Best Approaches To Adopt For Reducing Shrinkage And Thermal Cracking In Concrete

When depositing concrete in a form, gravity causes all the heavier particles like aggregate or cement to separate and sink. It also displaces the water. The water has almost nowhere to do; it ultimately ends on the surface. It is referred to as bleeding water and will generally evaporate. The evaporation of any bleed water will form a negative pressure specifically within the paste.

All of the water getting evaporated will be replaced by any extra water within the mixture. So, whenever the rate of rising water fails to match with the rate of evaporation, there are high chances of your ready mixed concrete mixture drying out and shrinking.

So, now, it becomes crucial to know about the most critical contributors that help in instant surface moisture evaporation. Let’s talk about these factors in the below-mentioned section:

• Low Water To Cement Ratio

If your cement to water ratio is very low, it suggests that your structure does not have an adequate amount of water to replace what has been evaporated already.

• Low Humidity

Everyone had experienced this type of situation in their lives when they got chapped lips and knuckles in the winter season. It occurs mainly due to the low humidity when the dry air takes away the moisture from your skin. A similar thing happens to your concrete structure as well.

• High Cementitious Content

The more cement you contribute to your mixture, the more paste you will get. In this case, it would be a good idea to keep in mind that the paste in concrete is often much prone to shrinkage.

• High Temperature

The hydration of your cement structure will produce an excessive amount of heat. If you fail to control that heat, it will cook the water off. You can compare this to a situation where you have left a pan of water to sit on the stove for a prolonged period.

• Wind

Air currents blowing over your concrete structure will take away all the moisture. It is one of the significant reasons you should take utmost precautions and care when casting a concrete structure outside.

Consequences Of Cracking And Shrinkage

The concrete surface looks unsightly if cracking and shrinkage occur in it. As soon as the cement reacts to the water, cracks form. These cracks can range from a few inches to several feet based on the structure.

When the wind blows over the concrete surface, you will notice the formation of cracks that will again follow a pattern running perpendicular to the wind flow. Similarly, the cracks will follow a random pattern if the wind is swirling.

Also, cracks tend to form on the horizontal areas of the structure where the water is still evaporating. One of the crucial things to note is that cracking caused by shrinkage does not threaten the entire structure, but it can lower the product’s lifespan.

The concrete surface plays a significant role in preserving the rebar against any hazardous substance. Any expanding oxidising steel can result in extra cracks, leading to more exposed steel and corrosion. If any crack is present on the surface, it provides an opening for dirt and corrosive materials to enter the structure.

It might further increase the chances of corrosion of your reinforced concrete present beneath. So, it is essential to take adequate precautions beforehand to avoid such issues successfully. If you fail to be careful, it will eventually reduce lifespan.

What To Do To Avoid Such Issues?

Below are given some of the measures that you can take to avoid any possibilities of cracking and shrinkage:

• Consider Adding Fibres

You can add some amount of fibres to your mix. By doing so, you would enhance your structure’s tensile strength effectively. It is considered a great approach to prevent tensile stress from exceeding the overall power of your mix. From this, you need to have a proper understanding of all traits of the fibre and how to batch them appropriately into the concrete, as it will affect the water demand of the mix.

• Windbreaks And Sunshades

If you are looking forward to reducing the total wind velocity, one of the best approaches would be to place windbreaks and sunshades around the concrete structure. Many professionals use damp burlap, which helps protect the concrete structures from the sun’s extreme heat. It also helps to attain an ideal moist curing condition.

• Fog Sprays

Another thing that you can do is to use a fog spray. It works by effectively increasing the relative humidity of the air that surrounds the concrete structure. In this aspect, an important thing to note is that high humidity levels tend to correspond with a lower evaporation rate.

So, your concrete supplier will suggest that you keep your concrete in a humid environment. You would be able to get a high-strength and reliable concrete structure by allowing it to cure as soon as possible while also maintaining consistency.

One of the most common mistakes people often make is not paying attention to bleed water which has worked its way back into the first concrete layer. It works to increase the top concrete layer’s total water to cement ratio.

It leads to a great reduction in overall strength and other significant problems. It also creates an issue by getting rid of water that would ideally evaporate, increasing the structure’s temperature and making it more prone to cracking. However, if you observe that cracks have occurred, you can protect them against further damage by using sealants and fillers.

Wrapping Up

We hope now you have a good idea about the best ways to reduce shrinkage and thermal cracking in concrete. Have any further queries about ready mix concrete? If so, feel free to contact RMS Concrete today, a leading ready mix concrete Essex supplier.