What are concrete joints, and why do you need them?

Save your concrete from cracks!

Let’s talk about cracks in sidewalks and other concrete surfaces. Some resemble delicate spiderwebs, while others look like mini-Grand Canyons. While they may be artsy, it’s best to avoid them as much as possible, as structural types of cracks can weaken the integrity of a build.

What causes cracks in concrete?

While cracks can appear when concrete is first set, they can also occur much later. Changes in temperature during spells of hot and cold weather, as well as extreme moisture, make concrete expand, contract, and crack.

Luckily, there’s a way to save your next concrete project from these dreaded fissures. Concrete joints to the rescue!

What are concrete joints?

Think of them as pre-planned cracks. These joints are inserted before the concrete is poured to prevent it from cracking as it dries. Concrete joints are like a form of stress relief for concrete slabs, giving them the space they need to expand and contract as they go through the curing process or experience temperature changes in the years to come. They’re made of metal, asphalt, fiber, foam, cork, and more.

How do you know if you need concrete joints?

The simple answer is: whenever concrete touches another structure or slab. For example, this could be where a pool deck meets a pool house, or where one concrete slab meets another slab, and so on. Some sections of concrete may contract or expand more than others, creating pressure, which leads to cracks. Concrete joints allow each slab or structure to move independently of one another,  keeping the pressure to a minimum and the slab in one piece.

What are the different kinds of concrete joints?

In the world of concrete joints, there are three important types to know:

1. Construction joints
You’ll see these joints placed in sidewalks and slabs to prevent a long stretch of concrete from cracking. They’re used when one concrete slab meets another and can even be placed at the end of a pour.

2. Expansion/isolation joints
The “isolation” part of their name is because they isolate the concrete slab from the structure the concrete touches. The “expansion” part means these joints allow horizontal and vertical movement of each slab.

3. Contraction joints
These joints are groovy! They literally have sawed, formed, or tooled grooves which help regulate the expansion of cracks.

Use the best concrete joints for your project

Got a DIY concrete project on the horizon? If you need concrete and expert advice, Mathews Readymix can help. We’re happy to share advice on the right concrete joints, admixtures, and other products for your job. Contact us today to find out more!