Title: Plastic Shrinkage Cracking
1Plastic Shrinkage Cracking
2ACI 224.1R-93
- Causes, Evaluation and Repair of Cracks in
Concrete Structures
3ACI 224.1R-93
- Chapter 1 Causes Control
- Chapter 2 Evaluation
- Chapter 3 Methods of Crack Repair
4ACI 224.1R-93
Typical Plastic Shrinkage Cracking. (Price 1982)
5ACI 224.1R-93 Chapter 1, Section 1.2Cracking
of Plastic Concrete
- Discusses Causes and Prevention ONLY!
6ACI CP-10-Certification for Concrete
Technicians and Flatwork Finishers-
- Discusses Causes and Prevention
- ONLY!
7NRMCAConcrete in Practice
- If plastic shrinkage cracks should appear
during final finishing, the finisher may be able
to close them by refinishing.
8NRMCAConcrete 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(No Transcript)
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.
13PCA EB001
Fig. 11-11.
14ACI 224.1R-93
Typical Plastic Shrinkage Cracking. (Price 1982)
15Much more serious cracking!
16PCA EB001
Fig. 11-13.
17ACI 224.1R-93Chapter 2
-
- Evaluation of Cracks in Hardened Concrete
18ACI 224.1R-93 Chapter 2
-
- Identify Location and Extent of Cracking
19Typical Plastic Shrinkage Cracking
20Much more serious cracking!
21(No Transcript)
22ACI 224 Chapter 2
-
- 2. Determine functionality
- - Movement
- - Structural
- Maintenance issue
- Cosmetic
23ACI 224 Chapter 2
24ACI 224.1R-93
- Fig. 2.1-Comparator for measuring crack widths
Courtesy of Edmound Scientific Co.
25 26ACI 224 Chapter 3
-
- Methods of Crack Repair
- in Hardened Concrete
27ACI 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
28ACI 503.7-07
- Specification for Crack Repair by Epoxy Injection
29ACI 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
30ACI 224.1R-93
Groove cut wlth saw or chipping tools7
Fig. 3.1-Repair of crack by muting and sealing
(Johnson 1965)
31ACI 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
33ACI 224 Chapter 3
- 3.11 Polymer Impregnation
- Methyl Methacrylate
- Flood surfaces
- Heat to polymerize, or
- Use a catalyst to polymerize
34ACI 224 Chapter 3
- 3.12.1 Surface Treatments
- - Low viscosity penetrating resins
- - Urethanes
- - Epoxies
- - Polyesters
- - Acrylics
35ACI 224 Chapter 3
- 3.12.2 Overlays
- - Polymer modified PCC
- - Styrene Butadiene
- - Bridge decks
- - Acrylic latex
- - Interior toppings
- - Pool decks