ATT Bulk Density, Voids & Organic Impurities 4

Question 1

What value of water density is used in the ASTM C29 void content calculation?

Accepted Answer

62.3 lb/ft³ (998 kg/m³)

Answer

ASTM C29 uses 62.3 lb/ft³ (997.5 kg/m³) as the standard density of water for computing void content.

Question 2

A coarse aggregate has a bulk density of 1680 kg/m³ and a bulk specific gravity of 2.65. What is its approximate void content? (Water density = 1000 kg/m³)

Accepted Answer

36.6%

Answer

Void content = (2.65 × 1000 − 1680) / (2.65 × 1000) × 100 = 970 / 2650 × 100 ≈ 36.6%.

Question 3

If an aggregate fails the ASTM C40 color test, what is the recommended next step per the standard?

Accepted Answer

Perform a mortar strength test per ASTM C87

Answer

A failing color result does not automatically disqualify the aggregate; ASTM C87 mortar strength testing can determine whether organic material actually harms concrete performance.

Question 4

After rodding each layer in the ASTM C29 bulk density test, how should the aggregate surface be prepared before adding the next layer?

Accepted Answer

Leveled by rolling the tamping rod across the surface

Answer

After rodding each layer, ASTM C29 requires leveling the aggregate surface by rolling the tamping rod across it before adding the next layer.

Question 5

What length is specified for the tamping rod used in ASTM C29 bulk density testing?

Accepted Answer

600 mm (24 in)

Answer

ASTM C29 specifies the tamping rod to be approximately 600 mm (24 in) in length with a hemispherical working end.

(ATT) ACI Aggregate Testing Technician Practice Test

(ATT) ACI Aggregate Testing Technician Practice Test

ATT Bulk Density, Voids & Organic Impurities 4