ATT Unit Weight & Voids Testing 3

Question 1

In the unit weight test, why is it important to avoid vibrating the measure during filling?

Accepted Answer

Vibration increases packing beyond the standard procedure, giving artificially high results

Answer

External vibration compacts aggregate beyond what the standard procedure intends, producing a unit weight higher than the standardized result.

Question 2

What is the minimum size of measure required for aggregate with a nominal maximum size of 1.5 inches per ASTM C29?

Accepted Answer

1 cubic foot

Answer

ASTM C29 requires a 1-cubic-foot measure when the aggregate nominal maximum size is 1.5 inches.

Question 3

Which of the following conditions would cause the measured unit weight of coarse aggregate to be lower than the true value?

Accepted Answer

Having a dented or deformed measure that increases its volume

Answer

A deformed measure with a larger-than-calibrated volume holds more aggregate, making the calculated unit weight (mass/volume) artificially low.

Question 4

The voids-in-aggregate formula uses the term 'W' to represent what quantity?

Accepted Answer

Bulk unit weight of the aggregate

Answer

In ASTM C29, W is the bulk unit weight (unit weight) of the aggregate determined by the standard test.

Question 5

According to ASTM C29, what is the standard number of drops of the measure against the base when using the jigging compaction method?

Accepted Answer

50 drops per layer

Answer

The jigging method requires the measure to be raised and dropped 50 times per layer as specified in ASTM C29.

(ATT) ACI Aggregate Testing Technician Practice Test