It is recommended to start saw cuts on or at the center of column lines . 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.
Is it too late to cut control joints?
Cutting too early can mark the pavement surface as well as cause joint raveling. Late sawing can result in random concrete cracks . ... Once cutting starts, it has to continue until the joints are finished and before the concrete surface temperature begins to fall.
When should I cut my control joints?
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 control joints?
The control joint could be spaced every two floors , however, the size of the shelf angle and the width of the joint would have to be larger. A 3/8 to 1/2 inch (10- 12mm) wide joint is satisfactory for control joints every 10 ft.
How often should you cut concrete?
Joints should be sawed as soon as the concrete will withstand the energy of sawing without raveling or dislodging aggregate particles. For most concrete mixtures, this means sawing should be completed within the first six to 18 hours and never delayed more than 24 hours .
How big can a concrete slab be without expansion joints?
Rule #1 – Keep joints as square as possible. Rule #2 – In order to prevent intermediate cracking, space joints (in feet) no more than 2 – 3 times the slab thickness (in inches) .
Are control joints necessary?
There is a reason control joints are considered essential for whatever projects you have in design. Thermal expansion and contraction will occur in buildings – that’s a given – and control joints help prevent resulting cracks and damage .
What is the difference between expansion joints and control joints?
In building materials, a control joint is used to control cracking while an expansion joint is designed to handle structural movement. ... A control joint can be formed during placement of the building material or cut after the material is placed.
What is the difference between construction joint and 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.
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 brick walls need expansion joints?
Expansion joints must be located so that the structural integrity of the brickwork is not compromised . A control joint determines the location of cracks in concrete or concrete masonry construction due to volume changes resulting from shrinkage.
What is the distance between expansion joints?
Expansion joint
Maximum spacing of expansion joints range from 25-27 m in jointed reinforced concrete slabs, and from 40 m (for slabs <230 mm thick) to 60 m (for slabs >230 mm thick) in unreinforced concrete.
Why do they cut lines in concrete?
To prevent sidewalks from cracking in random spots and breaking apart, builders make lines in sidewalks. ... The technical term for sidewalk lines is contraction joints. Contraction joints are placed in fresh concrete before the concrete dries and has a chance to create its own joints, which we call cracks.
Do concrete driveways need expansion joints?
Every concrete slab, inside (basements, garages, etc.) or outside (driveways, patios, entries, etc.) are required to have joints every eight feet horizontally and vertically . Expansion Joints provide space between concrete slabs as a buffer for expansion on hot days and contraction when it is cold.
How deep should relief cuts be in concrete?
A good rule of thumb is to make your cut 1⁄4 the thickness of your concrete . If 1⁄4 of your slab’s thickness, doesn’t reach 1” make sure you still cut at least a 1” depth.
Do you need water when cutting concrete?
Water not only helps cool and lubricate the blade but also keeps the dust down . These cut the fastest and cleanest, but they require a special saw that can both distribute water and be safely used around it.
