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Will the combination of air entraining agent reduce the strength of concrete?

2022-11-15 13:36:40  Technology

The application of concrete has promoted the rapid development of admixtures and achieved considerable technical, economic and social benefits. 

What is Concrete admixtures?

Concrete admixtures are indispensable for key projects of high-rise buildings, and admixtures have become the fifth indispensable main component in concrete construction. 

According to incomplete statistics, the annual consumption of Chinese and foreign admixtures in commercial concrete has reached millions of tons. 

Because some construction technicians do not have enough understanding and application technology of admixtures, not all of them can achieve better results. In concrete construction, due to improper debugging and application of concrete, admixtures are suspected at first. 

First, the combination of air entraining agent will reduce the strength of concrete? 

The technicians of many concrete construction enterprises think that the mixture of admixtures will reduce the strength of concrete and the air bubbles inside the concrete are caused by admixtures, and the appearance of air bubbles in fresh concrete is caused by air-entraining agents. this is a misunderstanding of air-entraining agent. 

"an increase of 1% air content in concrete will reduce the strength by 3% to 5%" is their theoretical basis. 

It is true that the strength decreases with the increase of air content in concrete, but there is also a premise. It should be exact that when the air content in concrete reaches the fullness value, the strength will decrease when the air content increases. 

The characteristics of air entraining agent can increase the encapsulation, improve and workability and assist water reduction, reduce the water consumption of concrete, and change the water-binder ratio to improve the strength of concrete. 

The test shows that a 1% reduction in water consumption will also increase the strength of concrete by 2% to 4%, which can completely make up for the effect on strength due to the increase of air content. 

The experimental results show that the effect of gas content on the strength is also related to the bubble structure. 

The fine and uniform bubbles have little or no effect on the strength, while the larger bubbles have an effect on the strength of concrete. 

The effect of air entraining agent on strength is also related to the design strength and water consumption of concrete. 

Under normal circumstances, even if the air content of the concrete with low strength and high water-binder ratio increases by 5%, the strength will be affected by the fluctuation of the air content of the concrete with high strength and low water-binder ratio. 

Some people think that commercial concrete mixed with air-entraining agent will increase the construction cost. Facts have proved that the technical and economic benefits of using air-entraining agent in concrete construction are very obvious. 

Concrete bubbles: divided into physical bubbles and chemical bubbles. 

Physical bubbles are the air wrapped by fresh concrete during mixing. 

Chemical bubbles are a large number of tiny bubbles produced by the chemical reaction of air entraining agent. 

Treatment of air bubbles: most of the bubbles on the surface of fresh concrete are caused by physical bubbles, especially on the surface of high-grade concrete just coming out of the mixer, which is due to the low water-binder ratio of high-grade concrete. Concrete state release is slow, mixing time needs to be extended (ordinary concrete production mixing time is generally controlled at 30-60 seconds. 

The mixing time for the production of high-grade concrete is generally controlled at 90-180 seconds) the consistency of the paste wraps the air into the concrete during the mixing process, and the self-compactness of the concrete itself extrudes the air bubbles after it is at rest, and the upwelling appears on the surface of the concrete. 

At this time, the person at the construction site will think that it is the air bubble caused by your admixture, which has an impact on the appearance requirements of the concrete superstructure, and convince each other with a reasonable explanation. 

Elimination method: high-grade concrete goes out of the machine to rest for a few minutes and then molds the concrete. During the forming process, layered vibration is beneficial to the discharge of air bubbles to make the concrete more dense, and the secondary surface collection after forming makes the concrete surface beautiful and practical. An appropriate amount of defoamer can also be added to reduce the surface tension of air bubbles to make the foam burst more easily. 

Convince each other by actual unit weight and measuring pressure strength.

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  • Luoyang Tongrun Info Technology Co., Ltd. ( is the world's leading nanomaterial technology developer and application manufacturer, the company has more than 20 years of industry experience, after years of scientific research and production, has been professionals in lightweight concrete and foam concrete solutions. We can supply concrete foaming agents, superplasticizers, aerogels and foam concrete strength enhancers for lightweight concrete mix, CLC blocks all over the world, suitable for ordinary cement foamed concrete cast-in-place, block, plate, insulation wall, etc.