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Matthew Stuart, P.E., S.E., F.ASCE, SECB

Course Outline

Concrete slabs-on-grade are highly susceptible to cracking due to shrinkage. Construction and control joints are typically used to control crack location. Since it is not always desirable or practical to use a large number of closely spaced joints, reinforcing of the slab-on-grade allows for greater flexibility with joint spacing. Welded wire mesh or deformed bar reinforcement normally used in slabs-on-grade helps to control the width or growth of any cracks that may occur. This type of steel is sometimes called distribution reinforcement to differentiate it from structural reinforcement that is added to increase the load-carrying capacity of the slab.

This course includes a multiple choice quiz at the end.

Learning Objective

This course will enable the user to become familiar with the following methods of designing slab-on-grade "distribution" reinforcement;

1. Subgrade Drag Theory
2. Temperature Method
3. Concrete-to-Steel Ratio Method

This course will also familiarize the users with the three principal methods of reinforcing slab-on-grades;

1. Welded wire fabric
2. Deformed reinforcing bars
3. Post-tensioning cables

This course will also enable the user to have a fundamental understanding of the limitations of fiber reinforced concrete and the option to use shrinkage compensating concrete for slab-on-grade construction.

Course Introduction

This course will provide the user with an understanding of the subgrade drag theory and how it relates to the reinforcing of slab-on-grades as required to help control shrinkage cracking. Two other alternate design methods are also discussed relative to the sizing of "distribution" slab-on-grade reinforcement. Different types of reinforcing materials are also discussed including welded wire fabric, conventional deformed reinforcing bars and post-tensioning tendons.

Course Content

The course content is contained in the following PDF file:


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Course Summary

In the absence of properly located control or contraction joints in slab-on-grade construction the concrete will crack randomly as a result of the shrinkage of the material. Providing sawn joints in the slab promotes cracking at the joint itself thereby preventing random cracking of the slab. Spacing requirements for sawn control joints in unreinforced slab-on-grades are available through the recommendations of PCA. However, it is possible through the introduction of "distribution" reinforcement to increase the spacing of the contraction joints. Reinforcement can be provided in the form of welded wire fabric, deformed bars or post-tensioning tendons. The use of fiber reinforcement is not recommended to help control cracking in the absence of conventional reinforcing. Shrinkage compensating concrete (Type K) can also be used to help minimize the number of required control joints.

Related Links

For additional technical information related to this subject, please visit the following websites or web pages:

American Concrete Institute
Fiber Reinforced Concrete
Post Tensioned Slabs
Wire Reinforcement Institute
Slab Works


Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered professional engineer. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.