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
Carbonation of concrete is most likely to cause:
Answer: A reduction in pH that can lead to corrosion of reinforcement
Carbonation lowers concrete pH from ~12.5 to below 9, destroying the passive oxide layer that protects steel reinforcement.
When grinding concrete joints to restore load transfer in a slab, what is the primary goal?
Answer: Reducing differential vertical movement (faulting) between adjacent panels
Diamond grinding levels faulted joints to eliminate differential movement that causes rough riding surfaces and pavement damage.
Hydrostatic pressure on a below-grade concrete wall is best countered by a repair that:
Answer: Applies a hydraulic cement plug from the negative (dry) side
Hydraulic cement can be applied from the interior (negative) side to stop active water infiltration against hydrostatic pressure.
Spalling along the soffit of a concrete bridge deck is most commonly caused by:
Answer: Corrosion of reinforcing steel expanding and fracturing the cover concrete
Corrosion products occupy up to 6 times the volume of the original steel, creating expansive forces that spall the concrete cover.
Prior to applying a thin-bonded overlay, a pull-off (tensile bond) test on the prepared substrate should yield at least:
Answer: 200 psi
ACI 546 recommends a minimum substrate tensile strength of approximately 200 psi before placing bonded overlays.
What is the function of saw-cutting a repair area to a defined perimeter before removing deteriorated concrete?
Answer: It prevents feathered edges and creates a defined vertical face for bonding
Saw-cut perimeters create straight, vertical edges that prevent thin feathered patches which debond quickly.
Silane and siloxane penetrating sealers are applied to concrete surfaces primarily to:
Answer: Repel water and chloride ions by lining pore walls without forming a film
Silane/siloxane sealers penetrate the pore structure and chemically bond to create a hydrophobic lining, reducing water and chloride ingress.