Which factor is most important when applying concrete to concrete?

Which factor is most important when applying concrete to concrete?

• A. Set Time
• B. Bond
• C. Workability
• D. Color

Answer: (B)

When placing fresh concrete against an existing surface, the most important factor is the bond between the two layers. This bond lets the new concrete adhere and transfer loads across the interface, so the two pours act as a single structural element rather than two unconnected slabs. Achieving good bond depends on proper surface preparation: cleaning and removing laitance, roughening the old surface to create mechanical keying, controlling moisture (not too wet or dry), and using appropriate bonding agents or a compatible mix if needed. If the bond isn’t solid, you’ll get cold joints, delamination, or cracking at the interface, regardless of how doable the concrete is to place or how fast it sets. Set time, workability, and color matter in other ways—set time affects early strength and finishing, workability influences how easily you place and consolidate, and color is cosmetic—so they don’t determine the structural integrity of the joint like bond does.

When placing fresh concrete against an existing surface, the most important factor is the bond between the two layers. This bond lets the new concrete adhere and transfer loads across the interface, so the two pours act as a single structural element rather than two unconnected slabs. Achieving good bond depends on proper surface preparation: cleaning and removing laitance, roughening the old surface to create mechanical keying, controlling moisture (not too wet or dry), and using appropriate bonding agents or a compatible mix if needed. If the bond isn’t solid, you’ll get cold joints, delamination, or cracking at the interface, regardless of how doable the concrete is to place or how fast it sets. Set time, workability, and color matter in other ways—set time affects early strength and finishing, workability influences how easily you place and consolidate, and color is cosmetic—so they don’t determine the structural integrity of the joint like bond does.