The presentation covers a detail on the aggregates used in concrete (like Coarse aggregate & Fine Aggregate), fine aggregates, coarse aggregate properties, coarse aggregate, size, coarse aggregate definition, difference between coarse and fine aggregate, fine aggregate size, fine aggregate size, Properties of fine aggregate etc. Provided by www.happho.com www.happho.com is a One Stop Solution for House Construction, Interiors & Renovation and is an Online Marketplace for Construction Materials in India

1. FUNCTIONS AND IMPORTANCE OF
AGGREGATE IN CONCRETE
APPLICATIONS
Vinod Kumar Singh
Co-founder, www.Happho.com
www.happho.com is an Online Marketplace for Construction Material & One Stop
Solution for Bungalow Construction & Interiors

2. CONCRETE
Basic Definition:
Concrete is a composite material that essentially consists of a binding medium embedded with
Fine-Aggregate (typically sand) and Coarse Aggregate (typically gravel) with or without
chemical and mineral admixture and filler.
• Constituents:
Mixture of aggregate and paste
• Cement paste - 30 to 40%
– Portland cement + Mineral Admixture 7% to 15% by Vol.
– Water + Chemical Admixture 14% to 21% by Vol.
• Aggregates - 60% to 70%
– coarse aggregates
– Fine aggregates

3. Typical Concrete Proportion by Volume:
CONCRETE

4. AGGREGATE
• Aggregate is relatively inexpensive and does not enter into complex chemical reactions
with water; it has been customary, therefore, to treat it as an inert filler in concrete.
• However, due to increasing awareness of the role played by aggregates in determining
many important properties of concrete, the traditional view of the aggregate as an inert filler
is being seriously questioned.
• It is true that aggregate strength is usually not a factor in normal concrete strength
because, with the exception of lightweight aggregates, the aggregate particle is several
times stronger than the matrix and the interfacial transition zone in concrete. In other
words, with most natural aggregates the strength of the aggregate is hardly utilized
because the failure is determined by the other two phases.
• There are, however, aggregate characteristics other than strength, such as the size,
shape, surface texture, grading (particle size distribution), and mineralogy which are known
to affect concrete strength in varying degrees.

5. BASIC FUNCTIONS OF AGGREGATE
• Cheap fillers
• Hard material
• Provide for volume stability
• Reduce volume changes
• Provide abrasion resistance
It is inappropriate to treat the aggregate with any less respect than cement.

6. NOMENCLATURE & CLASSIFICATION
Aggregates are generally classified according to particle size, bulk density, or source sieve).
• Coarse aggregate is used to describe particles larger than 4.75 mm, and the term fine
aggregate is used for particles smaller than 4.75mm; typically, fine aggregates contain
particles in the size range 75 µm to 4.75 mm, and coarse aggregates from 4.75 to about 50
mm, except for mass concrete which may contain particles up to 150 mm.
• Most natural mineral aggregates, such as sand and gravel, have a bulk density of 1520 to 1680
kg/m3
and produce normal-weight concrete with approximately 2400 kg/m3
unit weight.
For special needs, aggregates with lighter or heavier density can be used to make
correspondingly lightweight and heavyweight concretes. Generally, the aggregates with bulk
densities less than 1120kg/m3
are called lightweight and those weighing more than 2080
kg/m3
are called heavyweight
For the most part, concrete aggregates are comprised of sand, gravel, and crushed rock derived
from natural sources and, therefore, are referred to as natural mineral aggregates ( are
further classified as granite, limestone, basalt etc. depending upon their parent rock source)
On the other hand, thermally processed materials such as expanded clay and shale, which are
used for making lightweight concrete, are called synthetic aggregates. Aggregates made from
industrial by products, for instance, blast-furnace slag and fly ash, also belong to this category.

7. AGGREGATE CHARACTERISTICS AND THEIR
SIGNIFICANCE
Generally, aggregate properties affect not only the concrete mixture proportions but also the behavior
of fresh and hardened concrete. Due to considerable overlap between the two, it is more appropriate
to divide the study of aggregate properties into three categories that are based on microstructural and
processing factors.
•Characteristics dependent on porosity: density, moisture absorption, strength, hardness, elastic
modulus, and soundness
• Characteristics dependent on prior exposure and processing factors: particle size, shape, and texture
• Characteristics dependent on chemical and mineralogical composition: strength, hardness, elastic
modulus, and deleterious substances present
•A knowledge of certain aggregate characteristics (i.e., density, grading, and moisture state) is required
for proportioning concrete mixtures. Porosity or density, grading, shape, and surface texture determine
the properties of plastic concrete mixtures.
•The mineralogical composition of aggregate affects its crushing strength, hardness, elastic modulus,
and soundness which, in turn, influence various properties of hardened concrete containing the
aggregate.

8. AGGREGATE PROPERTIES
• Absorption capacity is defined as the total amount of moisture required to bring an
aggregate from the oven-dry to the SSD condition.
• SSD condition :When all the permeable pores are full and there is no water film on the
surface, the aggregate is said to be in the saturated-surface dry condition (SSD).
• Surface Moisture: The amount of water in excess of the water required for the SSD
condition is referred to as the surface moisture.
• Specific Gravity :defined as the density of the material including the internal pores.
• Bulk Density :defined as the mass of the aggregate fragments that would fill a unit volume.

9. AGGREGATE PROPERTIES
Soundness:
An aggregate is considered unsound when the volume changes in aggregate induced by
weather (e.g., alternate cycles of wetting and drying, or freezing and thawing) ,result in the
deterioration of concrete.
IS limit:
• Fine Aggregate = 10% (weight loss of five cycles with Na2SO4)
• Fine Aggregate = 15% (weight loss of five cycles with MgSO4)
• Coarse Aggregate = 12% (weight loss of five cycles with Na2SO4)
• Coarse Aggregate = 18% (weight loss of five cycles with MgSO4)
Shape:
• Flakiness Index :Thickness being 0.6 times their mean dimension, contributes more surface
area for a unit volume occupied.
• Elongation Index :Greatest dimension being 1.8 times their mean dimension, contributes
more surface area for a unit volume occupied.

10. AGGREGATE PROPERTIES
Shape:
• Flakiness Index :Thickness being 0.6 times their mean dimension, contributes more surface
area for a unit volume occupied.
Flakiness Index Apparatus Flaky Aggregate

11. AGGREGATE PROPERTIES
Shape:
• Elongation Index :Greatest dimension being 1.8 times their mean dimension, contributes
more surface area for a unit volume occupied.
Elongation Index Apparatus Elongated Aggregate

12. AGGREGATE PROPERTIES
Ideal Aggregate:
Neither Elongated Nor Flaky

13. AGGREGATE PROPERTIES
• Mechanical Properties:
Crushing strength, impact value abrasion resistance, and elastic modulus of aggregate are
interrelated properties, that are greatly influenced by porosity. Aggregates from natural sources
that are commonly used for making normal-weight concrete, are generally dense and strong;
therefore they are seldom a limiting factor to strength and elastic properties of concrete.
Indian Standard (IS) limit:
• Crushing and Impact Value :
Wearing surface = 30% & Non-wearing surface = 45%.
• Abrasion Resistance :
Wearing surface = 30% & Non-wearing surface = 50%.
• Fineness Modulus: Empirical factor called the fineness modulus is often used as an index of the fineness of
aggregate.
The fineness modulus is computed from screen analysis data by adding the cumulative percentages of
aggregate retained on each of a specified series of sieves, and dividing the sum by 100. The sieves used for
determining the fineness modulus are: No. 100 (150 µm), No. 50 (300 µm), No. 30 (600 µm), No. 16 (1.18
mm), No. 8 (2.36 mm), No. 4 (4.75 mm), 10 mm,20mm,40mm etc.
• Slit Content :Material finer than 75-µm (No. 200) sieve are generally called slit. They affect the workability
as water demand increases, strength is also influenced along with bonding. IS limit is 3% by weight.

14. AGGREGATE PROPERTIES
Size and Grading :
• Grading is the distribution of particles of a granular material among various size ranges, usually
expressed in terms of cumulative percentage larger or smaller than each of a series of sizes of sieve
openings, or the percentage between certain range of sieve openings.
• Size: The maximum size of aggregate is conventionally designated by the sieve size on which 15 percent
or more particles are retained. In general, the larger the maximum aggregate size, the smaller will be
the surface area per unit volume which has to be covered by the cement paste of a given water-cement
ratio.
Since the price of cement may be 10 to 15 times as much as the price of aggregate, any action that
saves cement without reducing the strength and workability of concrete can result insignificant
economic benefit
• There are several reasons for specifying grading limits and maximum aggregate size, the
most important being their influence on workability and cost.
For example, very coarse sands produce harsh and unworkable concrete mixtures, and very
fine sands increase the water requirement (therefore, the cement requirement for a given
water-cement ratio) and are uneconomical.
• Aggregates that do not have a large deficiency or excess of any particular size produce the
most workable and economical concrete mixtures.

15. AGGREGATE PROPERTIES
IS Sieve
Size (mm)
Weight
Retained (gms)
Cum.Weight
Retained (gms)
%
Retained
%
Passing
10 0 0 0 100
4.75 120 120 4 96
2.36 450 570 19 81
1.18 390 960 32 68
0.600 870 1830 61 39
0.300 750 2580 86 14
0.150 360 2940 98 2
Pan 60 3000 - -
Fineness Modulus = Col.04/100 = 300/100 = 3
As per our experience Fine Aggregate with F.M of 2.7 to 3.0 are best suited concrete
application
Fineness Modulus (F.M) solved example :

16. CONCLUDING REMARKS
• Aggregate primarily acts as a inert filler, but has secondary influences on various concrete
properties.
• Awareness about the role played by aggregate in concrete can be instrumental in exploiting the
use of the same in achieving concrete properties as per intended requirements, which would be
of high performance and economical.
• It is inappropriate to treat the aggregate with any less respect than cement.

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