The saw cut must be deep enough to ensure any reinforcing passing through the joint is cut through when the slab is cut.
Saw cuts in concrete slabs nz.
Following is a rundown of common concrete cutting tasks from dinky to monster sized and the best tools and techniques for handling them.
The prospect of cutting concrete can be daunting but it doesn t have to be.
If of your slab s thickness doesn t reach 1 make sure you still cut at least a 1 depth.
When to saw cut concrete.
In summer this should be done no later than 24 hours after pouring.
For slabs designed to nzs 3604 2011 the spacing of saw cut joints shrinkage movement joints and location of the reinforcing mesh are all important in avoiding shrinkage cracking.
The reinforcing mesh needs to be at 30mm cover to the top of the slab see figure 2.
When you are looking for saws to do relief cuts make sure that it is a down cut.
A good rule of thumb is to make your cut the thickness of your concrete.
They may be formed either by saw cutting the slab after it has hardened or by casting a crack inducer into the slab when the concrete is poured.
Most of the battle can be won by simply selecting the right tools.
In winter it should be done within 48 hours.
One thing to be aware of before we go further.
Cut joints deep enough cut joints 25 of the depth of the slab.
A 4 thick slab should have joints 1 deep.
Slab for one quarter of the slab s depth see figure 2 and must not damage the dpm underneath.
Use a low rpm setting when cutting through the concrete to keep the blade from overheating and throwing chunks of concrete from the surface of the slab.
Saw cutting cuts joints as soon as the concrete is hard enough that the edges abutting the cut don t chip from the saw blade.
Its main function is to prevent shrinkage cracks occurring between saw cut joints.
Cutting too early causes raveling an effect created by the saw blade pulling the aggregate out of position leaving a messy weakened edge along the cut.
This method allows the placing of concrete for a complete floor area in one operation.
In addition to the concrete mix and the weather conditions determining when to saw concrete is based on the concrete s hardness as well as the type of cutting equipment used to make the saw cuts.
To cut concrete too thick for the saw.
Control joints that are cut into the slab should be formed within 24 48 hours after pouring depending on.
Try a concrete saw.
In order to ensure that shrinkage cracking occurs at a contraction joint a plane of weakness must be created by forming using crack inducing tapes or formers or cutting a groove to a depth of at least one quarter of the slab thickness.
Place joints under walls or under carpet areas.
However if the cut can be formed early enough by a suitable grooving tool or early age saw cutting some.
How to cut joints groover tools cut joints in fresh concrete.
