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This guide presents information on the design of slabs-on-ground, primarily industrial floors. It addresses the planning, design, and detailing of slabs. Background information on design theories is followed by discussion of the types of slabs, soil-support systems, loadings, and jointing. Design methods are given for unreinforced concrete, reinforced concrete, shrinkage-compensating concrete, post-tensioned concrete, fiber-reinforced concrete slabs-on-ground, and slabs-on-ground in refrigerated buildings, followed by information on shrinkage and curling.

Advantages and disadvantages of these slab design methods are provided, including the ability of some slab designs to minimize cracking and curling more than others. Even with the best slab designs and proper construction, it is unrealistic to expect crack-free and curl-free floors. Every owner should be advised by the designer and contractor that it is normal to expect some cracking and curling on every project. This does not necessarily reflect adversely on the adequacy of the floor’s design or quality of construction. Design examples are given.

Keywords: curling; design; floors-on-ground; grade floors; industrial floors; joints; load types; post-tensioned concrete; reinforcement (steel, fibers); shrinkage; shrinkage-compensating; slabs; slabs-on-ground; soil mechanics; warping.

Contents: Chapter 1—Introduction, p. 360R-3

1.1—Purpose and scope

1.2—Work of ACI Committee 360 and other relevant committees

1.3—Work of non-ACI organizations

1.4—Design theories for slabs-on-ground

1.5—Construction document information

1.6—Further research

Chapter 2—Definitions, p. 360R-5

2.1—Definitions

Chapter 3—Slab types, p. 360R-6

3.1—Introduction

3.2—Slab types

3.3—General comparison of slab types

3.4—Design and construction variables

3.5—Conclusion

Chapter 4—Soil support systems for slabs-on-ground, p. 360R-8

4.1—Introduction

4.2—Geotechnical engineering reports

4.3—Subgrade classification

4.4—Modulus of subgrade reaction

4.5—Design of slab-support system

4.6—Site preparation

4.7—Inspection and site testing of slab support

4.8—Special slab-on-ground support problems

Chapter 5—Loads, p. 360R-18

5.1—Introduction

5.2—Vehicular loads

5.3—Concentrated loads

5.4—Distributed loads

5.5—Line and strip loads

5.6—Unusual loads

5.7—Construction loads

5.8—Environmental factors

5.9—Factors of safety

Chapter 6—Joints, p. 360R-22

6.1—Introduction

6.2—Load-transfer mechanisms

6.3—Sawcut contraction joints

6.4—Joint protection

6.5—Joint filling and sealing

Chapter 7—Design of unreinforced concrete slabs,p. 360R-31

7.1—Introduction

7.2—Thickness design methods

7.3—Shear transfer at joints

7.4—Maximum joint spacing

Chapter 8—Design of slabs reinforced for crack-width control, p. 360R-34

8.1—Introduction

8.2—Thickness design methods

8.3—Reinforcement for crack-width control only

Chapter 9—Design of shrinkage-compensating concrete slabs, p. 360R-34

9.1—Introduction

9.2—Thickness determination

9.3—Reinforcement

9.4—Other considerations

Chapter 10—Design of post-tensioned slabs-on-ground, p. 360R-38

10.1—Introduction

10.2—Applicable design procedures

10.3—Slabs post-tensioned for crack control

10.4—Industrial slabs with post-tensioned reinforcement for structural support

Chapter 11—Fiber-reinforced concrete slabs-on-ground, p. 360R-40

11.1—Introduction

11.2—Synthetic fiber reinforcement

11.3—Steel fiber reinforcement

Chapter 12—Structural slabs-on-ground supporting building code loads, p. 360R-44

12.1—Introduction

12.2—Design considerations

Chapter 13—Design of slabs for refrigerated facilities, p. 360R-44

13.1—Introduction

13.2—Design and specification considerations

13.3—Temperature drawdown

Chapter 14—Reducing effects of slab shrinkage and curling, p. 360R-45

14.1—Introduction

14.2—Drying and thermal shrinkage

14.3—Curling and warping

14.4—Factors that affect shrinkage and curling

14.5—Compressive strength and shrinkage

14.6—Compressive strength and abrasion resistance

14.7—Removing restraints to shrinkage

14.8—Base and vapor retarders/barriers

14.9—Distributed reinforcement to reduce curling and number of joints

14.10—Thickened edges to reduce curling

14.11—Relation between curing and curling

14.12—Warping stresses in relation to joint spacing

14.13—Warping stresses and deformation

14.14—Effect of eliminating sawcut contraction joints with post-tensioning or shrinkage-compensating concrete

14.15—Summary and conclusions

Chapter 15—References, p. 360R-53

15.1—Referenced standards and reports

15.2—Cited references

Appendix 1—Design examples using Portland Cement Association method, p. 360R-58

A1.1—Introduction

A1.2—The PCA thickness design for single-axle load

A1.3—The PCA thickness design for slab with post loading

A1.4—Other PCA design information

Appendix 2—Slab thickness design by Wire Reinforcement Institute method, p. 360R-60

A2.1—Introduction

A2.2—The WRI thickness selection for single-axle wheel load

A2.3—The WRI thickness selection for aisle moment due to uniform loading

Appendix 3—Design examples using Corps of Engineers’ charts, p. 360R-63

A3.1—Introduction

A3.2—Vehicle wheel loading

A3.3—Heavy lift truck loading

Appendix 4—Slab design using post-tensioning, p. 360R-63

A4.1—Design example: Post-tensioning to minimize cracking

A4.2—Design example: Equivalent tensile stress design

Appendix 5—Design example using shrinkagecompensating concrete, p. 360R-65

A5.1—Introduction

A5.2—Example selecting the optimum amount of reinforcement to maximize the compressive stress in the

concrete where the slab thickness, the joint spacing, and prism expansion are known

Appendix 6—Design examples for steel FRC slabs-on- ground using yield line method, p. 360R-66

A6.1—Introduction

A6.2—Assumptions and design criteria

Appendix 7—Construction document information,p. 360R-67

A7.1—Introduction

A7.2—Example design criteria

A7.3—Typical details

Conversion factors, p. 360R-72