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Chapter 4. Working with Silica-Fume Concrete

Chapter 4. Working with Silica-Fume Concrete

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Chapter 4. Working with Silica-Fume Concrete

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  1. Chapter 4. Working with Silica-Fume Concrete • Conducting a Test Placement • Transporting, Placing, and Consolidating • Finishing Flatwork • Finishing Bridge Decks • Preventing Plastic-Shrinkage Cracking • Curing

  2. Conducting a Test Placement Chapter Outline

  3. Remember:Silica-fume concrete is more cohesive and less prone to segregationTo improve workability, increase slump by about 2 in. (50 mm)

  4. Cohesive silica-fume concrete -- OK to increase slump

  5. Conducting a test placement

  6. Transporting, Placing, and Consolidating Silica-Fume Concrete Chapter Outline

  7. Silica-fume concrete requires thorough consolidation

  8. Finishing Silica-Fume Concrete Flatwork Chapter Outline

  9. Click on the icon above to play a video on finishing silica-fume concrete

  10. Under Finish Silica-Fume ConcreteUse the “One-Pass” Technique

  11. One-Pass Finishing • Screed • Float • Texture • Cure Protect, Protect, Protect!

  12. One-pass finishing

  13. Float and brooming tool

  14. Broomed surface -- all that is required for a parking structure

  15. Finishing Silica-Fume Concrete Bridge Decks Chapter Outline

  16. Tined surface

  17. Preventing Plastic Shrinkage Cracking Chapter Outline

  18. What is Plastic Shrinkage Cracking? Cracking that occurs in the surface of fresh concrete soon after it is placed and while it is still plastic. -- ACI 116R

  19. Plastic shrinkage cracking

  20. Silica fume concrete does not bleed and is more susceptible to plastic shrinkage cracking

  21. Good fogging

  22. Improper fogging

  23. Evaporation retarders work well but are frequently misused

  24. Curing Silica-Fume Concrete Chapter Outline

  25. How Important is Curing Silica Fume Concrete?

  26. “If silica-fume concrete mixtures are given 7 days of continuous moist curing, then there is no association between silica fume content and cracking.” -- Whiting and Detwiler NCHRP Report 410

  27. “It is recommended that a minimum of 7 days continuous moist curing be specified.” -- Whiting and Detwiler NCHRP Report 410

  28. Applying curing compound while concrete is still fresh