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Discover tips trick and info about the world's most versatile building product with Chaney
Enterprises Concrete Briefs.
There are two types of concrete. Concrete that has cracked and concrete that hasn't
cracked yet.
In exterior flat work, a stable uniform base and a good concrete curing are essential.
But most cracks that we see could be controlled by quality joint planning and construction.
Joints create a plane of weakness in the concrete directing the concrete where to crack. There
are three types of joints, contraction joints, construction joints and isolation joints.
The most common are contraction joints which control cracks caused by restrained shrinkage,
loads and other stresses. The joint depth should be at least one-quarter of the slab
thickness. A narrow joint width between on tenth to one eighth inches wide is a common
way to avoid joint sealing.
Concrete naturally wants to crack in squares the jointing pattern should be cut as close
to squares as possible. Where it is not possible the length of the panel should not exceed
more than twenty five percent of the width. For irregular shaped panels where the angles
would be less than forty five degrees, ore-cut wire mesh or fibers may be used to control
cracking.
Per the American Concrete Institute three thirty guide for the parking lot design, we
do not recommend welded wire mesh be widely distributed throughout the slab. If wire mesh
holds the concrete together and joints give the concrete a place to separate, the two
practices are actually fighting each other and will only serve to increase labor and
material costs.
Joint spacing is determined by slab thickness. Generally the smaller the joint spacing the
better. Maximum spacing is based upon the slab thickness and should not exceed thirty
times the slab thickness. Recommended spacing is about 30 percent closer is possible.
For unrestrained edges, tie bars should be used in the first joint from the slab edge
to avoid the risk of the panel becoming separated from the slab. To be safe, abutting asphalt
should be considered an unrestrained edge. Unrestrained edges should be thickened to
help with load bearing.
Construction joints are joints where the construction needs to stop such as between work days. The
adjacent slab should be tied together or thickened due to load transfer from one slab to another.
Isolation joints are used to separate the pavement from other structures or fixed object
within or abutting the paved area. This is most common in sign posts, drains and utility
access areas.
No matter what joints you are you using. Good planning will go a long way to make sure the
cracks happen where you want to. A complete guide to jointing is available on our website
at ChaneyEnterprises.com/ConcreteParking.
Thank you for watching this episode of concrete briefs from Chaney Enterprises.