Experiment 4 - Aggregates. ○ 75 % of Volume of Concrete. ○ Classification of
Aggregates. -Fine aggregate. -Coarse Aggregate. IS:383 Definition.
CE 39007 – Concrete Lab Mondays/Thursdays/Fridays
Instructors: Nirjhar Dhang (CE, Monday) Sudhirkumar Barai (CE, Monday) S K Bhattacharyya (CE, Thursday) Biswanath Banerjee (CE, Thursday) Sushanta Chakrabarti (CE, Friday) A George (ARP, Friday)
Experiment 4 - Aggregates
75 % of Volume of Concrete Classification of Aggregates -Fine aggregate -Coarse Aggregate
IS:383 Definition Fine Aggregate – aggregates which passes through 4.75 mm IS Sieve Coarse Aggregate – aggregates which stays in 4.75 mm IS Sieve
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Properties of Aggregate
Particle shape Surface texture Strength of aggregate Specific gravity Bulk density Water absorption and surface moisture Bulking of sand Deleterious substances in aggregates Soundness of aggregate Alkali-aggregate reaction
Experiment 4.A – Sieve Analysis of CA and FA
Sieves – A set of 5 sieves 450 mm diameter – 80,40,20,12.5, 4.75 mm and 5 sieves 200 mm diameter – 2.36, 1.18 mm and 600,300 and 150 micron.
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Fineness Modulus of CA
Fineness Modulus of FA
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Fineness Modulus
Represents the massed average size of the sieve on which material is retained, the sieve being counted from the finest Example – FM = 3 => the third sieve 600 micron is the average size Limits – For Fine sand 2.2 to 2.6 F Medium For M di sand d 2 6 tto 2 2.6 2.9 9 For Coarse sand 2.9 to 3.2 FM > 3.2
Not Acceptable
Grading Curves
Compare the graphs with standard grading curves
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Grading of Fine Aggregates IS Sieve Designation
Percentage passing for Zone 1
Zone 2
Zone 3
Zone 4
10 mm
100
100
100
100
4.75 mm
90-100
90-100
90-100
95-100
Zone 2: Normal sand
2.36 mm
60-95
75-100
85-100
95-100
Zone 3: Fine sand
1.18 mm
30-70
55-90
75-100
90-100
Zone 4: Very fine sand
600 micron
15-34
35-59
60-79
80-100
300 micron
5-20
8-30
12-40
15-50
150 micron
0-10
0-10
0-10
0-15
Zone 1: Coarse sand
Experiment 4.B – Bulking of Fine Aggregate
Presence of moisture content aggregates bulk in volume The moisture particles form a thin film around the aggregates and exert surface tension leads to bulk in volume
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Experiment 4.C – Aggregate Crushing Value for CA Strength of the bulk of aggregate by direct method is impossible - Compressive strength of prepared samples of parent rock - Aggregate crushing value etc.
Experiment 4.C – Aggregate Crushing Value for CA
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Explicit relation between Compressive Strength and Aggregate is NOT AVAILABLE
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Lower the Crushing Value -> Higher the Compressive Strength
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Crushing value > 30% for Road/Pavement Crushing Value > 45% for Structural work
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Experiment 4.D – Absorption of Aggregates • Determination of percentage of absorption of the aggregates • % Absorption
Experiment 4.E – Bulk Density of Aggregates •
The ratio of Loose bulk density/ Compacted bulk density should be between 0.87 to 0.96
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Bulk Density Cement 1440 kg/m3 Sand 1440 kg/m3 to 1600 kg/m3 CA 1600 kg/m3 to 1880 kg/m3
