ACI Certification Concrete Construction Inspection 2

Question 1

During concrete placement, what is the maximum free-fall height typically permitted for concrete without causing segregation?

Accepted Answer

5 feet (1.5 m)

Answer

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.

Question 2

What is the primary purpose of consolidating concrete using internal vibration during placement?

Accepted Answer

To remove entrapped air and ensure the concrete completely fills the form without voids

Answer

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.

Question 3

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)?

Accepted Answer

2 inches (50 mm)

Answer

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.

Question 4

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?

Accepted Answer

Reject the load and notify the contractor and engineer of record before placement

Answer

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.

Question 5

What does 'honeycombing' in hardened concrete indicate, and what is its primary cause?

Accepted Answer

Voids in the concrete matrix caused by inadequate consolidation or segregation, leaving coarse aggregate exposed

Answer

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.

ACI (American Concrete Institute Certification) Practice Test

ACI (American Concrete Institute Certification) Practice Test

ACI Certification Concrete Construction Inspection 2