Does concrete anti-segregation agent have any effect on concrete strength?

Contents of this article

• The best formula for concrete anti-segregation agent?

• What are the effects on the performance of cement concrete after adding retarder?

• Can adding impermeable agent to c30 concrete prevent cracking?

• How to solve concrete bleeding and segregation? What admixtures can be adjusted?

• Does the segregated ash affect the strength?

• Will saving cement with water reducing agent affect the strength?

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 effects of adding retarder on the performance of cement concrete?

1. Retarder is a commonly used admixture used to extend the setting time of concrete. In summer construction, adding an appropriate amount of retarder can make fresh concrete maintain better quality for a long time. Plasticity.

2. Retarder is a surfactant that only plays a physical adsorption and dispersion role in concrete, but does not directly participate in the cement hydration reaction to generate new substances. Therefore, it is suitable for use within a certain dosage range. It has no direct impact on the final strength of concrete, but because it delays the setting time of concrete, it affects the early strength of concrete to a certain extent. However, the later strength can generally catch up with or exceed that of concrete without retarder.

With the rapid development of commercial concrete today, retarder plays a very important role. As people's understanding of retarder continues to deepen, the application of retarder has become more and more important.�� will become more and more widespread, especially when producing large-volume concrete where it is necessary to reduce the instantaneous hydration heat of cement and delay the cement hydration peak, retarders are indispensable.

Can adding anti-penetration agent to c30 concrete prevent cracking?

There is an inseparable dialectical relationship between concrete anti-cracking and anti-permeability, and actual projects cannot deviate from this relation. The establishment of the latest anti-cracking concept of concrete with high permeability and anti-cracking takes advantage of this relationship. After the concrete is poured and formed, the mixing water must not be lost, and perfect wet curing should be used to prevent water loss defects.

This is the only way to follow the laws of concrete development and link the crack resistance and seepage resistance of concrete.

If concrete is allowed to lose water in the early stage of hardening, it will resist cracking but not seepage, which deviates from the inseparable dialectical relationship between crack resistance and seepage resistance. It is the root cause of the common problems of cracking and seepage quality in concrete projects for a long time

How to solve concrete bleeding and segregation? What admixtures can be adjusted?

1. Increase the strength of concrete

After using concrete strengthening agent, the strength of concrete can be increased by 8% to 20%; while the strength remains unchanged, the amount of cement can be reduced 10%～20%.

2.

Improve the performance of concrete

Concrete strengthening agent can effectively improve the workability, bleeding resistance, non-segregation and easy pumping of concrete. And the frost resistance and carbonation resistance have been greatly improved.

3.

Strong adaptability

Not only can it be suitable for various types of concrete and has strong compatibility with various types of admixtures, but it can also improve the The adaptability of carboxylic acid water-reducing agents to raw materials (such as low-quality fly ash, sand with a large mud content, and stones with a large stone powder content) reduces the sensitivity to changes in the dosage of polycarboxylic acid water-reducing agents. It can effectively control the negative phenomena (segregation, poor encapsulation) when the amount of water-reducing agent is high.

4.

Green and environmentally friendly

The potent agent is non-toxic, harmless, non-polluting and non-radioactive, and does not contain chloride ions and alkali.

Does the segregated ash affect the strength?

The strength of segregated concrete will definitely be reduced. The extent of the impact depends on the situation of segregation. To ensure the strength of concrete, its workability and wrapping properties must be good, especially C60 concrete.

Generally speaking, the less water in the concrete, the drier and harder the fresh plastic concrete is and the smaller the slump, the smaller the possibility or tendency of segregation, but it does not necessarily mean that segregation will not occur.

Just after mixing, the sand, stones, cement and water in the concrete are relatively evenly distributed. However, during the transportation and pouring of fresh plastic concrete, due to the different proportions of various materials, the proportion of stones Large particles with large particle sizes are easy to sink, and water with the smallest specific gravity is easy to float, which may cause stratification and segregation, that is, high moisture or even bleeding on the top, and high stone content on the bottom. Especially for high-fluidity concrete, delamination and segregation are very prone to occur during the vibration process.

Will saving cement with water reducing agent affect the strength?

Theoretically, adding a small amount of water-reducing agent will only increase the slump, but will not affect the water-cement ratio and the strength of the concrete.

But if it is not handled properly, it may have a counterproductive effect and will definitely affect the strength.

The addition of water-reducing agent will affect the strength, dry shrinkage and durability of concrete after hardening. First of all, the strength of concrete can be significantly improved, and the strength increase value is related to the water reduction of the water-reducing agent added. The greater the water reduction rate, the more the compressive strength of concrete increases;