixed in the mixer, the water in the capillary tubes on the surface of the sand cannot be released in time, so it is easy to use too much mixing water during mixing; at the same time During the transportation of concrete, the water in the capillary tubes of the aggregate is continuously released, destroying the bond between the aggregate and the cement slurry, causing segregation and bleeding of the concrete. (4) Excessive mud content in sand and gravel will reduce the bonding force between the cement slurry and the aggregate, and the cement slurry’s ability to wrap the aggregate will decrease, leading to the separation of the aggregate and causing concrete segregation. Adding a certain amount of mineral admixtures into concrete can, on the one hand, improve the various properties of the concrete, and on the other hand, it can achieve good economic benefits. Therefore, the use of mineral admixtures is very common in various concrete mixing stations, such as: slag powder, steel slag powder, silica powder, zeolite powder, etc. Various mineral admixtures have different effects on concrete segregation. Silica fume and zeolite powder have strong ability to resist the segregation of concrete and can greatly improve the workability of concrete. Due to its large specific gravity, steel slag powder can increase the density of mortar after being added, which is helpful to improve the workability of concrete. The incorporation of slag powder increases the viscosity of concrete to a certain extent, and concrete is prone to segregation. The degree of influence is closely related to the fineness of slag powder. Generally, the higher the fineness, the better the resistance to concrete segregation

After the water-reducing agent is added to the concrete, it turns black. Is it segregated?

Not segregation. Blackening: It is caused by the floating of admixtures such as coal ash and mineral powder, which causes patches of blackening of the slurry on the surface of the concrete. Segregation of concrete is a phenomenon in which the cohesion between the components of the concrete mixture is insufficient to resist the sinking of the coarse aggregate, and the components of the concrete mixture separate from each other, resulting in uneven internal composition and structure.

Usually manifested as the separation of coarse aggregate and mortar from each other, for example, dense particles are deposited at the bottom of the mixture, or coarse aggregate is separated from the mixture as a whole.

<img src="/upfile/202304/2023041334528065.jpg"/