What does dash implies in table 7 of IS 383? I mean there are blank spaces filled with dashes. What should we understand from that?
What does dash implies in table 7 of IS 383?
- Thread starter D.Nagnur
- Start date
Dnyan Deshmukh
Staff member
Table number 7 shows the percentage passing limits for varying size of aggregates with single size and graded type aggregates category.
Column 2 shows the sieve sizes, against which the limits are given
The aggregates sizes are mentioned in column 3 to 12 has different sizes.
Now look at the row 1, it specify the limit for percentage retained on sieve size 80mm, if you check the limit for this sieve in column number 8 which is for 10mm single size aggregate, you will see a Dash "-", this simply means there is no limit to specify for 80 mm size when you are doing gradation of the 10mm size aggregates.
Practically speaking, we never use all those sieves to do sieve analysis for each type of aggregates but we ensure the set of sieves should consist of all sieves which has a limit specified for that particular size of aggregate which need to be sieved.
Now look at the 10mm single size aggregates column, it has following limit specified,
My size of aggregate is 10mm, if i need to check, i will max go 1 size higher during my test i.e. - 12.5 mm, in table we have a % passing limit of 100%, means nothing should get retained on 12.5 mm sieve, all materials shall pass through.
Practically i am not going to sieve this materials from 80 mm size sieve, so here that dash represent, even if i say 100% should pass from 80 mm size sieve, doing this will only increase your efforts and test time with no positive output as we all know, 10 mm will always pass from a very high size hole on sieve.
Now taken another example of 20 mm
Now here it has stated a limit of 100% passing from a 40mm size sieve, as we know it can pass easily, i can use 25mm sieve to check oversize particles instead of 40 mm.
As the limits are not specified for16 mm and 12.5 mm sieves, i will not use those sieves while doing sieve analysis.
So the dash can mean, there are no limits specified for a size of aggregates on this size of sieve.
Column 2 shows the sieve sizes, against which the limits are given
The aggregates sizes are mentioned in column 3 to 12 has different sizes.
Now look at the row 1, it specify the limit for percentage retained on sieve size 80mm, if you check the limit for this sieve in column number 8 which is for 10mm single size aggregate, you will see a Dash "-", this simply means there is no limit to specify for 80 mm size when you are doing gradation of the 10mm size aggregates.
Practically speaking, we never use all those sieves to do sieve analysis for each type of aggregates but we ensure the set of sieves should consist of all sieves which has a limit specified for that particular size of aggregate which need to be sieved.
Now look at the 10mm single size aggregates column, it has following limit specified,
IS Sieve Size | % Passing Limit for 10mm Single Size Aggregates |
|---|---|
80 mm | - |
63 mm | - |
40 mm | - |
20 mm | - |
16 mm | - |
12.5 mm | 100 |
10 mm | 85 to 100 |
4.75 | 0 to 20 |
2.36 | 0 to 5 |
My size of aggregate is 10mm, if i need to check, i will max go 1 size higher during my test i.e. - 12.5 mm, in table we have a % passing limit of 100%, means nothing should get retained on 12.5 mm sieve, all materials shall pass through.
Practically i am not going to sieve this materials from 80 mm size sieve, so here that dash represent, even if i say 100% should pass from 80 mm size sieve, doing this will only increase your efforts and test time with no positive output as we all know, 10 mm will always pass from a very high size hole on sieve.
Now taken another example of 20 mm
IS Sieve Size | % Passing Limit for 10mm Single Size Aggregates |
|---|---|
80 mm | - |
63 mm | - |
40 mm | 100 |
20 mm | 85 to 100 |
16 mm | - |
12.5 mm | - |
10 mm | 0 to 20 |
4.75 | 0 to 5 |
2.36 | - |
Now here it has stated a limit of 100% passing from a 40mm size sieve, as we know it can pass easily, i can use 25mm sieve to check oversize particles instead of 40 mm.
As the limits are not specified for16 mm and 12.5 mm sieves, i will not use those sieves while doing sieve analysis.
So the dash can mean, there are no limits specified for a size of aggregates on this size of sieve.
Superb explanation. Really great
Now to draw conclusion for 20mm aggregate seive analysis is that
# i can omit 40 mm seive and use 25mm for checking oversize aggregate.
# i can omit seive 16mm , 12.5mm and even 2.36mm.
Right???
Dnyan Deshmukh
Staff member
Yes because 25mm is still higher size and passing through 40mm 100% means it should also pass 100% from 25mm sieve.
Due to the metric and imperial unit system, manufacturer might order a wrong size mesh for production of aggregate like instead of 20mm they might fix the mesh of 1" or instead of 10mm they might fix mesh of 1/2".
To ensure manufacturer has right set of mesh installaed at production unit, to verify the correct size, always better to add a 1 size higher sieve in your sieve analysis test.
When there are no specs for them you can omit them.
For advancement in concrete, you may add them and set your own limits depending on what you are trying to achieve and you have created limit for all in aggregates grading ( graded aggregates, which you make by combining all single size aggregates in one including FA for doing concrete production)
All in aggregate grading done to set % of each size to ensure it falls within limit to make cohesive mix.
Like FA%:10mm%:20mm% for mix design.
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