Some vital points to make saw cuts in concrete
The purpose of saw cuts is to make control joints in concrete to facilitate managing cracks which may occur because of shrinkage. The cuts should be created at a predetermined spacing and only as soon as the concrete has attained adequate strength but prior to internal cracking starts. So, the timing of saw cuts should be maintained properly. The exact time for creating cuts is based on several factors along with the type of admixtures and aggregate used in the concrete, the air temperature, and the concrete's mix design.
When to Saw-Cut Concrete: Besides, the concrete mix and the weather conditions, it depends on rigidity of the concrete and the type of cutting equipment applied to make the saw cuts. If the cutting is done ahead of time, an effect produced by the saw blade dragging the aggregate out of position, departing a rough, weakened edge along the cut. It also produces undo wear on diamond concrete saw blades. Sawing slowly can lead to uncontrolled cracking since the concrete contracts throughout curing.
In hot weather conditions, saw cutting commences after four hours once the concrete is poured. In cooler weather, sawing should not commence for 12 hours after pouring. The most effective method to find out whether the slab is prepared is to create trial cuts to examine raveling. Saw cutting should be commenced when the raveling stops throughout these trial cuts.
Some contractors defer sawing to defend their equipment and saw blade to minimize blade abrasion. Different types of saw blades are utilized on the basis of the concrete type and how quickly the cuts can be started. The following other factors can produce extreme blade wear and joint raveling:
• Pushing the blade too hard
• Saw cutting is done at high speed
• Applying a saw with a ben spindle
• Application of an improper saw blade
Where to Saw-Cut Concrete: Prior to commence saw cutting concrete, it is crucial to choose where these cuts will be created. It is will be useful to start saw cuts on or at the center of column lines. Joints shall be placed at 24 to 36 times the slab thickness but it should be approved by a structural engineer. Joint spacing generally varies among 10 to 18 feet based on the amount of reinforcement in the slab.
How to Saw-Cut Concrete: Various factors like curing methods, slab thickness, slab length, and base type should be analyzed prior to determine where joints should be cut. As soon as the joints are placed to be cut, mark them with a chalk line.
If water cutting equipment is applied, ensure that the water is running all the way down to the blade. The blade should be allowed to attain the desired depth, then start walking or moving the equipment following the chalk like mark. Here are some recommendations when sawing concrete:
• Never twist the saw blade.
• Do not allow the blade spin in the cut, since it will raise wear on the bond.
• While cutting concrete with heavy rebar, apply blades with soft metal segment bonds.
• It is recommended to utilize use the required PPE (personal protection equipment).
Depth of creating Saw Cuts: A proper rule of thumb is to cut the joints one-quarter to one-third the slab thickness. For a 6-inch-thick slab, it signifies cutting 1.5 to 2 inches deep. Make sure that the saw cut depth is according to the structural engineering specifications. If the joint is adequately deep, aggregate interlocking will not be sufficient to transmit the loads. If the saw cut is too shallow, random cracking may happen.