ACI Certification Strength Testing Technician 3

Question 1

What is the specified rate of load application when testing concrete cylinders for compressive strength per ASTM C39?

Accepted Answer

35 ± 7 psi/s (0.25 ± 0.05 MPa/s)

Answer

20 ± 5 psi/s (0.14 ± 0.03 MPa/s)

Answer

50 ± 10 psi/s (0.34 ± 0.07 MPa/s)

Answer

75 ± 15 psi/s (0.52 ± 0.10 MPa/s)

Question 2

Per ASTM C39, the bearing surfaces of cylinders must not depart from a plane by more than:

Accepted Answer

0.002 inch (0.050 mm)

Answer

0.001 inch (0.025 mm)

Answer

0.005 inch (0.13 mm)

Answer

0.010 inch (0.25 mm)

Question 3

Per ASTM C39, the diameter of a test cylinder used to calculate compressive strength must be the average of two measurements taken at:

Accepted Answer

Right angles to each other at or near mid-height

Answer

Both ends of the cylinder

Answer

The top and bottom third of the specimen

Answer

Any two convenient locations on the surface

Question 4

According to ASTM C39, what age tolerance is permitted when testing concrete cylinders specified for a 28-day strength result?

Accepted Answer

± 20 hours

Answer

± 4 hours

Answer

± 8 hours

Answer

± 12 hours

Question 5

A cylinder measures 5.90 inches long and 3.00 inches in diameter, giving an L/D ratio of approximately 1.97. Which statement best describes how to handle this specimen per ASTM C39?

Accepted Answer

Test and report the result with no correction since L/D is between 1.75 and 2.10

Answer

Discard it — L/D below 2.0 is not acceptable

Answer

Apply a correction factor because L/D falls below 1.94

Answer

Re-cure the specimen until it reaches full length

Question 6

Which fracture pattern described in ASTM C39 is characterized by a well-formed cone on one end with no significant cracking through the capping material?

Accepted Answer

Type 1 cone fracture

Answer

Columnar fracture

Answer

Diagonal shear fracture

Answer

Side fracture at top

Question 7

When a test result is the average of two companion cylinders and one shows damage due to an improper cap (not a concrete deficiency), what should be done per ASTM C39?

Accepted Answer

Discard the defective cylinder and report the companion result alone

Answer

Average both cylinders as normal and report the result

Answer

Report the defective cylinder at zero strength

Answer

Retest both cylinders after recapping