Controlled Crack In Concrete

Concrete cracks. It is unavoidable. However, cracking can actually be controlled and minimised. How? By cutting and putting a controlled crack before the concrete cracks on its own.

By cutting the concrete in strategic areas, you preempt random cracking and keep the integrity of the concrete – visually and internally. 

The cuts you make on concrete to actually prevent cracks are called “control joints.” The depth and length of the control joints will vary depending on the type of concrete and its usage.

Making the cuts needs to be precise and timely. Otherwise, you will cause more harm than good.

When To Cut Concrete?

Timing is important when it comes to cutting control joints into the concrete. If you do it too soon can it cause ravelling which causes the aggregates to be pulled out of position, weakening the edges of the concrete that was cut.

On the other hand, cutting too late can cause even more cracking. When it comes to cutting concrete, you have to consider the following factors:

  • The concrete mix
  • Aggregates used
  • The hardness of the concrete
  • The type of equipment used
  • Weather conditions – if the weather is hot, you can start cutting as early as four hours after you pour the concrete. If the weather is cool, cutting needs to start 12 hours after the concrete was poured.

Cutting Tip:

The best way to determine if the concrete is ready for cutting is to make test cuts to check for ravelling. When the ravelling stops, you should start cutting.

Where to Cut Concrete to Prevent Cracking?

Cutting control joints should be strategic, otherwise, cutting is useless. Always consult a structural engineer before making the cuts.

Usually, control joints should be spaced at 24 to 36 times the thickness of the concrete. They should be spaced between 4 to 6 metres depending on the amount of reinforcement the concrete has.

You also have to consider the shrinkage of the concrete. This is why you need to consult your structural engineer when making the cuts.

Concrete Cutting Tips

Once you have determined the right time to cut control joints into your concrete, complete the following steps:

  • Mark the areas you are going to cut. Use bright chalk powders to mark the areas. If you are wet-cutting, use a bright-coloured crayon to mark the spot.
  • Use the right saw for the type of concrete you are cutting. There are various types of concrete saws you can use in cutting concrete. For example, large floors will require the use of a walk-behind saw. For smaller concrete, hand-held concrete saws can come in handy. 
  • Choose the right saw blade. Diamond blades are more popular and highly recommended. They make more precise, clean cuts and produce less concrete dust.
  • Control the dust. Make sure you have dust collectors and other necessary tools in controlling dust. Concrete dust contains crystalline silica which is very harmful to your health. Crystalline silica can cause lung scarring and can cause Silicosis, a fatal, incurable, irreversible disease. Use the wet cutting method when making control joints. Wet cutting produces less dust and keeps the concrete dust from becoming airborne and getting inhaled.
  • Use waterproofed, GFCI extension cord when using electric saws. GFCi or Ground Fault Circuit Interrupter is an affordable device that is built into your power cord to protect you from power surges, overloads, and electric shocks. 
  • Use a guide board. Secure a straight smooth board outside the chalk line to use as your guide in making straight, clean lines. 
  • Do not force the blade. Do not push too hard. Just let the saw do the work. All you need to do is guide it in the direction you want to cut. Pushing the saw too hard can cause overheating and can damage the saw.
  • Try to form square patterns.
  • Make shallow continuous cuts.
  • Do not twist the saw blade. You will damage the blade, jeopardise the finish of concrete, and put yourself in harm’s way.
  • Use saw blades with soft metal segments when cutting concrete with heavy rebar.
  • ALWAYS use the required PPE or Personal Protection Equipment. The Australian Code of Practice for Concrete and Masonry Cutting and Drilling requires the use of the following:

Safety helmet

Safety footwear – steel-toed shoes are recommended

Safety goggles

A face shield

Hearing protection

Sun and weather protection

Gloves to improve hand grip  and reduce force and vibration

Respiratory protection when hazardous dust or fumes  cannot be eliminated

  • Avoid using loose-fitting clothing or jewellery. Long hair and long beards can be risky too.

Cutting concrete yourself is doable but we do not recommend it. Aside from the health risks, your lack of training might just cause more damage to your concrete and cost you thousands of dollars in repairs. Let the professionals handle the work for you. 

If you are looking for a specialist concrete cutting company who uses only the best practices to get the job done right, then please call us at Megasaw on 1300 920 419 or contact us through our website