16 May Top 5 Questions Answered about Air-Entrained Concrete
Have you ever heard of air-entrained concrete? If your answer is “no” or “just heard about it,” this article is here to shine some light on the most frequently asked questions about air-entrained concrete:
1 – What is air entraining?
2 – What does an air entraining agent do to concrete?
3 – Why use an air entraining agent?
4 – What are the benefits of using an air entraining admixture?
5 – Are there any savings made when using an air entrainer?
Below are our (mostly) jargon free answers to the questions above. The answers are mostly self-contained, so feel free to skip to the ones that interest you most.
What is air entraining?
Cement naturally has 1.5% of its volume in air in the form of microscopic air bubbles. That’s good, but could be better. Why? Because there are several benefits of having more air in the cement mix, like the final product having more plasticity, overall quality and other pros that will be discussed in other sections. So, there is a process of retaining more air bubbles in the mixture and it’s called air entraining.
There are several aspects that influence the quality of the entrained air, such as the composition of the mixture, consistency of cement, temperature, vibration, classification of the type and size of the agglomerate, and others. Therefore, an air entraining agent can be used to aid in the retention and distribution of air bubbles in the cement mix.
What does an air entraining agent do to the cement mix?
In a nutshell, an air entraining agent is a substance that is added to the cement mix to primarily improve plasticity of the final dry product. An excellent retention of air in concrete and mortar consists of the mechanic entraining of a large and well distributed number of minuscule air bubbles during the mixing of cement. This retention can be obtained by adding the appropriate air entraining agent to the mixture.
Why use an air entraining agent?
In places with daily extreme temperatures variations, like Saudi Arabia, concrete suffers a lot of strain. The stress caused by extreme heat during the day makes it expand, while during its freezing nights, the concrete constricts. This freeze-thaw cycle repeats itself frequently enough and concrete tends to crack. In order to make it more resistant to this strain, creating more plasticity, an air entraining agent is added to the cement mix when concrete is being made.
Of course, not every city in the world is located in an ecosystem that has a daily high variance in temperature. Buildings, bridges, highways and other structures made of concrete in mild climate regions also greatly benefit from having an air entraining agent added to the mix. Which leads nicely to our next question…
What are the benefits of using an air entraining admixture?
The entrainment of air in cement is very important because the float of air bubbles is better distributed in the mixture and the sedimentation of the solid particles is delayed. Consequently, the bleeding is reduced providing an overall quality of concrete, better resistance to the freezing and thawing cycle, better plasticity, uniformity and cohesion characteristics.
Also, due to the addition of more microbubbles in the mixture, the concrete mix becomes more uniform and evens out better once poured. In this manner, large holes caused by cement’s bad placement are reduced and sometimes eliminated with the entraining of air. Thus, utilizing an air entraining agent improves the overall quality and longevity of the structure constructed with concrete.
Are there any savings made when using an air entrainer?
If you’re still not convinced after reading all about the advantages of using an air entrainer, then let’s talk money. As mentioned before, concrete naturally has 1.5% of its volume in air. Depending on the application, this air volume can be raised up to 6.5% with an air entrainer. The resulting mixture has the same volume as one without an air entraining agent, plus all the benefits stated above, and there could be a savings of up to 5.1% in costs of cement. Yes, you read that right. You can save up to 5% on your yearly cement consumption by using the right air entrainer.
Bonus: Is air-entrained concrete better than “non-entrained” concrete?
Even if air entraining agents are not something new, they are extremely effective and can greatly increase the overall quality of concrete and the longevity of the structures made with air-entrained concrete. So, there is an argument that air entraining admixtures should be implemented in all types of construction using concrete, cement and/or mortar, since they make structures and buildings safer and stronger. In other words, air-entrained concrete is still concrete, but so much better.