Saw cuts are used to create control joints that can be used to control the cracking in concrete that often happens because of shrinkage.
The right time to do the saw cuts should be when the concrete has enough strength but before the internal cracking starts.
They should be done with predetermined spacing as well.
There are many factors that determine when to make the cuts such as the mix design of the concrete, the type of aggregate used and also the type of admixtures.
When Is The Right Time To Add Saw Cuts To Concrete?
Determining when to add saw cuts to concrete depends on a lot of conditions as mentioned above.
For instance, the weather condition, the concrete mix and also the hardness of the concrete will come into play when deciding when to cut the concrete.
Of course, the type of equipment used to make the saw cuts also plays an important role.
If you cut the concrete too early, it will start ravelling. Here, the saw blade pulls the aggregate out of position making it messy and weak along the edge of the cut.
Also, cutting the concrete too early often causes uncontrolled cracking since it will start contracting when curing it.
If you are working in hot weather, you can start cutting around about 4 hours after the concrete is poured.
On the other hand, if you are working in cooler weather, you should wait for at least 12 hours before sawing.
If you’re not sure, you can actually make trial cuts to check whether the slab is ready and assess whether ravelling happens.
If you don’t notice any ravelling, the concrete is ready for cutting.
A lot of contractors often delay the sawing process to protect their equipment. That’s because their saw blades might suffer from excessive wear and tear.
Choosing the right saw to cut concrete depends on the type of concrete in the first place and how soon the cutting will start.
Some of the factors known to cause joint ravelling and excessive wear of the blade include:
- Cutting at a high speed
- Pushing the blade a too hard
- Using the wrong saw blade
- Using a saw with a ben spindle
Where Should You Saw Cut Concrete
You need to determine where the cuts will be done. The right area should be the centre of the column lines.
Space the joints between 24 and 36 times the thickness of the slab but this should be confirmed by a structural engineer.
If you are using concrete with a high shrinkage rate, reduce the cut spacing considerably. Other factors that determine where to cut include the following:
- Form square patterns
- Make continuous saw cuts
- Choose an area without continuous steel reinforcement from one slab to the next
- Create smaller cracks to avoid increasing cost trying to maintain the several joints
- If working in hot weather, create large squares before cutting the interior joints to allow fast setting of the concrete cracks in the larger areas.
How To Make Saw Cuts In Concrete
Analyse the slab thickness, the curing techniques, the base type and the length of the slab before cutting concrete.
Mark the joints with a chalk line and make sure the water runs all the way to the blade if you are using water cutting equipment.
The blade needs to reach the required depth for the best results. Here are a few recommendations to follow.
- Avoid twisting the blade
- The blade shouldn’t spin in the cut since it will increase the wear
- If the concrete has heavy rebar, you need blades with soft metal segment bonds for the best results.
Making saw cuts in concrete allows you to reduce the cracks that might be formed when it shrinks.
Knowing where, how and when to make the saw cuts is important for the control process.
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 www.megasaw.com.au/contact-us/