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1. Materials for Concrete
Aggregates(Combined)

2. Materials for Concrete
• Occupy 70-75% of the total volume of
concrete
• Defined as an inert mineral filler for OPC –
BIS, ASTM, ACI & BS 882 codes

3. Aggregates(Combined)
Aggregates are the inert filler materials,
such as sand or stone, used in making
concrete

4. Aggregates
• Coarse Aggregates (4.75mm-80mm)
Broken Stones & Gravels
• Fine Aggregates (<4.75mm)
Gravel, Sand, Silt & Clay

5. Fine & Coarse Aggregates
• Fine Aggregate - <4.75mm (5mm)
• Coarse Aggregate - >4.75mm & up to 80mm
• Boulders – Beyond 80mm
• Grading:
Fine Aggregate Coarse Aggregate
C-Coarse 40, 20, 14mm down
M-Medium till 4.75 mm
F-Fine

6. Sizes
• Coarse aggregate e.g.
Gravel – 4.75mm or
more (5mm)
• Fine aggregate e.g.
sand – less than
4.75mm
• Silt – varies from
0.02mm – 0.06mm
• Clay – much finer than
0.02mm

7. Classification
• A) Petrological – BS 812
• B) Density
• C) Shape & texture

8. A) Petrological
1.) Igneous rocks - Granites, basalts
dolerites, gabbro & porphyries – Hard, tough,
dense – Excellent aggregates
2.) Sedimentary rocks - Sandstones -
When hard & dense suitable - Siliceous
better than calcareous which are liable to acid
attack
Limes Stones - Sedimentary rocks chiefly
composed of calcium carbonate Harder, denser
types are suitable

9. A) Petrological
Shale - Poor aggregates – weak, soft, laminated
& absorptive
3.) Metamorphic rocks - Variable characters
– marbles & quartzite usually massive, dense &
adequately tough & strong
Schist & slates are often thinly laminated &
therefore unsuitable

10. B) Density
1.) Heavy – SG>4.0
i) Magnetic, natural iron ore (Fe3O4)
ii) Barytes (BaSO4)
2.) Normal SG 2.5-3.0
i) Sands & gravels – division is arbitrarily on size – sands
pass 4.76 mm BS sieve
ii) Granites & basalts – hard & tough
iii) Sandstone – hard & dense types
iv) Limestone – hard & dense types
v) Broken bricks – must be free of plaster – low sulphur
content
vi) Air cooled blast furnace slag

11. B) Density
3.) Lightweight - SG<2.5
i) Sintered PFA
ii) Foamed slag
iii) Vermiculite
iv) Expanded polystyrene
v) Pumice
vi) Wood waste

12. C) Shape & Texture
• Particle shape classified to BS 812 : 1975
• Terms used:
• Well rounded, rounded, sub-rounded, sub-angular,
angular

13. • Surface texture classified to BS 812 : 1975
• Relates to the degree of polish or dullness, smoothness
or roughness of particles surfaces
• Depends on hardness, grain size and pore character
• Note: BS 812 & BS 882 have been
replaced by BS EN 12620
C) Shape & Texture

14. Bond of Aggregate
• Partly due to interlocking
• Partly due to physical & chemical
characteristics of the aggregate
• Other factors include the cement paste

15. Aggregate Properties
• Ideally should be chemically inert, durable,
hard & tough
• Should be capable of being compacted to
the appropriate density & provide good
bonding with the cement paste

16. A) Chemical Properties
• Soluble salts – sulphates - cause problems
with hydrated cement or chloride which
accelerate hydration & increase risk of
corrosion of steel reinforcement.
• Reactive aggregates of lime stone or rock
based vulnerable to Alkalies in the cement
resulting with formation of AAR (Alkaline
Aggregate Reaction) – an expansive
compound or ASR (Alkaline Silica Reaction) –
‘concrete cancer’ – not common now but has
been a problem in the past.

17. Alkali-Silica Reaction

18. • Clay & silt – defined as materials passing
a 75 micron sieve – harmful to concrete in
substantial amounts – increase specific
surface & hence water requirements
• Weak (unsound particles) – lower the
strength of the concrete
Other Harmful Substances

19. B) Physical Properties
• Strength
• Porosity
• Thermal
• Bonding
• Moisture
• Density - relative (SSD) & solid (x1000)
- bulk (packing air)

20. Relative Density - Calculation
• Relative Density or Specific Gravity(SSD)
=
Mass of sample of SSD aggregate
Volume of water displaced SSD sample x 1000
Where, SSD = saturated surface dry – all
accessible pores are full of water, but the
aggregate surface is dry

21. Bulk Density(Unit Weight)
• Stockpiles of loosely packed aggregates contain
large volumes of air trapped between particles,
usually many times that of the volume of air
present within the particles – ‘Bulking’
• Coarse aggregates – 30-50% of total space
occupied
• Fine aggregate – approx 20% - varies with
moisture content

22. Batching of Aggregates
• Bulking of aggregates
produce uncertainty in
the solid content of
aggregates batched by
volume
• Batching by weight
(mass) is therefore
preferred, hence most
concrete mixes are
batched by weight

23. Grading of Aggregates
• Refers to the size & distribution of the aggregate
• Sieve analysis – BS 410 : 1976
• Grading limits – BS 882 : 1983
Note: The Euro-standard BS EN 12620
now covers testing & specification for
aggregates

24. Graded Aggregate
• Uniform Graded – equal weights of each
particle size present
• Gap graded – several consecutive particle
sizes missing
• Single graded – consist predominantly of a
single particle size

25. Aggregate Durability
• Soundness – degradation through
interstitial crystallisation
• Organic matter – act as retarders
• Mica – Muscovite or Biotite
• Chalk – affects strength (freeze/thaw)
• Shell – strength

26. • Sulphates – limited to 4% overall
• Chlorides – corrosion (<0.06%)
• Metallic Pyrites – Lead, Zinc, Iron
impurities
Aggregate Durability

27. Coarse Aggregates (Broken Stones)
Procurement process:
Quarrying of Stone
1. Excavating
2. Heating
3. Wedging
4. Blasting

28. Coarse Aggregates (Broken Stones)
Characteristics of Coarse Aggregate based on
1. Appearance
2. Strength
3. Hardness, Toughness and Resistance to Abrasion
4. Durable
5. Porosity and Absorption
6. Workability

29. Profile of different stones
S.
No
Name of
Stone
Characteristics Uses Places of
Occurrence
1 Granite Un-stratified and has crystalline
granular structure – Very Heavy
and Hard.
Used in the construction of
bridges marine works etc.
Widely throughout
in INDIA
2 Gneiss Stratified – can be split into thin
slabs
Used for paving the floors
and roads
Tamil nadu, Kerala
Karnataka,AP, Bihar
4 Slate Can be split into thin sheets –
found in variety of colors
Used for roof covering,
flooring, sills of doors and
windows
AP, MP, Punjab
5 Sandstone Found in variety of colors Used for jali work, ashlar
work and carving work.
Trichy, mysore,
Karnool
6 Marble Crystalline and compact – found
in variety of colors – dressing and
carving can be easily done.
Used to beautify buildings Kadappa, Kurnool,
Rajasthan,
7 Limestone Consists of mainly CaCO3 Used for the manufacturing
of lime and cement. Used in
building construction.
Tamil Nadu, AP,
Maharashtra
8 Quartzite Compact, hard and brittle – strong
and durable
Used as road metal, railway
ballast, concrete aggregate
Coimbatore, Salem,
Karnataka

30. Fine Aggregates
Size: (<4.75mm)
Types of Fine Aggregates
1. Gravel
2. Sand
3. Silt
4. Clay

31. Sand & Gravel
• Sources – pits or dredging from river or sea bed –
screening & washing
• Marine aggregates
Problems with Marine Aggregates
• Liable to contain impurities of shell & salt
• Granites, sandstones or lime stones – generally
unconsolidated sedimentary deposits
• 50% of aggregates came from sand & gravel
deposits
• Emphasis has now shifted to hard rock sources

32. Fine Aggregates - Sand (<4.75mm)
Important Properties
1. Permeability
2. Consolidation
3. Shear Strength

33. Aggregate Uses
• Concrete
• Mortar
• Renders
• Screeds
• Unbound pavements

34. • Bituminous
Materials
• Railway ballast
• Filter media -
biological
Aggregate Uses