Concrete Field Inspector Flashcards

What is the purpose of striking off (screeding) concrete immediately after placement?

Answer: To level the concrete to the desired grade or form elevation

Screeding removes excess concrete and brings the surface to the required grade or elevation defined by the forms or screeds.

According to ACI 305, what maximum concrete temperature at point of delivery is typically recommended for hot weather concreting?

Answer: 90°F (32°C)

ACI 305 recommends that fresh concrete temperature at delivery should not exceed 90°F (32°C) to minimize adverse hot weather effects.

A concrete cylinder that is tested at 27 days instead of 28 days will typically show:

Answer: Slightly lower strength, acceptable if within specifications

Concrete gains strength slightly day by day, so a 27-day result is marginally lower than 28-day, but many specs allow a ±1 day tolerance.

What does a 'cold joint' in concrete indicate?

Answer: A plane of weakness formed when fresh concrete is placed against hardened concrete

A cold joint forms when fresh concrete is placed against a layer that has already set, resulting in a weak bond plane.

Which of the following actions is NOT appropriate when concrete fails the slump test on arrival?

Answer: Allow the contractor to add water up to the maximum w/c ratio

Water should never be added to a delivered load in the field to adjust slump without written authorization and without exceeding the design w/c ratio.

What is the purpose of a curing compound applied to a concrete surface?

Answer: To retain moisture in the concrete to promote hydration

Curing compounds form a membrane that retains moisture needed for continued cement hydration, achieving design strength.

When rodding a 4-inch diameter concrete cylinder, how many layers and rod strokes per layer are required per ASTM C31?

Answer: 3 layers, 25 strokes each

ASTM C31 requires 4-inch diameter cylinders to be filled in 3 equal layers and rodded 25 times per layer.