Concrete Construction Inspection Flashcards
6 cards from real ACI Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Concrete Construction Inspection flashcards as text
During concrete placement, what is the maximum free-fall height typically permitted for concrete without causing segregation?
Answer: 5 feet (1.5 m)
ACI 301 and general practice limit free-fall of concrete to about 5 feet (1.5 m) to prevent aggregate segregation; exceeding this can cause mortar and coarse aggregate to separate.
What is the primary purpose of consolidating concrete using internal vibration during placement?
Answer: To remove entrapped air and ensure the concrete completely fills the form without voids
Internal vibration consolidates fresh concrete by reducing entrapped air voids and ensuring the concrete flows around reinforcement and form edges, resulting in denser, stronger hardened concrete.
When inspecting reinforcing bar placement, the ACI concrete construction special inspector checks that cover to reinforcement meets the specified minimum. What is the typical minimum clear cover for cast-in-place concrete exposed to weather (bars #6 and larger)?
Answer: 2 inches (50 mm)
ACI 318 Table 20.6.1.3.1 requires 2 inches (50 mm) of clear cover for #6 and larger bars in cast-in-place concrete exposed to weather.
An inspector observes that the concrete delivered to the site has a slump 3 inches higher than specified. What is the correct course of action?
Answer: Reject the load and notify the contractor and engineer of record before placement
A load that exceeds the specified slump tolerance must be rejected; only the engineer of record can authorize using out-of-spec concrete, and field additions of dry cement are not permitted.
What does 'honeycombing' in hardened concrete indicate, and what is its primary cause?
Answer: Voids in the concrete matrix caused by inadequate consolidation or segregation, leaving coarse aggregate exposed
Honeycombing refers to voids or open texture in hardened concrete where mortar failed to fill spaces between coarse aggregate particles, typically due to inadequate vibration, over-stiff mixes, or reinforcement congestion.
According to ACI 305R, what is the maximum concrete temperature at point of discharge permitted without special hot-weather precautions?
Answer: 95°F (35°C)
ACI 305R recommends that concrete temperature at point of discharge not exceed 95°F (35°C); higher temperatures accelerate hydration, reduce workability, and can lead to strength loss.