Aggregates

Question 1

How much % does the agg. represents in concrete volume?

Answer 1

60%-75%

Question 2

How much % does the agg represents in concrete mass?

Answer 2

70%-85%

Question 3

Why do we use agg. in concrete?

Answer 3

• Economical benefits
• Volume stability

Question 4

What are the 2 size of aggregates?

Answer 4

Fine and coarse

Question 5

What are the fine agg.?

Answer 5

Sand and/or crushed stones

Question 6

What are the coarse agg.?

Answer 6

Gravel and crushed stone

Question 7

What are the typical size of fine agg. in mm?

Answer 7

<5mm (>5mm for coarse agg.)

Question 8

What are the 4 types of weight of agg.?

Answer 8

1. normal weight
2. light weight
3. structural light weight
4. Heavy weight

Question 9

What is the density of light weight?

Answer 9

250 to 1450 kg/m3

Question 10

What is the density of normal weight?

Answer 10

2200 to 2400 kg/m3

Question 11

What is the density of stru. light weight?

Answer 11

1450 to 1850 kg/m3

Question 12

What is the density of heavy weight?

Answer 12

up to 6400 kg/m3 (high density)

Question 13

What are the 4 sources of agg.?

Answer 13

Natural gravel and sand
Rocks and minerals
Crushed blast-furnace slag
Recycled waste concrete

Question 14

How can we determine the distribution of agg. (grading)?

Answer 14

Sieve analysis with mesh sieve

Question 15

What are the 7 sieves for fine agg.?

Answer 15

9.5mm
4.75mm
2.36mm
1.18mm
600 micromm
300 micromm
150 micromm
(pan)

Question 16

What are the 13 sieves for coarse agg.?

Answer 16

100mm
90 mm
75 mm
63mm
50 mm
37.5 mm
25 mm
19 mm
12.5 mm
9.5 mm
4.75 mm
2.36 mm
1.18 mm
(pan)

Question 17

What is the purpose of distribution curve?

Answer 17

To see if the grading of agg is good or bad

Question 18

What is max size of agg. (SIEVE)?

Answer 18

smallest sieve that all the agg. passes throught.

Question 19

What is the nominal maximum size?

Answer 19

Standard sieve opening immediately after the max. size of agg.?
Note: must not exceed–> 1/5 of narrowest dimension between sides of forms, 3/4 of clear spacing between rebars and between rebars and the form and 1/3 depth slabs

Question 20

What is FM?

Answer 20

Sum of the cumulative percentages by mass of a sample of agg. retained in each of standard sieves and dividing the sum by 100. (EXCLUDING PAN)

Question 21

What is the FM of Coarse agg.?

Answer 21

2.8-3.1

Question 22

What is the FM of fine agg.?

Answer 22

2.3-2.5

Question 23

What are the ideal moisture conditions for fine and coarse aggregates?

Answer 23

Saturated surface dry (SSD)

Question 24

Larger coarser agg. =?

Answer 24

lower S.A. –> Lower cement and water required –> less workability and more strength (less w/c ration)

Question 25

What is D-Cracking?

Answer 25

Cracking of concrete caused by freeze-thaw deterioration of the agg. within concrete.

Question 26

What is ASR? (alkali silica reaction)

Answer 26

Alkali hydroxide + Reactive silica = Alkali silica gel
Alkali silica gel + moisture (H2O) = EXPANSION

Question 27

How to control ASR?

Answer 27

Non -reactive agg.
Limit alkali loading
Lithium based admx.
SCM’s (fly ash; slag; silica fume)
Limestone sweetening

Question 28

How does the agg. should be stored?

Answer 28

avoid contamination
avoid segregation