CRSI - WRI |
ENGINEERING
DATA REPORT NUMBER 37-
TECH FACTS TF 701 |
REINFORCING STEEL IN SLABS-ON-GRADE |
 CONCRETE
REINFORCING STEEL INSTITUTE
933 N. Plum Grove Rd., Schaumburg, Illinois 60173-4758 |
 WIRE
REINFORCEMENT INSTITUTE
110 1 Connecticut Ave. N.W, Suite 700
Washington, DC 20036-4303 |
 |
 |
| WELDED
WIRE FABRIC |
REINFORCING
BARS |
INTRODUCTION
The phrase slab-on-grade, as commonly used
in practice, covers a number of practical slab applications. Included are industrial and
commercial floors, residential floors, parking lots, pavements, airport slabs and other
practical uses of ground-supported concrete slabs. This report applies to all of these
applications.
Reinforcing steel, in
the form of welded wire fabric or deformed bars in both directions, may be placed in the
slab-on-grade for a number of reasons. This form of reinforcement adds to the strength of
the slab, acts as crack control including the well-known restraint of shrinkage (as well
as temperature) effects, reduces future maintenance, and generally helps produce a higher
quality concrete slab. A complete listing of advantages is included elsewhere in this
report.
Reinforcing bars or
welded wire fabric (WWF) functions as reinforcement because such steel is supported and
thus placed in a specific position in the slab prior to the placement of the concrete.
Visual inspection verifies that the reinforcement is properly positioned and will have the
positive effects desired.
When reinforcing bars
are specified, they are to be placed in two layers (one layer directly in contact with the
other), with bars running in two perpendicular directions, tied together so as to maintain
the spacing requirements, and they must be supported. When welded wire fabric (deformed or
plain) is specified, it should have sufficiently large wire diameters so as to be
structurally stiff enough to remain in its proper position during construction, with a
wire spacing selected for construction stability and convenience, and the WWF must be
supported.
ADVANTAGES
There are numerous advantages that result from placing reinforcing bars or
welded wire fabric in a slab-on-grade. The following list shows what reinforcement can do
for the slab. Some of these can be achieved in no other way:
• Controls Cracking
Reinforcement within a slab prevents cracks from opening and becoming wide and
objectionable. These cracks may be due to drying shrinkage or due to externally applied
loadings. When these cracks are kept tight, aggregate interlock will still exist and
faulting will not occur. Cracks are frequently kept so tight as to be difficult to see.
• Allows Increased Joint
Spacings
The spacings of construction and control joints may be increased when distributed
reinforcement is used. The increase can vary from 'slight' to 'substantial' depending upon
the concept of design and the intended performance of the slab. The subgrade drag equation
(explained in design example) has been used to relate wider joint spacings with given
areas of reinforcing bars or welded wire fabric.
© Copyright 1991 by the Concrete Reinforcing Steel Institute
