Curing, Protection & Quality Control 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 Curing, Protection & Quality Control flashcards as text
Which defect is characterized by a thin, weak layer separating from the surface of a hardened concrete slab?
Answer: Delamination
Delamination is the separation of a thin surface layer caused by bleed water and air trapped beneath a prematurely sealed surface.
When sampling fresh concrete for quality control testing, ASTM C172 requires the composite sample to be obtained over what time period?
Answer: No more than 15 minutes
ASTM C172 requires that the composite sample be collected over a period of no more than 15 minutes to represent a single batch or load.
What is the primary cause of efflorescence on concrete surfaces?
Answer: Soluble salts carried to the surface by migrating water
Efflorescence forms when water moves through concrete, dissolves soluble salts, and deposits them on the surface as white crystalline deposits upon evaporation.
According to ACI quality control requirements, how many standard 6×12-inch cylinders should be made per strength test when testing for acceptance?
Answer: Two cylinders per test
ACI 318 requires a minimum of two cylinders per strength test, with results averaged for acceptance evaluation.
Concrete scaling in cold climates is most effectively prevented by:
Answer: Ensuring adequate air entrainment (4–7%) and proper curing
Adequate air entrainment provides freeze-thaw resistance, and proper curing achieves the strength and density needed to resist scaling.
A concrete finisher notices bleed water is still visible on the surface. The correct action is to:
Answer: Wait until the bleed water has evaporated or been reabsorbed before finishing
Finishing over bleed water incorporates excess water into the surface, increasing the w/c ratio and causing weakness, scaling, and crazing.
What does the term 'protected curing period' refer to in cold weather concreting per ACI 306?
Answer: The time concrete must be kept above 50°F (10°C) to achieve adequate strength before exposure to freezing
ACI 306 defines the protected curing period as the time concrete must be maintained above 50°F to develop sufficient strength to resist freezing damage.