AGGREGATES FOR CONCRETE
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Aggregates for Concrete
Lecture 3
Contents
Introduction
1
Classification of Aggregates
2
3
4
Aggregate Properties
Test Methods
Introduction
AGGREGATES
Classification of Aggregates
According to Source
Natural Aggregates
Artificial/Synthetic Aggregates
Crushed Stones and Rock, Sand
and Gravel
Fly Ash, Feed stock, etc..
Classification of Aggregates
According to Size
Coarse Aggregates
Fine Aggregates
Crushed Stones and Rock,
Gravel
Sand
Classification of Aggregates
According to Weight
Light weight Aggregates
Heavy Weight Aggregates
Less than 1120 kg/cu.m
Greater than 2100 kg/cu.m
Normal Weight Aggregates
Between 1520-1680 kg/cu.m
Properties of Concrete Aggregates
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Composition
Size and Shape
Surface Texture
Specific Gravity
Bulk Density
Voids
Porosity and Absorption
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Bulking of Sand
Fineness Modulus of Aggregates
Surface Index of Aggregates
Deleterious Materials
Crushing Value of Aggregates
Impact Value of Aggregates
Abrasion Value of Aggregates
Tests for Fine Aggregates
1. Silt Test
2. Colorimetric Test
3. Wash on #200 Sieve
Silt Test
• Silt content is a fine material which is less than
150 micron. It is unstable in the presence of w
ater.
• If we use silty sand for bonding, it will reduce t
he strength and cause rework.
• Excessive quantity of silt, not only reduces the
bonding of cement and fine aggregates but als
o affects the strength and durability of work.
Colorimetric Test for Aggregates
• Determines whether fine aggregates contains injurious
amount of organic matter
• A colour that ranges from light to dark straw indicates
that the amount of organic matter is small. If the colour
ranges from dark to chocolate brown, the aggregate is
not suitable for concrete unless the organic matter is re
moved by washing
Colorimetric Test for Aggregates