Sawing Contraction Joints - Husqvarna 390 Operator's Manual

SAWING CONTRACTION JOINTS

As concrete hydrates or cures and begins to set, it develops internal stresses which may cause ran-
dom cracks. Random cracks cast doubt on the quality and workmanship of the concrete. Contraction
joints are cut in concrete to relieve these stresses before they seek their own relief in the form of ran-
dom crack. The Soff-Cut Ultra Early Entry system controls random cracking through the early timing
of a saw cut at predetermined locations to create weakened planes in the concrete that subsequently
crack at the bottom of the cut to relieve stress. Husqvarna sawed contraction joints should be a mini-
mum of 1/8th the concrete depth and a minimum of 1" (25mm) deep. Contraction joints should be
sawn as soon as the concrete will support the weight of the saw and the operator without marking or
damaging the concrete. There are many possibilities for joint layout. Joint layout should be provided,
the saw contractor should submit a detailed joint layout for approval prior to cutting. Several factors
affect joint spacing including:
• Concrete thickness
• Type, amount and location of reinforcement
• Shrinkage potential of concrete-cement (type, quantity), aggregate (size, quantity, quality), water to
cement ratio,
admixtures, concrete temperature
• Base friction
• Slab restraints
• Layout of foundations, racks, pits, equipment pad, trenches, etc.
• Environmental factors - temperature, wind, humidity
• Methods and quality of concrete curing.
Generally, contraction joint patterns should divide slabs into approximate square panels per the recom-
mended spacing shown.
Concrete thickness, in. (mm)
3.5 (90)
4, 4.5 (100, 114)
5, 5.5 (125, 140)
6 (150) or greater
At all intersecting cross cuts, install Husqvarna joint protectors at each joint to prevent joint damage.
Install an additional joint protector where the right wheel will cross the joint to prevent concrete dam-
age.
RECOMMENDED CONTRACTION JOINT SPACING
Maximum spacing, ft. (m)
10 (3.0)
12 (3.6)
15 (4.5)
11
8 (2.4)