To get air bubbles out of already laid concrete it is best to ______.

To get air bubbles out of already laid concrete it is best to ______.

• A. Screed
• B. Air Entrain
• C. Vibrate
• D. Add Cement

Answer: (C)

Consolidating the concrete to eliminate trapped voids is what reduces air bubbles. Vibrating the mix creates movement that allows the cement paste to flow into gaps around the aggregates and pushes air pockets upward to escape, yielding a denser, stronger slab with fewer voids. Screeding focuses on leveling and finishing the surface, not on removing internal air voids. An air-entraining admixture is used to create tiny, controlled air voids for freeze–thaw durability, not to flush out existing bubbles. Adding more cement would change the mix’s proportions and workability rather than specifically remove air pockets. Use the vibrator appropriately to avoid over-vibration and potential segregation.

Consolidating the concrete to eliminate trapped voids is what reduces air bubbles. Vibrating the mix creates movement that allows the cement paste to flow into gaps around the aggregates and pushes air pockets upward to escape, yielding a denser, stronger slab with fewer voids. Screeding focuses on leveling and finishing the surface, not on removing internal air voids. An air-entraining admixture is used to create tiny, controlled air voids for freeze–thaw durability, not to flush out existing bubbles. Adding more cement would change the mix’s proportions and workability rather than specifically remove air pockets. Use the vibrator appropriately to avoid over-vibration and potential segregation.