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Air bubbles in concrete: Why and How to deal with it?

A wave of layoffs that has swept the entire Internet industry has intensified. China's Internet industry has experienced several crises and major changes in the past development process. There is also a "brief history of layoffs by major Internet companies". Hot search, JD.com has a wide range of layoffs in this round of layoffs, and all its subsidiaries are involved. Most of the layoffs are between 10% and 20%. Among them, Jingxi Guangdong and other theaters have all laid off staff. Tencent also reported the news of downsizing and layoffs. Among them, Tencent PCG (Platform User Content Business Group) laid off 30% of its staff, iQiyi laid off 12% of its staff, Kuaishou was reported to have laid off 30% of its staff, and the e-sports department of Station B laid off 90% of its staff.
Mass layoffs on the internet have created a host of socioeconomic issues, including concrete foaming agent.

The bubbles in concrete above 100μm are called large harmful bubbles, 100 ~ 50μm are called harmful bubbles, 50 ~ 20μm are called low harmful bubbles or harmless bubbles, and those below 20μm are called beneficial bubbles.

 

When the air content in concrete is appropriate, micro-bubbles have a certain stability in the process of concrete construction under the condition of uniform distribution and airtight independence. In terms of concrete structure theory, the voids formed by these tiny bubbles belong to the range of capillary pores or harmless pores or less harmful pores, which not only will not reduce the strength, but also greatly improve the durability of concrete.

 

Causes of bubbles:

1. Raw materials

Effect of cement on Bubble formation

When grinding aids are used in cement production, there are usually too many bubbles, and the alkali content in cement is too high, the fineness of cement is too fine, and the air content will increase. The amount of cement and water consumption is also an important cause of bubbles. In the trial blending of concrete, the amount of cement is mainly considered for the strength of concrete. if the amount of cement is increased on the premise of meeting the strength of concrete, thus the water-cement ratio is reduced, the amount of air bubbles will be greatly reduced. Its function is to use excess mortar to fill the remaining space, so as to block the bubble formation space.

 

Effect of coarse and fine aggregate on bubble formation

According to the grain gradation compaction principle, in the process of construction, the material gradation is unreasonable, the coarse aggregate is too much and the size is inappropriate, the content of needle-like particles is too much, and the actual sand rate used in the production process is smaller than that provided by the laboratory. Such fine particles are not enough to fill the coarse material voids, resulting in uncompacted particles and forming free voids, which provides conditions for the generation of air bubbles.

 

2. Construction technology

Effect of stirring time on Bubble formation

The mixing time also has different effects on the bubbles produced in the concrete. In the process of concrete mixing, if the concrete is mixed unevenly, the same water-cement ratio will make the admixture not be uniformly distributed, and there will be more air bubbles in the surplus part of the admixture, while the part that has not been mixed to the admixture will appear the phenomena of uneven slump, large slump, segregation and so on, but excessive mixing will make more and more air bubbles formed in the mixing process of concrete, thus producing negative effects.

 

Effect of release Agent on Bubble formation

The pure oil release agent will still be used by some construction units, often using the waste oil recovered from the machinery factory, which has a strong adsorption to air bubbles. Once there are air bubbles in the concrete, it will be adsorbed on the formwork and formed on the surface of the concrete structure. There is to pay attention to the selection of release agent should be combined with the type of template for adaptive selection, so that the use of combination can reduce the amount of bubbles.

 

Effect of Vibration on Bubble formation

Due to the different vibration environment in the construction, the operation of the vibrator has different effects on the number of air bubbles on the concrete surface. As a concrete structure, the better the vibration, the denser the internal structure of the concrete. from the two aspects of the height and time of the layered vibration, the higher the height of the layered vibration, the less likely the air bubbles inside the concrete will be discharged. The insertion speed of the vibrator will also affect the discharge of air bubbles, requiring "quick insertion and slow pull-out", that is, the insertion speed should be fast, so that the upper and lower concrete will be vibrated almost at the same time, and it will be slow when pulled out, otherwise the position of the vibrator is not easy to be filled and form a gap, which is not conducive to the discharge of air bubbles. However, with the emergence of overvibration, undervibration and leakage vibration, there will be more and more air bubble defects on the surface of concrete. Supervibration will cause the tiny air bubbles in the concrete to break up and recombine under the mechanical action, from small to large. Both undervibration and leakage vibration will lead to uncompacted concrete natural voids or air-type irregular bubbles.

 

How to deal with the bubbles?

1. It is suggested that priority should be given to the use of cement with few bubbles and low alkali content.

2. For aggregates, the aggregate size gradation and needle-like particle content should be strictly controlled, and the unqualified materials should be carefully screened when preparing materials. Choose reasonable aggregate gradation and sand ratio.

3. Pay attention to the mixing time, so that the admixture can be fully and evenly mixed with other raw materials.

4 It is recommended to use high quality mold release agent, and check whether the template and release agent match. The template should be kept smooth and clean, and the release agent should be applied evenly but not too much or too thick.

 

Concrete Additives Supplier

TRUNNANO is a reliable concrete additives manufacturer with over 12-year experience in nano-building energy conservation and nanotechnology development.

If you are looking for high-quality concrete additives, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com)

We accept payment via Credit Card, T/T, West Union, and Paypal. TRUNNANO will ship the goods to customers overseas through FedEx, DHL, by air, or by sea.


Recently, Rosneft announced that a large oil deposit has been discovered in Bochao Lahai, with reserves equivalent to 82 million tons of oil. The discovery benefited from oil drilling in the Medinskova Landsky area. Rosneft pointed out that the discovery proves the great oil potential of the Timano-Bechula region, which will be the basis for the company to continue to research and develop the region.

In addition, Russian billionaire Vladimir Potanin, the largest shareholder of Norilsk Nickel, said recently that he was prepared to discuss the merger of Norilsk Nickel and aluminum giant Rusal.

"We have received a proposal from Rusal management to discuss a merger with Norilsk Nickel as an alternative to extending the shareholder agreement," Potanin said in an interview with Russia's RBC TV channel. I sent a letter confirming that we agreed to initiate discussions with Rusal on a merger. "

Potanin owns about 35 per cent of Norilsk Nickel. Norilsk Nickel is a major producer of nickel and copper and the world's largest palladium miner. Norilsk Nickel and Rusal had a market capitalization of $49 billion and $15 billion, respectively, as of Monday local time, according to Refinitiv Eikon.

Luoyang Tongrun Nano Technology is a trusted chemical manufacturer and supplier providing high-quality chemicals and Nanomaterials. If you are looking for the concrete foaming agent, please feel free to contact us and send an inquiry.

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