NETTCP Concrete Testing 2

Question 1

According to AASHTO T 23, how long must freshly molded concrete cylinders remain undisturbed in their molds after casting?

Accepted Answer

16 to 32 hours

Answer

AASHTO T 23 requires cylinders to remain undisturbed in molds for 16 to 32 hours before initial curing.

Question 2

When performing the unit weight test on fresh concrete per AASHTO T 121, what is the correct procedure after filling the measure?

Accepted Answer

Strike off the top and weigh the measure

Answer

After filling and consolidating, the top surface must be struck off level before weighing the measure.

Question 3

Which condition would cause a concrete compressive strength test result to be considered invalid?

Accepted Answer

Cylinder end is not within 0.5 degrees of perpendicular

Answer

If cylinder ends are not within 0.5 degrees of perpendicular, the result may be unreliable and end preparation is required.

Question 4

What does the term 'w/cm ratio' refer to in concrete mix design?

Accepted Answer

Water to cementitious material ratio by weight

Answer

The w/cm ratio is the ratio of the mass of water to the mass of all cementitious materials in the mix.

Question 5

During the modified Proctor compaction test of soils under a concrete slab, how many layers are compacted?

Accepted Answer

5 layers

Answer

The modified Proctor test (AASHTO T 180) uses 5 layers compacted with 25 blows each.

(NETTCP) New England Transportation Technician Certification Program Practice Test