Husqvarna 2000 manual Sawing Contraction Joints, Recommended Contraction Joint Spacing

SAWING CONTRACTION JOINTS

As concrete hydrates or cures and begins to set, it develops internal stresses which may cause random 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 random 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 minimum 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 cut- ting. 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 recommended spacing shown.

	RECOMMENDED CONTRACTION JOINT SPACING
Concrete thickness, in. (mm)		Maximum spacing, ft. (m)
3.5 (90)		8 (2.4)
4, 4.5	(100, 114)	10 (3.0)
5, 5.5	(125, 140)	12 (3.6)
6 (150) or greater		15 (4.5)

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 damage.

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