CONCRETE CONTROL JOINTS
PREVENTING CRACKS IN CONCRETE

Above are the three types of control joints.

Concrete is used in construction for its hardness and very high compressive strength. Not being a flexible material it doesn't stretch or bend without cracking. Concrete does move though, it shrinks and expands. Buildings and other structures also move, contributing to cracking in slabs and floors.

If the concrete is tied to a structure or itself and tries to move, we get what's called restraint. This restraint causes tensile forces in the concrete and in most cases cracking will occur.

Concrete needs to be able to freely shrink as it dries or to expand and contract with temperature changes to help minimize any random cracking.

Properly placed control joints will allow concrete to shrink, expand, and contract, reducing the tendency for it to crack.

I've been in the concrete floor business for over 30 years. I've installed thousands of lineal feet of control joints in my concrete floors. I feel it's very important, if you want to minimize cracking, to take the time and plan in advance where and what materials you are going to use to install your control joints.

I still see concrete contractors skip this step and leave customers with cracks in their floors that are ugly and unnecessary.

In concrete slabs and floors there are three types of control joints:

1. Concrete expansion joints also referred to as concrete isolation joints.

2. Concrete contraction joints

3. Concrete Construction joints

Read about each one to learn how they are used to help control random cracking in concrete slabs and floors.

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