Description

Given the high flowability and relatively fast casting rate of self-consolidating concrete (SCC), such concrete can exert high form pressure. Accurate assessment of form pressure is necessary from safety and economic points of view. The maximum form pressure and pressure decay are dependent on the structural buildup of the concrete at rest following placement, as well as on the placement parameters. The structural buildup at rest is affected by the thixotropy of the mixture. This report presents information on key parameters, including constituent materials; mixture proportioning; and casting parameters such as the casting rate, concrete temperature, and reinforcement percentage, affecting thixotropy and SCC form pressure. Prediction models available for estimating SCC form pressure are presented. Findings from two round-robin field studies conducted to validate these models are also discussed. This report should be of interest to concrete professionals, including concrete suppliers and formwork designers, because it covers: 1) the influence of SCC proportions and casting parameters on form pressure; 2) means to estimate formwork pressure with examples; and 3) techniques to measure formwork pressure in field applications.

Keywords:

form pressure; lateral pressure; self-consolidating concrete; structural buildup at rest; thixotropy.

Document Details

Author: ACI Committee 237

Pages: 32

ISBN: 9781641951456

Categories: Consolidation, Formwork, Reinforcement

Formats: Printed Document or Protected PDF/Web View

Table of Contents

CHAPTER 1—INTRODUCTION, p. 2

1.1—Introduction, p. 2

1.2—Scope, p. 3

1.3—Use of U.S. Customary Units in this report, p. 3

CHAPTER 2—NOTATION AND DEFINITIONS, p. 4

2.1—Notation, p. 4

2.2—Definitions, p. 4

CHAPTER 3—THIXOTROPY AND FORM PRESSURE, p. 4

3.1—Thixotropy, p. 4

3.2—Thixotropy test methods, p. 5

3.3—Influence of thixotropy on form pressure, p. 9

CHAPTER 4—EFFECT OF MIXTURE CHARACTERISTICS ON FORM PRESSURE, p. 11

4.1—Introduction, p. 11

4.2—Binder constituents and content, p. 11

4.3—Water content, p. 12

4.4—Aggregate characteristics, p. 12

4.5—Chemical admixtures, p. 13

CHAPTER 5—EFFECT OF CASTING PARAMETERS ON FORM PRESSURE, p. 14

5.1—Introduction, p. 14

5.2—SCC mixture temperature, p. 14

5.3—Casting rate, p. 14

5.4—Formwork characteristics, p. 15

5.5—Reinforcement percentage, p. 16

CHAPTER 6—PREDICTION MODELS FOR SCC FORM PRESSURE, p. 17

6.1—Introduction, p. 17

6.2—Model by Gardner et al. (2012), p. 17

6.3—Model by Khayat and Omran (2010b), p. 17

6.4—Model by Tejeda-Dominguez et al. (2005), p. 18

6.5—Model by Ovarlez and Roussel (2007), p. 19

CHAPTER 7—MEASUREMENT TECHNIQUES, p. 19

7.1—Strain-gauge-based pressure sensor setup, p. 19

7.2—Pressure reading graph example, p. 21

7.3—Precautions and maintenance when measuring form pressure, p. 21

CHAPTER 8—FIELD VALIDATION OF PREDICTION MODELS, p. 21

8.1—Stockholm, Sweden, 2012, p. 21

8.2—Toronto, Canada, 2014, p. 23

8.3—Validation of models, p. 26

8.4—Considerations for formwork design, p. 27

CHAPTER 9—SUMMARY, p. 27

CHAPTER 10—REFERENCES, p. 27

Authored references, p. 27

APPENDIX A—EXAMPLE CALCULATIONS, p. 29

A1—Calculation of form pressure using model by Gardner et al. (2012), p. 30

A2—Calculation of form pressure using model by Khayat and Omran (2010b), p. 30

A3—Calculation of form pressure using model by Tejeda-Dominguez et al. (2005), p. 31

A4—Calculation of form pressure using model by Ovarlez and Roussel (2007), p. 31

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