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.