Field Testing Technician Flashcards
7 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 7 Field Testing Technician flashcards as text
The aggregate correction factor (A) used in the pressure method air content test (ASTM C231) corrects for:
Answer: Air voids within aggregate particles that are not part of the paste air void system
The aggregate correction factor accounts for air absorbed within aggregate pores that the pressure meter would otherwise count as entrained air.
The volumetric method (ASTM C173) is preferred over the pressure method (ASTM C231) when testing:
Answer: Lightweight aggregate concrete or concrete made with porous aggregate
The volumetric method is used for lightweight and porous aggregate concrete because the pressure method gives inaccurate readings due to aggregate porosity.
When striking off excess concrete from the top of a unit weight measure per ASTM C138, the preferred instrument is:
Answer: A flat plate or piece of plate glass
A flat plate or piece of plate glass is used in a sawing and rolling motion to create a smooth, level surface on the unit weight container.
Air content by the gravimetric method (ASTM C138) is calculated as:
Answer: (Theoretical unit weight minus Actual unit weight) divided by Theoretical unit weight times 100
Gravimetric air content = (D minus M) divided by D times 100, where D is the theoretical air-free unit weight and M is the measured unit weight.
Yield (volume of concrete produced per batch) per ASTM C138 is calculated as:
Answer: Total mass of all batch materials divided by unit weight of fresh concrete
Yield = total mass of all batch materials (lb or kg) divided by the unit weight of freshly mixed concrete.
Per ASTM C138, when the nominal maximum aggregate size exceeds 1.5 inches (37.5 mm), consolidation of the unit weight sample must use:
Answer: Internal vibration
ASTM C138 requires the vibration method when nominal maximum aggregate size exceeds 1.5 inches because hand rodding cannot adequately consolidate such mixes.
To calculate theoretical (air-free) unit weight for the gravimetric air content method, a technician needs:
Answer: Specific gravities and batch masses of all materials in the mix
Theoretical unit weight requires the specific gravity and batch mass of every ingredient (cement, aggregates, water, admixtures) to calculate.