Chapter 4. Working with Silica-Fume Concrete  Conducting a Test Placement  Transporting, Placing, and Consolidating  Finishing Flatwork  Finishing.

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Presentation transcript:

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

Conducting a Test Placement Chapter Outline

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

Cohesive silica- fume concrete -- OK to increase slump

Conducting a test placement

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

Silica-fume concrete requires thorough consolidation

Finishing Silica-Fume Concrete Flatwork Chapter Outline

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

Under Finish Silica- Fume Concrete Use the “One-Pass” Technique

One-Pass Finishing  Screed  Float  Texture  Cure Protect, Protect!

One-pass finishing

Float and brooming tool

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

Finishing Silica-Fume Concrete Bridge Decks Chapter Outline

Tined surface

Preventing Plastic Shrinkage Cracking Chapter Outline

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

Plastic shrinkage cracking

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

Good fogging

Improper fogging

Evaporation retarders work well but are frequently misused

Curing Silica-Fume Concrete Chapter Outline

How Important is Curing Silica Fume Concrete?

“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

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

Applying curing compound while concrete is still fresh

Moist curing after concrete hardens

Don’t forget winter protection

End of Chapter 4 Main Outline