When concrete is poured, it is very important to cut expansion joints in the concrete. By cutting control joints in the concrete you can better control the random cracking that inevitably occurs in concrete slabs soon after the concrete is poured and set.
Concrete saw cutting can be a hard task, but cutting expansion joints can be harder still. This is because there is, even more, to know, such as when to time your cutting, where to place the cuts, and what techniques work best.
This guide will help to ensure that you are making the highest quality cuts to ensure the best possible finish for your concrete.
What Is expansion joint Cutting?
After the concrete is poured and it begins to set it actually shrinks as it hardens, condensing into one solid mass. As the moisture leaves the concrete and it hardens, the concrete becomes prone to random cracking known as shrinkage cracks. Any number of things can affect shrinkage cracks such as hot weather, elasticity, tensile strength, and more.
Control cuts help to alleviate random cracking by creating weak points in concrete slabs, forcing cracks to form along the cuts rather than appearing in more obvious, unsightly places in the concrete slabs.
When to Saw Cut Concrete
It’s very important to understand when the best time to start saw cutting concrete slab is. Cutting too early can cause ravelling, leaving a messy edge along any cut made. If you cut too late, you can actually create more random cracking than would have occurred had you not begun cutting expansion joints at all.
So when do you want to begin saw cutting concrete slab?
After the concrete is poured, you can start cutting your concrete slabs within six to eighteen hours. During particularly hot weather, you can even begin as early as four hours after the concrete is poured.
Before you get to work with your concrete cutting saw, however, it’s a smart idea to make small trial cuts to check for ravelling. If you don’t see the telltale messy edge of ravelling along the edge of your cuts, you are good to begin cutting control joints.
Where to Saw Cut Concrete
Before you begin saw cutting concrete slab, you must first select where these cuts will be done on the concrete. It’s recommended that you start cutting control joints on or at the centre of column lines.
Joints should be spaced at 24 to 35 times the slab thickness, however, the exact spacing should be decided by an engineer familiar with the individual project. This spacing equates to approximately 3 to 5.5 metres depending on the amount of reinforcement that the concrete slab has.
If the concrete slabs being used are of a high shrinkage, it is recommended that the spacing between cuts is decreased.
When choosing what area to begin cutting expansion joints, select an area that does not have any steel reinforcement continuing from one slab to another.
How to Saw Cut Concrete
Once you’ve chosen where to place your cuts, mark them with a chalk line so you have a guide to help keep your cuts accurate. There are many options of tools and methods available when saw cutting concrete slab.
What Are The Right Tools?
The recommended tool to use by concrete saw cutting companies is a specialised concrete cutting blade circular saw. These are handheld saws that are built for heavy-duty work and it’s recommended that you use a diamond concrete cutting blade with the saw.
As mentioned before, diamond blades are the best choice of concrete saw blades available. This is because diamond blades are specifically designed to slice through the most rigid and dense surfaces possible.
Diamond concrete cutting saw blades are available for both wet and dry cutting. When choosing a blade for your concrete cutting saw, diamond blades are an easy choice.
What Methods Are There?
There are two main methods when cutting concrete with a circular saw:
It is a very popular concrete cutting method that uses water to wet the surface of the concrete slab. Wet cutting helps to control silica dust that is created when saw cutting concrete slab. Silica dust poses a severe health risk as it harms your lungs and respiratory system, and can even cause lung cancer. By wet cutting concrete, you reduce dust concentration by at least 85%.
Wet cutting also helps to prevent diamond blades from overheating when saw cutting concrete slab.
It is another method sometimes used, and this is where the concrete is kept dry when saw cutting concrete slab. Alternating and thin cutting is strongly recommended to let air flow around the handheld concrete saw blades to reduce overheating.
When concrete saw cutting, aim to cut to a depth of one quarter to even one-third of the concrete slab thickness. When cutting concrete with a circular saw you don’t want to cut too shallow or else risk random cracking. If you are cutting control joints too deeply then aggregate interlocking will not be sufficient to transfer loads.
Tips for Concrete Saw Cutting
Use these tips to make sure you’re cutting concrete with a circular saw to the best level of quality possible:
- If wet cutting, ensure water is running all the way to the blade
- Don’t twist the concrete cutting saw blade
- Don’t let the concrete cutting saw blade spin in the cut, or you’ll increase wear
- Always keep safe and wear appropriate safety gear
- When cutting expansion joints, retract the blade and let it run every 30 seconds to reduce the chance of overheating
- Never force concrete saw blades into a cut, or exert too much pressure. Let the weight of the concrete cutting saw do the work.
Concrete saw cutting can be a difficult task, and making a mistake can increase the concrete saw cutting cost. If you aren’t feeling confident using a concrete cutting saw in a DIY project, it’s wise to let professional concrete saw cutting companies do the work for you.
The experts at Diamond Cut have years of experience working on many projects from civil, to industrial and commercial. Get in touch today to see how Diamond Cut can help you with saw cutting concrete slab.