Concrete Repair & Restoration Flashcards
7 cards from real ACI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Concrete Repair & Restoration flashcards as text
The term 'delamination' in a concrete slab on grade most often results from:
Answer: Finishing operations that seal the surface while bleed water is still rising
Premature finishing traps rising bleed water and air beneath a dense surface layer, creating a weak horizontal plane that delaminates under traffic.
When electrochemical chloride extraction (ECE) is used on reinforced concrete, the process:
Answer: Drives chloride ions out of the concrete toward an external anode in an electrolyte
ECE uses an impressed electrical current to migrate chloride ions from the steel reinforcement toward a temporary external anode.
Fly ash used as a repair material ingredient primarily improves:
Answer: Long-term durability by reducing permeability and reacting with calcium hydroxide
Fly ash undergoes pozzolanic reaction with calcium hydroxide to form additional C-S-H, densifying the paste and reducing permeability.
A repair mortar with a coefficient of thermal expansion significantly different from the parent concrete will:
Answer: Develop stress concentrations at the repair interface during temperature changes
Mismatched thermal expansion coefficients cause differential movement at repair boundaries, leading to debonding and cracking.
What does the term 'full-depth repair' mean on a concrete pavement project?
Answer: Removing concrete the full depth of the slab thickness
Full-depth repair removes the entire slab thickness (not just the top layer) and replaces it with new concrete.
When installing load-transfer dowels in a full-depth concrete pavement repair, the dowels should be placed:
Answer: At mid-depth of the slab and parallel to the direction of traffic
Dowels must be at mid-depth and aligned parallel to traffic to transfer vertical shear loads across the joint without restraining slab movement.
Which type of crack sealant is most appropriate for an active (moving) concrete crack?
Answer: Flexible polyurethane or polysulfide sealant
Flexible sealants accommodate cyclic movement in active cracks, while rigid materials would crack again under repeated opening and closing.