You are all aware that aggregates occupy 70 to 80% of the total volume of concrete.
The fine aggregates are used as filler material & the coarse aggregate are used in concrete to increase the compressive strength of the concrete.
The size of the aggregates influences the bondage of the concrete ingredients. Improper size & quality of aggregates impacts the strength & durability of aggregate.
The grading of aggregates is the determination of the aggregate size used for construction works.
The coarse aggregate is graded as per its size (10mm, 12mm & 20mm). The selection of the right coarse aggregate size depends on the specific construction activity.
In poorly graded concrete, single size aggregates are used in concrete. So cement paste can’t induce good bondage between the material. The result is that the concrete loses its strength & it is easily breakable.
The aggregates are graded as per IS code 383, when the aggregate size is less than 4.75mm is called fine aggregate & more than 4.75mm is called coarse aggregate.
The aggregate gradation is determined by the fineness modulus method where aggregates are passing through the sieve as per IS standard to classify its size.
The aggregates are classified based on,
We have discussed the classification of aggregates already.
The grading limit for single sized coarse aggregate and graded coarse aggregate of nominal size has been listed as per IS standard.
IS Sieve Designation | Percentage passing for single sized aggregates of nominal size(mm) | Percentage passing for single sized aggregates of nominal size(mm) | ||||||||
63 mm | 40 mm | 20 mm | 16 mm | 12.5 mm | 10 mm | 40 mm | 20 mm | 16 mm | 12.5 mm | |
80 mm | 100 | – | – | – | – | – | 100 | – | – | – |
63 mm | 85 – 100 | 100 | – | – | – | – | – | – | – | – |
40 mm | 0 – 30 | 85 – 100 | 100 | – | – | – | 95 -100 | 100 | ||
20 mm | 0 – 5 | 0 – 20 | 85 – 100 | 100 | – | – | 30 – 70 | 95 – 100 | 100 | 100 |
16 mm | – | – | – | 85 – 100 | 100 | – | – | – | 90 – 100 | – |
12.5 mm | – | – | – | – | 85 – 100 | 100 | – | – | – | 90 – 100 |
10 mm | 0 – 5 | 0 – 5 | 0 – 20 | 0 – 30 | 0 – 45 | 85 – 100 | 10 – 35 | 25 – 55 | 30 – 70 | 40 – 85 |
4.75 mm | – | – | 0 – 5 | 0 – 5 | 0 – 10 | 0 – 20 | 0 – 5 | 0 – 10 | 0 – 10 | 0 – 10 |
2.36 mm | – | – | – | – | – | 0 – 5 | – | – | – | – |
The grading of fine aggregates has been listed as per the IS code standards
IS Sieve Designation | Percentage Passing | |||
Grading
Zone I |
Grading
Zone II |
Grading
Zone III |
Grading
Zone IV |
|
10 mm | 100 | 100 | 100 | 100 |
4.75 mm | 90 – 100 | 90 – 100 | 90 – 100 | 95 – 100 |
2.36 mm | 60 – 95 | 75 – 100 | 85 – 100 | 95 – 100 |
1.18 mm | 30 – 70 | 55 – 90 | 75 – 100 | 90 – 100 |
600 microns | 15 – 34 | 35 – 59 | 60 – 79 | 80 – 100 |
300 microns | 5 – 20 | 8 – 30 | 12 – 40 | 15 – 50 |
150 microns | 0 – 10 | 0 – 10 | 0 – 10 | 0 – 15 |
Happy Learning 🙂
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