Construction Materials Testing & Quality Control Flashcards

What is the purpose of the 'ignition oven' method (AASHTO T 308) in HMA quality control?

Answer: Measure the asphalt binder content of a mix by burning off the binder

The ignition oven method burns the organic asphalt binder from the aggregate at high temperature, allowing calculation of binder content by weight difference.

During concrete paving operations, a KDOT inspector notices bleed water sheen on the surface during finishing operations. The correct action is to:

Answer: Delay finishing operations until the bleed water evaporates

Finishing concrete before bleed water evaporates traps water in the surface layer, creating a weak, porous layer prone to scaling and dusting.

A geosynthetic fabric is being placed as a separator layer between subgrade and aggregate base. What test property is most critical for this application?

Answer: Apparent opening size (AOS) and permittivity

For a separator application, the fabric must allow water drainage (permittivity) while retaining fine soil particles, making apparent opening size and permittivity the critical design properties.

When sampling freshly mixed concrete from a transit mixer per AASHTO T 141, composite samples must be collected over what minimum time span?

Answer: Between 10% and 90% of the load discharge

AASHTO T 141 requires composite samples to be collected from the middle portion of the load, between 10% and 90% of the total discharge, to avoid non-representative material.

A field moisture test on a soil sample using the speedy moisture tester (calcium carbide method) reads 8.2%. The true oven-dry moisture content is 7.9%. What does this indicate about the speedy tester result?

Answer: Both methods agree within acceptable tolerance for field use

A 0.3% difference between the speedy moisture tester and oven-dry method is within the acceptable tolerance for field quality control decisions.

What is the definition of 'lot' in KDOT's statistical acceptance plan for HMA pavement?

Answer: A defined quantity of material, typically 1,000–3,000 tons, used as the acceptance unit

A lot is a defined quantity of material (typically 1,000–3,000 tons) that serves as the unit for statistical acceptance testing and pay adjustment calculations.

During subgrade proof rolling with a loaded tandem-axle dump truck, which observation requires immediate corrective action?

Answer: Pumping or rutting greater than 1 inch with no rebound

Pumping, rutting greater than 1 inch, or lack of rebound indicates inadequate support or saturated conditions requiring subgrade stabilization or replacement before paving.