1. Aggregates

2. Fine aggregate Coarse aggregate Less than 4.75 mm
Greater than 4.75 mm (maximum 80mm)

3. Source Natural aggregate Artificial aggregate Sand
Crushed rock such as Quartzite, Basalt, Sandstone
Broken brick
Sintered fly ash

4. Test on Aggregates Crushing strength Impact strength Flakiness index
Elongation index
Abrasion resistance

5. Crushing strength

6. Crushing strength Crushing value = 𝑊1 𝑊2 x 100%
W1 = Weight of fraction passing 2.36mm IS Sieve
W2 = Weight of dry sample

7. Impact strength

8. Impact strength Impact value = 𝑊1 𝑊2 x 100%
W1 = Weight of fraction passing 2.36mm IS Sieve
W2 = Weight of dry sample

10. Flakiness index
The flakiness index of aggregate is the percentage by weight of particles in it whose least dimension (thickness) is less than 3/5th (0.6) of their mean dimension

11. Thickness and length gauges

12. Thickness gauge

13. Flakiness index = 𝑀1 𝑀2 x 100%
M1 = mass of materials passed through slots
M2 = initial mass of materials taken
Flakiness of aggregates for construction should be less than 15%

14. Elongation index
Elongation index of an aggregate is the percentage by weight of the particles whose greater dimension is greater than th (1.8 times) of their mean dimensions

15. Length gauge

16. Elongation index = 𝑀1 𝑀2 x 100%
M1 = mass of materials retained through gauge
M2 = initial mass of materials taken
Presence of elongated particles in excess of 15% is undesirable

17. Abrasion Resistance test
Resistance to wear
Aggregates used for road and pavement construction should have sufficient resistance to withstand the wear and tear.

18. Deval Abrasion test
Dorry Abrsion test
Los angeles abrasion test

19. Grading of aggregate
Grading of aggregate means particle size distribution of the aggregate
Principle of grading is that the smaller size particles fill up the voids left in larger size particles
Aggregate size
80mm, 40mm, 20mm, 10mm, 4.75mm, 2.36mm, 1.18mm, 600μ, 300μ, 150μ

20. Well graded aggregate
Well graded aggregate produces dense concrete and needs smaller quantities of fine aggregate and cement
Highly workable

21. Bulking of sand
Presence of moisture content increases the volume of sand.
This phenomena is known as “bulking of sand”

22. Alkali aggregate Reaction
Some of the aggregates contains reactive silica, which reacts with alkalies (Na2O, K2O) present in cement

23. Factors Promoting Alkali aggregate Reaction
Reactive type aggregate
High alkali content in cement
Availability of moisture