TM Plastic Shrinkage

35
Plastic Shrinkage Cracking  Evaluation and Repair 

Transcript of TM Plastic Shrinkage

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Plastic Shrinkage

Cracking 

Evaluation and Repair 

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ACI 224.1R-93

Causes, Evaluation and Repair of Cracks in Concrete Structures

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ACI 224.1R-93

Chapter 1 ± Causes & Control

Chapter 2 ± Evaluation

Chapter 3 ± Methods of Crack Repair 

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ACI 224.1R-93

Typical Plastic Shrinkage Cracking. (Price 1982)

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 ACI 224.1R-93Chapter 1, Section 1.2

³Cracking of Plastic Concrete´

Discusses Causes and Prevention ONLY! 

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 ACI CP-10

-Certification for Concrete Technicians

and Flatwork Finishers-

Discusses Causes and Prevention

ONLY! 

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NRMC A

Concrete in Practice

³If plastic shrinkage cracks shouldappear during final finishing, the

finisher may be able to close them by 

refinishing.´

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NRMC A

Concrete in Practice

Disclaimer 

³However, when this occurs, precautions,

as described above, should be taken to

avoid further cracking´

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PCA EB001Design & Control of concrete Mixtures

³If plastic shrinkage cracks should

appear during finishing, striking each 

side of the crack with a float andrefinishing can close the crack´

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PCA EB001

Design & Control of concrete Mixtures

Disclaimer 

³However, the cracking may reoccur 

unless the causes are corrected´

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ACI 305R

Hot Weather Concreting

Section 4.3.4

In relatively massive placements,

revibration before floating can sometimesclose this type of cracking.

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PCA EB001

Fig. 11-11.

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ACI 224.1R-93

Typical Plastic Shrinkage Cracking. (Price 1982)

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Much more serious cracking!

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Fig. 11-13.

PCA EB001

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 ACI 224.1R-93

Chapter 2

E valuation of Cracks in

Hardened Concrete

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 ACI 224.1R-93

Chapter 2

1. I dentify Location and Ex tent of Cracking 

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Typical Plastic Shrinkage Cracking

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Much more serious cracking!

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 ACI 224

Chapter 2

2 . Determine functionality - Movement 

- Structural

- Maintenance issue

- Cosmetic

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 ACI 224

Chapter 2

2 .2 Map the cracks! 

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 ACI 224.1R-93

F ig. 2.1-Comparator for measuring crack 

widths Courtesy of 

Edmound Scientific 

Co.

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Crack Comparitor Card 

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 ACI 224

Chapter 3

M ethods of Crack Repair 

in Hardened Concrete

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 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

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 ACI 503.7-07

Specification for Crack Repair by Epoxy Injection

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 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

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Groove cut wlth saw

or chipping tools7

 ACI 224.1R-93

F ig . 3.1- Repair of crack by muting and sealing 

(Johnson 1965)

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 ACI 224.1R-93

If large enough, treat as an induced crack

Sawcut and fill

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Crack Closed No Bond Breaker   With Bond Breaker 

F ig . 3.2 -E ffect of bond breaker 

 ACI 224.1R-93

Chapter 3

See ACI 504R Re.  Aspect Ratio

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 ACI 224

Chapter 3

3.11 Polymer Impregnation

Methyl Methacr ylate ±Flood surfaces

 ±Heat to polymerize, or 

 ±Use a catalyst to polymerize

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 ACI 224

Chapter 3

3.12.1 Surface Treatments

- Low viscosity penetrating resins

- Urethanes

- Epoxies

- Polyesters- Acr ylics

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 ACI 224

Chapter 3

3.12.2 Overlays

- Polymer modified PCC

- Styrene Butadiene

- Bridge decks

- Acr ylic latex- Interior toppings

- Pool decks