ACI Certification Field Testing Technician 3

Question 1

The aggregate correction factor (A) used in the pressure method air content test (ASTM C231) corrects for:

Accepted Answer

Air voids within aggregate particles that are not part of the paste air void system

Answer

The aggregate correction factor accounts for air absorbed within aggregate pores that the pressure meter would otherwise count as entrained air.

Question 2

The volumetric method (ASTM C173) is preferred over the pressure method (ASTM C231) when testing:

Accepted Answer

Lightweight aggregate concrete or concrete made with porous aggregate

Answer

The volumetric method is used for lightweight and porous aggregate concrete because the pressure method gives inaccurate readings due to aggregate porosity.

Question 3

When striking off excess concrete from the top of a unit weight measure per ASTM C138, the preferred instrument is:

Accepted Answer

A flat plate or piece of plate glass

Answer

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.

Question 4

Air content by the gravimetric method (ASTM C138) is calculated as:

Accepted Answer

(Theoretical unit weight minus Actual unit weight) divided by Theoretical unit weight times 100

Answer

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.

Question 5

Yield (volume of concrete produced per batch) per ASTM C138 is calculated as:

Accepted Answer

Total mass of all batch materials divided by unit weight of fresh concrete

Answer

Yield = total mass of all batch materials (lb or kg) divided by the unit weight of freshly mixed concrete.

ACI (American Concrete Institute Certification) Practice Test

ACI (American Concrete Institute Certification) Practice Test

ACI Certification Field Testing Technician 3