NETTCP Concrete Testing 3

Question 1

What type of fracture pattern in a concrete cylinder indicates an unsatisfactory break and may require investigation?

Accepted Answer

Columnar fracture with no well-formed cone

Answer

A columnar fracture with no well-formed cone (Type 5 or 6 per ASTM C39) may indicate improper end conditions or capping problems.

Question 2

At what temperature range must concrete test specimens be initially cured after demolding per AASHTO T 23?

Accepted Answer

73°F ± 3°F (23°C ± 1.7°C)

Answer

AASHTO T 23 requires standard curing at 73°F ± 3°F (23°C ± 1.7°C) after demolding.

Question 3

When sampling concrete from a transit mixer, after how many revolutions at mixing speed must sampling begin per AASHTO R 60?

Accepted Answer

After 70 revolutions at mixing speed

Answer

Per AASHTO R 60, concrete must be mixed at least 70 revolutions at mixing speed before sampling.

Question 4

What is the purpose of the Kelly Ball test in fresh concrete testing?

Accepted Answer

Measure consistency as a field alternative to the slump test

Answer

The Kelly Ball test measures the penetration depth of a 30-lb ball to estimate consistency, serving as a quick field alternative to slump.

Question 5

How many individual samples must be composited to form one field sample for concrete testing per AASHTO R 60?

Accepted Answer

3 or more increments regularly spaced through the discharge

Answer

AASHTO R 60 requires compositing 3 or more individual samples taken at regularly spaced intervals throughout the middle portion of the load.

(NETTCP) New England Transportation Technician Certification Program Practice Test