Question

Laboratory specific gravity and absorption tests are run on two coarse aggregate sizes, which have to blended.

The results are as follows:

Aggregate A: Bulk specific gravity 2.491; absorption 0.8%
Aggregate B: Bulk specific gravity 2.773. absorption 4.6%

a. What is the specific gravity of a mixture of 50% aggregate A and 50% aggregate B by weight?

b. What is the absorption of the mixture?

c. What should be the proportion of aggregate A in the blend, so that the mixture will have a bulk specific gravity of 2.650?

d. What should be the proportion of aggregate A in the blend, so that the mixture will have an absorption capacity of 4%?

Answer 1

a) Specific Gravity G = 2.624

b) Absorption of the mixture = 2.7%

Step-by-step explanation:

Given that:

Bulk specific gravity of aggregate A is G₁ = 2.491

Bulk specific gravity of aggregate B is G₂ = 2.773

Absorption percentage of aggregate A = 0.8%

Absorption percentage of aggregate B = 4.6%

Answer 2

A. the specific gravity of mixture= 2.624

B. absorption of the blend is 2.7%

Step-by-step explanation:

Given that Bulk specific gravity of Aggregate A= 2.491

Given that Bulk specific gravity of Aggregate B G2=2.773

Absorption percentage of Aggregate A= 0.8%

Absorption % of Aggregate B= 4.6%

Decimal fraction of weight of Aggregate A P1=50%

Decimal fraction by weight of Aggregate B P2= 50%

The aggregate given are blended in 50% weight.

A. Composite gravity = 1/(P1/G1 + P2/G2)

Which is

1/(0.5/2.491 + 0.5/2.773)

=1/0.381

=2.624

Therefore, the specific gravity of mixture= 2.624

B. Absorption of blended aggregate is the simple weighted sum of the absorption of components.

Mathematically, it is expressed a X= P1X1 + P2X2

Where,

X1= absorption of Aggregate A

X2=absorption of Aggregate B

Absorption of blended aggregate is

(0.5x0.8) + (0.5×0.46)

= 2.7%

Therefore absorption of the blend is 2.7%