Concrete Repair & Restoration Flashcards

What is the primary purpose of applying a bonding agent before placing repair mortar on existing concrete?

Answer: To improve adhesion between old and new concrete

Bonding agents create a chemical or mechanical link between the existing substrate and the repair material to prevent delamination.

When using dry-pack mortar for repair, the water-to-cement ratio should be:

Answer: Just enough to ball in your hand without crumbling or releasing water

Dry-pack mortar uses a very low w/c ratio; the mix should barely hold together when squeezed, minimizing shrinkage.

Alkali-silica reaction (ASR) in concrete is best identified by:

Answer: Map cracking with gel exudate around aggregate particles

ASR produces a characteristic map or crazing crack pattern with silica gel oozing around reactive aggregates.

Which repair method is most appropriate for filling wide, dormant horizontal cracks in a concrete floor slab?

Answer: Dry-pack mortar rodded into the crack

Wide dormant cracks in horizontal slabs are best repaired by routing to a uniform shape and filling with dry-pack mortar or rigid filler.

The minimum repair area depth recommended by ACI 546 for a partial-depth patch is generally:

Answer: 1 inch

ACI 546 recommends a minimum partial-depth repair of 1 inch to ensure adequate bond and material integrity.

Before placing a concrete overlay, the existing surface should be profiled to a minimum CSP (Concrete Surface Profile) of:

Answer: CSP 3–5 (medium scarification)

Overlays require moderate surface profile (CSP 3–5) to provide mechanical interlock without excessively damaging the substrate.

Which condition would cause a repair patch to fail most rapidly?

Answer: Placing repair material over a dry, dusty surface with no bond coat

A dry, dusty substrate without a bonding agent prevents adhesion and leads to early delamination of the patch.