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Plastic Shrinkage Cracking

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Plastic Shrinkage Cracking Evaluation and Repair ACI 224.1R-93 Causes, Evaluation and Repair of Cracks in Concrete Structures ACI 224.1R-93 Chapter 1 Causes ... – PowerPoint PPT presentation

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Title: Plastic Shrinkage Cracking


1
Plastic Shrinkage Cracking
  • Evaluation and Repair

2
ACI 224.1R-93
  • Causes, Evaluation and Repair of Cracks in
    Concrete Structures

3
ACI 224.1R-93
  • Chapter 1 Causes Control
  • Chapter 2 Evaluation
  • Chapter 3 Methods of Crack Repair

4
ACI 224.1R-93
Typical Plastic Shrinkage Cracking. (Price 1982)
5
ACI 224.1R-93 Chapter 1, Section 1.2Cracking
of Plastic Concrete
  • Discusses Causes and Prevention ONLY!

6
ACI CP-10-Certification for Concrete
Technicians and Flatwork Finishers-
  • Discusses Causes and Prevention
  • ONLY!

7
NRMCAConcrete in Practice
  • If plastic shrinkage cracks should appear
    during final finishing, the finisher may be able
    to close them by refinishing.

8
NRMCAConcrete in Practice
  • Disclaimer
  • However, when this occurs, precautions, as
    described above, should be taken to avoid further
    cracking

9
PCA EB001 Design Control of
concrete Mixtures
  • If plastic shrinkage cracks should appear
    during finishing, striking each side of the crack
    with a float and refinishing can close the crack

10
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11
PCA EB001 Design Control of concrete
Mixtures
  • Disclaimer
  • However, the cracking may reoccur unless the
    causes are corrected

12
ACI 305R Hot Weather Concreting
  • Section 4.3.4
  • In relatively massive placements, revibration
    before floating can sometimes close this type of
    cracking.

13
PCA EB001
Fig. 11-11.
14
ACI 224.1R-93
Typical Plastic Shrinkage Cracking. (Price 1982)
15
Much more serious cracking!
16
PCA EB001
Fig. 11-13.
17
ACI 224.1R-93Chapter 2
  • Evaluation of Cracks in Hardened Concrete

18
ACI 224.1R-93 Chapter 2
  • Identify Location and Extent of Cracking

19
Typical Plastic Shrinkage Cracking
20
Much more serious cracking!
21
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22
ACI 224 Chapter 2
  • 2. Determine functionality
  • - Movement
  • - Structural
  • Maintenance issue
  • Cosmetic

23
ACI 224 Chapter 2
  • 2.2 Map the cracks!

24
ACI 224.1R-93
  • Fig. 2.1-Comparator for measuring crack widths
    Courtesy of Edmound Scientific Co.

25
  • Crack Comparitor Card

26
ACI 224 Chapter 3
  • Methods of Crack Repair
  • in Hardened Concrete

27
ACI 224 Chapter 3
  • 3.2 Epoxy injection
  • - Bonds cracks as narrow as 0.002 in.
  • - Provides fixity
  • - Original cause must be addressed
  • - Typically deferred to specialist

28
ACI 503.7-07
  • Specification for Crack Repair by Epoxy Injection

29
ACI 224 Chapter 3
  • 3.3 Routing and sealing
  • - Clean cracks
  • - Enlarge crack along exposed face
  • - Fill and seal with suitable joint sealant
  • - Not suitable for structural repairs

30
ACI 224.1R-93
Groove cut wlth saw or chipping tools7
Fig. 3.1-Repair of crack by muting and sealing
(Johnson 1965)
31
ACI 224.1R-93
  • If large enough, treat as an induced crack
  • Sawcut and fill

32
ACI 224.1R-93 Chapter 3
With Bond Breaker
Crack Closed
No Bond Breaker
Fig. 3.2-Effect of bond breaker
See ACI 504R Re. Aspect Ratio
33
ACI 224 Chapter 3
  • 3.11 Polymer Impregnation
  • Methyl Methacrylate
  • Flood surfaces
  • Heat to polymerize, or
  • Use a catalyst to polymerize

34
ACI 224 Chapter 3
  • 3.12.1 Surface Treatments
  • - Low viscosity penetrating resins
  • - Urethanes
  • - Epoxies
  • - Polyesters
  • - Acrylics

35
ACI 224 Chapter 3
  • 3.12.2 Overlays
  • - Polymer modified PCC
  • - Styrene Butadiene
  • - Bridge decks
  • - Acrylic latex
  • - Interior toppings
  • - Pool decks
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