ATT Materials Finer Than No. 200 Sieve (Washing Test) 3

Question 1

An aggregate sample has an original dry mass of 2,012 g. After washing over the No. 200 sieve and oven drying, the retained mass is 1,966 g. What is the percent finer than No. 200?

Accepted Answer

2.3%

Answer

(2012 − 1966) / 2012 × 100 = 46/2012 × 100 ≈ 2.3%, so the percent finer than No. 200 is 2.3%.

Question 2

Why is it important that the No. 200 sieve used in ASTM C117 be inspected and cleaned before each test?

Accepted Answer

To prevent blinding from previous tests from reducing the effective opening size

Answer

Clay or fines from previous tests can blind (plug) the sieve openings, causing fines to be retained rather than passing, leading to an underestimate of percent finer.

Question 3

Which of the following best describes 'decanting' in the context of ASTM C117?

Accepted Answer

Pouring off the wash water carrying suspended fines over the nested sieves

Answer

Decanting means carefully pouring the turbid wash water (carrying suspended fines) over the No. 200 sieve while keeping the coarse aggregate in the container.

Question 4

Per ASTM C117, what must be done with any material retained on the No. 200 sieve after washing?

Accepted Answer

Returned to the main sample before oven drying

Answer

Material retained on the No. 200 sieve during washing must be returned to the main sample so that the total post-wash dry mass accurately represents all particles coarser than 75 µm.

Question 5

For a combined sieve analysis (ASTM C136 + ASTM C117), where should the material finer than No. 200 obtained by washing be entered in the gradation calculation?

Accepted Answer

It is added to the No. 200 pan mass from the dry sieve analysis

Answer

The washed fines are added to the pan (material finer than No. 200) from the dry sieve analysis to determine the total amount passing No. 200.

(ATT) ACI Aggregate Testing Technician Practice Test

(ATT) ACI Aggregate Testing Technician Practice Test

ATT Materials Finer Than No. 200 Sieve (Washing Test) 3