Aggregates are granular materials such as sand, gravel, crushed stone and recycled concrete used with cementing materials like cement or asphalt to produce concrete or asphalt. They make up 75% of concrete and over 90% of asphalt. Aggregates must be strong, durable and meet certain shape and size requirements. Common tests evaluate properties like strength, hardness, absorption and abrasion resistance. Sources of aggregates in Pakistan include limestone from Margalla Hills and Salt Range as well as dolomite deposits in Hazara and Kashmir regions.

1. Aggregates

2. Introduction:
 Aggregates are defined as inert, granular, and inorganic
material that normally consist of stone or stone like solids.
Aggregates are used :
In road bases as Asphalt Aggregates.
With ordinary Portland cement(OPC) as normal
aggregates as fills in foundations and as aggregate
accordingly to project specific studies.

3.  About three-fourth (75%) of the volume of Portland cement
concrete is occupied by aggregates. Other 25% include
cementing materials like cement, sand and synthetic
admixtures.
 Asphalt cement concrete occupy 90% or more of the total
volume. The remaining portion is mainly sand and Bitumen
which acts as cementing material in is Asphalt Aggregates.

4. Road Aggregate:
 By volume, aggregate generally account for 92 to 96% of
bituminous concrete.
 Road aggregate are the non-active inert material used to
provide mass to the base and sub-base courses.
 Road aggregate should have high strength to bear the traffic
load.
 Road aggregates must have higher impact value to withstand
the Tyre impact phenomenon.

5. Road aggregate mainly cubic angular which help in better
interlocking of the aggregate which in turn ultimately increases
the compressive strength.

6. Concrete Aggregate:
Portland cement concrete occupy volume of about 70-
80% of aggregates.
 Fine aggregates are used in making thin concrete slabs
where a smooth surface is required. Fine aggregate is
commonly known as Pan.
 Coarse aggregate is used for more massive members.

8. Uses of aggregates:
 We need aggregate to meet our basic needs of construction as under:
Civil Engineering
Structures
Public Sector
High Life Risk
Structures
Dams
Bridges
High Building
Towers
Low Life Risk
Structures
Roads
Schools
Hospitals
Private Sector
High Life Risk
Structures
Skyscrapers
Plazas
Monuments
Low Life Risk
Structures
Houses
Pavements
Safety Structures
(Parapets)
Sewerage storm
water drainage

9. Classification of Aggregates:
In Accordance with size:
 Course Aggregate:
Retained on the No.4 (4.75mm) sieve.
 Fine Aggregate:
Aggregate passing No.4 sieve and predominantly
retained on the No.200 sieve.

10. In Accordance with Source:
 Natural Aggregates: Aggregate is taken from natural
deposits. Some example are sand, crushed limestone,
dolomite and gravels.
 Manufactured Aggregates: Man-made materials
produces as a main product or an industrial by-product.
Some examples are blast furnace slag, lightweight
aggregate and heavy weight aggregate.

11. In Accordance with Weight:
Light weight aggregate:
Their unit weight is less than 1120kg/m3 and bulk density less
than 1800kg/m3. Examples are Cinder, blast furnace slag,
volcanic pumice.
 Normal weight aggregate: Their unit weight is 1520-
1680kg/m3 and bulk density of 2300-24—kg/m3.
 Heavy weight aggregate: Their unit weight is greater than
2100kg/m3 and the bulk density is greater than 3200kg/m3. A
typical example is magnetite limonite, a heavy iron ore.

12. Types of aggregates:
Granite aggregates
Granite aggregates are crushed hard rock of granular structure,
being the most common on Earth. It is the best aggregate for
high-grade concrete
 Gravel aggregates
Gravel aggregates are aggregates acquired as the result of
examining mined rock and by crushing natural stone rock. Gravel
aggregates are used for foundations and concretes

13.  Limestone aggregates
Limestone is one of the main types of aggregates that besides
the gravel and the granite types is used in road construction and
in production of reinforced concrete objects.
 Secondary aggregates:
 Secondary aggregate comes from crushing construction
waste – concrete, bricks, and asphalt. These aggregates
are used:
 As a large-scale filler for concretes
 In road construction as a filler for roads and ramps
 Slag aggregates
 Slag aggregates are obtained by crushing of smelter slag
 The cost of products from slag concretes is 20-30% lower
than traditional ones.

14. Properties of Aggregate:
 Strength
 Hardness
 Toughness
 Durability
 Shape of Aggregate
 Specific Gravity
 Absorption, Porosity, Permeability

15. Properties of Aggregate:
 Strength
• The aggregates should be sufficiently
strong to bear the subjected load due to
traffic wheel load, wear and tear,
crushing, and structure load.

16.  Hardness
• Hardness is the measure of resistance to crushing
and abrasion of aggregate.
• Aggregate are subjected to crushing and abrasive
wear during production, placing, compaction and
also subjected to abrasion under traffic load

17.  Toughness
• Toughness is the ability of aggregate to resist impact
forces
• Aggregates which lack adequate toughness and
abrasion resistance may cause construction and
performance problems.
 Durability
• Aggregates must be resistant to breakdown, and
disintegration from weathering or they may break
apart.
• Durability and soundness are terms typically given to

18.  Specific Gravity
• The ratio of the mass of unit volume of material at a
stated temperature to the mass of same volume of
gas -free distilled water at a stated temperature
• Higher value of specific gravity indicates better
aggregate, but the other properties should be
necessary.

19.  Absorption, Porosity, Permeability
• The size, number and continuity of pores
through the aggregate particles may affect
the strength of aggregate, abrasion
resistance, surface texture, specific gravity,
bonding capability and resistance to freeze
and thaw action.
• Aggregates with low specific gravity and
high water absorption are generally
considered unsuitable unless they have

20.  Shape of Aggregate
• Particle shape and surface texture are important for
proper compaction, deformation resistance and
workability.
• In Hard Mix Asphalt (HMA), since aggregates are
relied upon to provide stiffness and strength by
interlocking with one another, cubic angular-shaped
particles with a rough surface are best.

21. Tests on Aggregate:
Specific Gravity And Water Absorption Test:
Los Angeles Abrasion Test on coarse
aggregate:
Soundness Test:
Shape Test or Flakiness Index

22. Specific Gravity And Water
Absorption Test:
Apparatus:
 Oven
 Balance
 A wire mash basket not larger than
6.5mm
 A container in which basket may be
freely suspended.
 Two soft absorption cloths.

23. Procedure
 Sieving the sample through a No.4 sieve
 Wash the aggregate retained on No.4 sieve.
 Drying test sample.
 Immersion in the water.
 Placing the sample in wire mash basket and weigh in water
container at 23C.
 Using an absorbent cloth (towel) dry the surface of aggregate
by rolling up.
 Weigh the SSD (Saturated surface-dry condition) sample as
W2.
 Dry the sample in oven at 110C for 1-3hrs.cool in air at room
temperature, and then weigh as oven dry weight (W1).

24. Calculation:
Bulk specific gravity:
 Gsb= W2 /(W2 – W3)
W2 = SSD weight
W3 = Weigh in water
 Apparent Specific gravity:
Gsa = W1 /(W2– W3)
W1 = oven dry weight
 Absorption:
Abs% = [(W2 – W1) / W1] x 100

25. Important Points:
The specific gravity of normally used in road construction ranges
from 2.5 to 3.
High specific gravity of aggregate is indication of high strength.
Water absorption value ranges from 0.1% to 2% for aggregates
used in road surfacing.
Stone with absorption up to 4% have been used in base courses.
Generally, less than 0.6% is considered desirable for surface
course.

26. LOS ANGELES ABRASION TEST ON COARSE
AGGREGATE:

27. Apparatus:
 Los Angeles testing machine
 Test sieves
 Oven
 Balance
 12-steel balls of 46.0-47.6mm
in diameter
Sieve size Mass of indicated size(g)
Passing Retained Grading
A B C D
37.5mm 25.0mm 1250
25mm 19mm 1250
19mm 12.5mm 1250 2500
12.5mm 9.5mm 1250 2500
9.5mm 6.3 2500
6.3mm 4.74mm 2500
4.75mm 2.36mm 5000
Total 5000 5000 5000 5000

28. Principle:
 The Los Angeles test is a measure of degradation of mineral
aggregate
 Impact and grinding in a rotating steel drum containing a specified
number of steel balls.
 After the prescribed number of revolutions, and the aggregate
portion is sieved to measure the degradation as percentage loss.

29. Calculation:
Abrasion % = Wt. of initial sample – Wt. of retained of 1.7mm sieve x 100
Wt. of initial sample (total Wt.)
= Wt. of passing sieve (1.7mm) x 100
Wt. of initial sample
Important point:
 If it is less than 30% then this aggregate is suitable for all mixtures
 if it is more than 50% then this aggregate is unusual for any mixture

30. Soundness Test
Soundness is the resistance of aggregate to become worse by the
action of freeze and thaw.
Objective: the objective of test is to estimate the soundness of
aggregates subjected to weathering action.
Apparatus
 Test sieve
 Oven
 Balance
 Perforated Container for immersion of aggregate in solution
 Basket made of wire mesh

31. Main Principle:
 The soundness test is accomplished by repeated
immersion of test sample in saturated solution of
sodium sulfate followed by oven drying to partially or
completely dehydrate the salt precipitation in
permeable pore spaces.
 Repeat the process of immersion and drying until the
required no. of cycle is obtained.

32. Shape Test or Flakiness Index:
 Objective:
 This test is used to determine the percentage of
flakiness and elongation of particles in aggregate.
 The presence of flaky and elongated particles are
considered undesirable as they may cause
weakness or breaking down under load.

33.  Main Principle:
 The flakiness index of aggregate sample is found
by separating the flaky particles and expressing
their mass as a percentage of mass of Aggregate
sample.
 Apparatus:
 A thickness gauge
 Balance
 Metal trays
 Oven
 Sieves (flakiness measuring sieves) of size
related to the Thickness Gauge.

34. Problem Associated with Aggregates:
 Cleanliness and Deleterious Materials.
 Aggregates must be relatively clean.
 Vegetation, soft particles, clay lumps and excess dust matter
may affect performance by quickly degrading, which causes a
loss of structural support and/or prevents binder-aggregate
bonding.
 Clay
 The aggregate is carefully mixed with water in volumetric cylinder and
then let to settle.
 The clay particles will form layer with different color and structure on
the surface of aggregate.

35. Organic Impurities:
 Decaying vegetation may result in aggregates being contaminated
with organic matter.
 This material may have a retarding effect on the setting of
cementitious material and may result in lower strengths of the
hardened material at all ages.
 Organic impurities can be tested by colorimetric test. Tested
aggregate is mixed with sodium hydroxide (NaOH) or potassium
hydroxide (KOH) to prepare colored solution.
 The color of solution is compared with color of standard solution,
prepared according the standard. If the color of the test solution is
darker than the standard solution, than aggregate have to be
rejected.

36. Alkali-Reaction:
 One of the most important examples of reactive aggregates is
the Alkali-aggregate reaction in which alkali hydroxides react
with the reactive silicates to form alkali silica gels which
subsequently absorb water from their surroundings.
 This leads to internal stresses in hardened concrete until its
tensile strength is reached and it cracks.
 The method to control the alkali-aggregate reaction is to limit
the alkali content of the Portland cement to 0.6% or less.

37. BEST ROCK SOURCE AGGREGATE:
• The best rock source aggregate is a debatable topic depending upon
the project specific studies..
• Some materials used as aggregates have a higher specific gravity but
their impact values can be lesser as needed in the specific project
• . For example, the specific gravity of Limestone is 2.69 gm/cm3 and
of basalt is 2.91gm/cm3 but their impact values are 20 and 13
respectively which indicates that Limestone having lesser specific
gravity is more suitable in Asphalt aggregates whereas Basalts are
more suitable to be used in high life risk structures like columns and
foundations of bridges rather than to be used as Asphalt aggregate.
• However, the best aggregate sources with their workability are
Limestone, Dolerite, Basalts whereas Quartizites, Hornfels,
Microgranite are good but have less reserves.

38. SOURCE OF AGGREGATES IN PAKISTAN
• . Pakistan is country which is fully equipped with natural
resources. There are various aggregates sources in Pakistan meeting
the international engineering standards and comprise of compressive
strengths which can be used in any project.
• The most extensively used aggregate source in most of the
Pakistan is Margalla Hill Limestone, most of the quarrying activity is
observed in the margalla hill source located at Hassanabdal and
Taxila regions of Panjab.
• The sakesar limestone of Salt Range is also feeding most of the
southern Punjab and vicinity.
• There is a lot of construction material sources situated in Azad Jammu
and Kashmir. The Khwaja Seri area of Neelum valley has
considerable reserves of Dolerite.

39. • Khurshidabad Distt. Haveli has massive exposure of Limestone. Similarly,
the Bakot area near Kohala also of millions of tons of limestone.
• There is also a 10m thick bed of Margalla Hill Limestone in kamsar area
Yadgar section. The aforementioned sources are usable for strengths up to
3000 Psi and structures with greater life risk structures.
• There are unlimited resources of Dolomite in Abbottabad formation which is
exposed in most of Hazara, Muzaffarabad, Pir Panjal Range, District Kotli
(Karjai Antlicline) and other parts of Pakistan. The SS1 of Murree Formation
is a very considerable aggregate for marginal use if batch wise testing and
project specific studies area considered accordingly.