What does a saw cut mean?
Sawcutting involves the formation of joints or breaks in a PCC mass (slab) by the use of mechanical cutting tools.
When should I use saw cuts in concrete?
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.
What are the saw cuts in concrete called?
These cuts are called Construction Cuts (also called Construction joints, Expansion Cuts, or Expansion joints) and must be correctly positioned and done within 24 hours of the concrete being poured, otherwise there is a significant risk of concrete cracking (unless other jointing methods are used).
How do you cut joints in concrete?
MORE JOINTING TIPS Cut joints 25% of the depth of the slab. A 4" thick slab should have joints 1" deep. Groover tools cut joints in fresh concrete. 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.
When Should saw cuts be done?
Joints should be sawed as soon as the concrete can withstand the energy of sawing without raveling or dislodging aggregate particles. For most concrete work, cutting should take place within the first 6 to 18 hours and never beyond 24 hours.
How often should you put expansion joints in concrete?
Usually, expansion joints should be no farther apart than 2 to 3 times (in feet) the total width of the concrete (in inches). So for a 4 inch thick concrete slab, expansion joints should be no more than 8 to 12 feet apart.
Do I need control joints in concrete slab?
Concrete expands and contracts with changes in temperature and moisture. If not properly controlled, cracks can begin to appear. Placement of concrete control joints and expansion joints are crucial when designing and pouring concrete slabs and sidewalks.
Do you need expansion joints in concrete?
Concrete expansion joints are particularly important where there have been consecutive concrete pours and are also useful when laying concrete within an area bordered by walls or buildings or if objects such as manhole covers need to be incorporated.
Do you need expansion joints in concrete sidewalk?
A.: According to several industry sources, expansion joints, even at 50-foot intervals, are not necessary for the sidewalk project. Long stretches of concrete do not require intermediate expansion joints.
How deep should you cut joints in concrete?
A good rule of thumb is to cut the joints one-quarter to one-third the slab thickness. For a 6-inch-thick slab, that means cutting 1 1/2 to 2 inches deep. Ensure that the saw cut depth meets the structural engineering specifications.
Can you cut control joints in old concrete?
The best time to start cutting control joints into concrete is after the poured concrete has dried enough for you to saw through without dislodging or ravelling the particles of the poured mixture. In most cases, control joints should be cut into concrete after it has had 6 to 18 hours of drying time.
How many saw cut concrete?
Cuts should be approx. 2-3 times the thickness of your slab in feet. For example, a 6” slab would have cuts 12' – 18' apart. This is strictly a guideline to work from.
Why do they cut lines in concrete?
These lines are called contraction lines and this is going to help in relieving the stress that is going to cause the cracks that are going to be present in the concrete.
How deep should saw cuts be in concrete?
As far as the depth of the cut is concerned, professionals recommend cuts ranging from one quarter to one third of the thickness of the slab. Simply put, this means that the cutting depth should be restricted to around 2.5 inches for an 8 inch thick concrete slab.
Are concrete expansion joints necessary?
Expansion joint failure can happen for several reasons, but regardless concrete needs a buffer as it goes through the natural cycles of expansion and contraction. So, this has always been the case, and this is why expansion joints are necessary.
Why do we use saw cuts in concrete?
Saw cuts are a used to create control joints in concrete, which help control where cracking occurs due to shrinkage. The cuts should be made at a predetermined spacing and only after the concrete has obtained sufficient strength but before internal cracking begins. Therefore, the timing of saw cuts is critical.
How to cut joints with water?
Once you've laid out the joints to be cut, mark them using a chalk line. If you're using water cutting equipment, make sure that the water is running all the way down to the blade. Allow the blade to reach the required depth, then start walking or moving the equipment following the chalk like mark.
How far apart should joints be on a concrete slab?
Joints shall be spaced at 24 to 36 times the slab thickness but this need to be confirmed by a structural engineer. Joint spacing normally ranges between 10 to 18 feet depending on the amount of reinforcement the slab has. 1 If you are using high shrinkage concrete, you might want to decrease the cut spacing.
Why delay sawing concrete?
Some contractors delay sawing to protect their equipment and saw blade to reduce blade abrasion. There are several types of saw blades that can be used, depending on the concrete type and how soon the cuts can be started. Other factors that can lead to excessive blade wear and joint raveling include:
How long after concrete is poured can you cut?
In hot weather conditions, saw cutting may start as soon as four hours after the concrete is poured. In cooler weather, sawing may not start for 12 hours after pouring. 1 The best way to determine whether the slab is ready is to make trial cuts to check for raveling. Saw cutting should start as soon as the raveling stops during these trial cuts.
What happens if you cut concrete too early?
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 also causes undo wear on diamond concrete saw blades. Sawing too late can result in uncontrolled cracking as the concrete contracts during curing.
Can you twist a saw blade to cut concrete?
Here are some recommendations when sawing concrete: Do not twist the saw blade. Do not let the blade spin in the cut, as this will increase wear on the bond. When cutting concrete with heavy rebar, use blades with soft metal segment bonds. Always use the required PPE (personal protection equipment).
What is saw cutting?
Sawcutting involves the formation of joints or breaks in a PCC mass (slab) by the use of mechanical cutting tools.
Where should a contraction joint be cut?
Proper joint location . Contraction joints must be cut over the internal dowel bar locations . If these locations are not marked, joints may not be cut at the dowel midpoints, which can result in excessive slab and dowel bar stresses.
What is a large saw used for?
Large saws . 50 – 55 kW in power and most commonly used for wet sawing applications. These saws are often used for longitudinal joints where their lack of maneuverability due to size is not critical.
What is a dry saw blade?
Dry sawing uses abrasive blades that are usually made from fiber reinforced silicone carbide or carborundum since these types of blades do not require water for cooling (ACPA, 1995). These abrasive blades have less cutting ability than diamond blades and are usually used on PCC with softer aggregate (ACPA, 1995 [1] ).
How much power does a span saw have?
Span saws (Figure 3) . 50 – 150 kW in power and are most commonly used for wet sawing applications. These are usually multi-bladed and used in high production jobs.
How many kW is a small saw?
Small saws . 6 – 13 kW in power and most commonly used for dry sawing applications. Lightweight saws (see Figure 2) used for early sawcuts are categorized as small saws.
Why do diamond tipped saw blades need to be cooled?
Diamond tipped blades will generate high amounts of heat when cutting and generally must be cooled by water to prevent the saw blade metal from overheating and melting. Water also prevents dust formation during sawing.
What is a saw cut jointer?
The Saw-Cut Joint Tool is a set comprised of a 36-inch two-handled chisel and a 6-inch jointer tool. The chisel goes into the concrete first and is slid back and forth by a worker who keeps the side of the tool aligned against a screed and the groove flush with a string line. The chisel cuts 1 1/4 inch into a slab.
Who makes saw cut joint tool?
The Saw Cut Joint Tool is manufactured by Tom Ralston in steel and bronze.
What is jointer tool?
The jointer tool follows with its 3/8-inch blade, cleaning up the cut and resmoothing the surface of the concrete. When used together, the two tools leave behind a line that is "perfectly clean.". Saw cuts tend to fray along the edges of the line. Saw cuts can also make a mess.
Can a saw cut joint be used on concrete?
The wheels of a cutting machine can leave marks on a fresh slab. Neither problem occurs when someone on kneeboards uses the Saw Cut Joint Tool set to hand-carve a straight line into wet concrete. Workers may be able to get onto the concrete to cut joints two to three hours after pouring.
Why use a saw cut on concrete?
Saw Cuts: Filled control joints help resist water and contaminates from damaging concrete floors. Saw cuts present more potential for floor damage than control joints because they are penetrating cuts at a 90-degree angle to the floor. Sharp edges are prone to chipping and cracking, especially on floors that are subject to abrasion ...
How thick should a saw cut be?
To be effective, saw cuts should be 1/4 of the slab thickness. While these joints are important to the structural integrity of the floor, they also have the potential for damage, performance, and safety problems.
What fillers do MJA companies use?
The MJA Company will inspect your control joints and recommend the appropriate fillers for your floor. Epoxies, polyeureas, and other products are available and should be matched to the floor and its usage.
What is a control joint?
Control Joints: Control joints that are placed at the time the concrete is installed and before the concrete cures are not as much of a problem as saw cuts that are done after the concrete has cured. In most cases, control joints that are created at the time of floor installation, have relatively smooth and rounded edges, ...
Why do you put contraction joints in concrete?
Since all concrete floors are subject to cracking, Control Joints (or contraction joints) should be placed in fresh concrete to create weakened planes that control the severity and pattern of cracks. In some cases, control joints are done after the concrete has cured and hardened by cutting lines in the floors with a concrete saw.
Why are sharp edges prone to chipping?
Sharp edges are prone to chipping and cracking, especially on floors that are subject to abrasion and impact from forklifts and heavy equipment. In the case of saw cuts, another problem is created when the top, smooth layer of the floor (Near-Surface Wear Zone) is removed.
Can control joints be filled?
However, even control joints can accumulate moisture, debris, chemicals, and be subject to increased impact. To prevent these problems, control joints can be filled to prevent contamination and create a smooth surface with is less vulnerable to wear and tear.
What saw cuts contraction joints?
Early entry saws cut a contraction joint before the concrete has a chance to begin shrinking. Husqvarna
How deep is a saw cut?
The saw-cut is typically 1 inch deep regardless of slab thickness—although even ¾-inch deep early-entry cuts can function properly. Keeping the skid plate and blades in good condition will improve the cut quality (less raveling). There is now an early entry saw made specifically for decorative work.
How are contraction joints formed?
Contraction joints are formed by saw cutting, by tooling a joint with a grooving tool, or by inserting a plastic strip into the concrete during finishing (zip-strip). Proper timing and depth of cut are essential. If you wait too long, the slab will crack where it wants to rather than where you want it to.
What is contraction joint?
Both isolation and construction joints are formed before the concrete is poured; contraction joints (or control joints) are "placed" in the fresh concrete before it has a chance to create its own joints—also known as cracks . What a contraction joint really is in the end is a crack in the slab that we force to follow a line of our own choosing.
What happens when a joint tees?
When a joint tees, a crack frequently forms on the other side of the joint. The jointing pattern may or may not be specified on your job. Take an active role in this plan to assure that joints are properly spaced and in the best locations for your work. For more information, read about Where to Place Control Joints.
How wide should jointed panels be?
Keep the length divided by the width of a panel (aspect ratio) no more than 1.5 (so if the panel is 12 feet long it should be no less than 8 feet wide). Avoid L- and T-shaped panels.
How long after concrete is a window cut?
The timing varies depending on the temperature and the relative humidity, but the window is generally 4 to 12 hours after concrete placement. The cut depth should be at least ¼ the thickness of the slab. For decorative work or smaller slabs, a regular dry-cut cut-off saw can be used.
