ATT Sampling Aggregates 3

Question 1

When sampling coarse aggregate from a stationary truck, what depth below the surface should increments be obtained?

Accepted Answer

At least 300 mm (12 in.) below the surface

Answer

ASTM D75 requires digging at least 300 mm below the surface to avoid the biased, segregated layer at the top of the load.

Question 2

Which of the following is the most reliable method for obtaining a representative sample of fine aggregate from a stockpile?

Accepted Answer

Sampling from the flowing stream as material is loaded from the pile

Answer

Sampling from the moving stream during loading captures material from throughout the stockpile and avoids surface segregation bias.

Question 3

The term 'field sample' in ASTM D75 refers to:

Accepted Answer

The sample collected at the source before any reduction

Answer

The field sample is the total quantity of aggregate collected on-site from the source before it is reduced to individual test specimens.

Question 4

Which condition makes it necessary to increase the number of increments when sampling from a conveyor belt?

Accepted Answer

When the material shows high variability or segregation

Answer

Higher material variability requires more increments to achieve a composite sample that adequately represents the aggregate being sampled.

Question 5

Aggregate sampling plans should be developed with input from which parties?

Accepted Answer

All parties involved in the project including purchaser, producer, and testing laboratory

Answer

ASTM D75 recommends that sampling plans be developed cooperatively among all stakeholders to ensure the plan meets project acceptance requirements.

(ATT) ACI Aggregate Testing Technician Practice Test