How to prevent concrete cracking

The majority of concrete cracking is preventable - but there are many different reasons that it can happen. There’s enough to worry about on the building site, and being at fault for cracks can mean significant financial costs and brutal conversations on the worksite.

At Found, we’re obsessed with making your concrete experience easy. In this article we’ll go through the most common reasons for concrete cracks, the easy steps to prevent concrete cracking and what to do if the concrete has cracked. 

This is a good article for sharing with both your teammates or your customers who may have questions about concrete.

Why does concrete crack?

Cracking occurs when the concrete begins to dry. As concrete hardens, it loses water and begins to shrink. 

If the concrete does not have anything to control this shrinking and help it flex, cracks or hairline fractures start to occur. 

Concrete cracking happens but there are ways to prevent it from occurring, which we’ll detail below.

How to prevent concrete cracking when on site 

Cure your concrete.

What is curing your concrete?

Curing your concrete means to condition your concrete. As concrete loses moisture and begins to shrink it is seeking moisture. Curing is a method of giving the concrete that moisture to prevent it from cracking and fracturing

What’s a cost efficient way to cure concrete?

The cheapest way to cure concrete is water curing, which is where you hose the concrete after placed with water. You’ll need to make sure you pond the concrete, by using sand barriers or bag barriers around the area of the concrete which keeps the water sitting on top of the concrete and not running off and drying it out. After this, putting plastic sheeting on top of the cured concrete means that you’ll protect it from natural elements like the wind or kids who want to write their name in it.

Simple but effective - water curing.

How to increase the time you have to work your concrete

Use a concrete retarder.

What is a concrete retarder?

Concrete retarder is a chemical solution that slows the drying of concrete. It means that you have more time to work with the concrete and avoid air gaps being created in concrete which are known as voids. 

When should I use a concrete retarder? 

It may be best to use a concrete retarder on any project if you need more time to set your concrete.

It’s especially useful when it's a hot day, or it's windy, or if the truck is a fair distance away from the site.The retarder will slow the concrete reaction down, giving you more time to play with it.

Can you do anything once the concrete has hardened? 

Yes. For hairline or small cracks, concrete caulk or liquid filler can be used to seal the cracks. For all cracks you will need to chip it out making an upside down V and ensure it is clean and dry before using the seal, or it will not bind properly.

For large cracks, a concrete patching compound can be used to fix and seal the crack.

For very large cracks or where the concrete has been completely compromised, you may need to pull the concrete up and repour. 

How many days does it take for concrete cracks to occur?

The majority of cracks occur 2-3 days after concrete has been poured. 

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