Permeability Of Concrete

Oct 22, 2021 | Structural services | 0 comments

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We all know that concrete is an incredibly strong and durable material. It is especially durable if it is kept under the right conditions. One of the conditions that deteriorates concrete is moisture. When moisture enters concrete, it begins to break down the concrete and it can completely damage structures. However, even though concrete breaks down with water, we still have structures that are submerged in water. This is possible due to the low permeability of concrete. 

What is Permeability?

Permeability is defined as the property that controls the flow of fluids into a solid that has pores. Permeability in concrete refers to the amount of water, air, or any other substance that can enter concrete pores once its dry. The permeability of concrete depends heavily on the size of the pores, how close the pores are to each other, and how clear the path is for substances to penetrate. Pores that have a diameter of 120nm-160nm are the major reason for causing permeability in concrete. 

If concrete is highly permeable, then that is a major reason for concrete deterioration. In construction, it is preferable for concrete to be as impermeable as possible in order to make sure that the concrete is durable. Concrete that is easily permeable won’t stand high rain seasons, freeze-thaw cycles of an area, or areas with high flood risks. Anything built with highly permeable concrete will not stand that test of time. 

Factors Which Influence Permeability of Concrete

There are a couple of factors that influence the rate of permeability of concrete. Some of those factors are the water to cement ratio, concrete compaction, concrete curing, and the age of concrete. These are the factors that are kept in mind when mixing the concrete that will be used in the creation of a structure.  

Water to cement ratio has a heavy influence on the rate of permeability of concrete. The higher the water to cement ratio, the greater the permeability of the concrete. Therefore, it is ideal that concrete being used have a low water to cement ratio so that we can have an impermeable concrete that will be sure to last. When the cement gets mixed with the right amount of water, it makes more paste, and the paste can fill any pores more easily. 

Concrete that is compacted effectively, any air bubbles or trapped water will be removed. When these things are removed, it decreases the number of connected pores that exist in the concrete which in turn makes the concrete less permeable. 

Allowing for enough curing of concrete allows for proper cement hydration. The water sprayed during the process of curing allows the concrete to gain strength and it reduces the number of pores it may have. The smaller the size of the pores, and the less pores that there are, the less permeable the concrete will be. 

Other factors that have an impact on the permeability of concrete even though small are the age of concrete, the properties of the cement being used, the aggregates in the mix, among others. 

Why Is It Important For Concrete To Be Impermeable?

It’s important for concrete to be as impermeable as possible because moisture breaks down concrete. It is one of the biggest reasons for foundation issues in structures. Concrete is strong, but not unbreakable and the freeze-thaw cycle that results when trapped water gets mixed with changing weather patters would crack the concrete. 

In reinforced concrete if there is water and air trapped inside, it will cause the steel to erode. The erosion leads to the expansion and cracking of the steel.

The durability of concrete is basically dependent on how permeable it is. If water or any other damaging substances get inside of the concrete, it will be broken down. That’s why ensuring that the concrete we use is as impermeable as possible is the first line of defense against environmental factors that can be detrimental to the foundation of structures. 

Can Permeability Be Tested?

A standard test method known as the rapid-chloride permeability test is one of the most accepted tests to determine how permeable the concrete being used is.

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