ACI Certification Strength Testing Technician 5

Question 1

A concrete cylinder intended for compressive strength testing was inadvertently allowed to surface-dry before testing. What must be done per ASTM C39?

Accepted Answer

Re-wet the specimen and allow it to re-soak before testing

Answer

Test immediately and note the dry condition on the report

Answer

Discard the specimen and recast new cylinders

Answer

Apply a moisture correction factor to the measured strength

Question 2

Which piece of information is NOT typically required on a concrete cylinder identification tag used in the field?

Accepted Answer

Exact mix design proportions by weight

Answer

Date and time of casting

Answer

Truck or load identification number

Answer

Location or structural element where concrete was placed

Question 3

Per ASTM C31, after the initial curing period, standard-cured specimens must be stored in water or a moist room at what specified nominal temperature?

Accepted Answer

73°F (23°C)

Answer

60°F (16°C)

Answer

68°F (20°C)

Answer

80°F (27°C)

Question 4

What is the primary purpose of making both field-cured and standard-cured cylinders from the same concrete placement?

Accepted Answer

To evaluate the adequacy of curing and protection applied in the field

Answer

To verify that the concrete mix design meets specified proportions

Answer

To confirm the testing machine is properly calibrated

Answer

To establish acceptance test results for specification compliance

Question 5

Per ASTM C617, how long must a sulfur mortar cap be allowed to harden before the capped cylinder can be tested?

Accepted Answer

2 hours

Answer

30 minutes

Answer

1 hour

Answer

6 hours

Question 6

When a single 28-day compressive strength test result falls below the specified f'c, what is the first step per ACI 318 acceptance criteria?

Accepted Answer

Determine whether the result is more than 500 psi below f'c and whether overall acceptance criteria are still met

Answer

Immediately require removal of the concrete represented by the failing test

Answer

Stop all concrete placement until additional cylinder tests are completed

Answer

Require the contractor to perform core testing on the structure immediately

Question 7

A technician measures a cylinder's diameter twice at mid-height and gets 5.96 inches and 6.00 inches. To what precision and value should the diameter be recorded for the strength calculation?

Accepted Answer

5.98 inches (nearest 0.01 inch)

Answer

6.0 inches (nearest 0.1 inch)

Answer

6.00 inches (rounded to nominal)

Answer

5.96 inches (smaller of the two)