SCOPE
For the determination of dry density of soil when water is added into the sample of soil , it becomes easier for soil particles to move over another particle after applying external forces or compactive force . Owing to that the soil particles come closer & closer hence voids are reduced ultimately which causes the dry density to increase. As we go on increasing the water content , the soil particles creates larger water films around them.
Owing to that dry density goes on increasing till a stage is reached where water starts occupying the space which have been occupied by the soil particle. At this stage achieved density is called maximum dry density. For any compacted soil there is certain moisture content at which soil can be compacted at maximum instant.
In MORT&H specification following tolerances has been given while carrying out the compaction test.
1.EMBANKMENT: As per MORT&H 5th Revision compaction requirement is 95% of dry density & moisture requirement is 1% above and 2% below of OMC. For example if OMC is 11% range will be 9 % to 12% •
2.SUBGRADE: As per MORT&H 5th Revision compaction requirement is 97% of dry density & moisture requirement is 1% above and 2% below of OMC. For example if OMC is 11% range will be 9 % to 12% •
3.GRANULAR SUB BASE(GSB): As per MORT&H 5th Revision compaction requirement is 98% of dry density & moisture requirement is 1% to 2% below of OMC. For example if OMC is 11% ; range will be 11 % to 9% •
4.WET MIX MACADAM: As per IRC 109 – 2015 compaction requirement is 100% of dry density & moisture requirement is 2% above and 2% below of OMC. For example if OMC is 11% ; range will be 9% to 13% 0f OMC.
5.CEMENT TREATED BASE & SUBBASE: As per MORT&H 5th Revision compaction requirement is 98 % of dry density & moisture requirement should not be more 2% OMC. For example if OMC is 11% range will be 11 % to 13%.
Reference :
1.MORT&H 5th Revision
2.IRC 109 -2015
VARIATION IN 95% OF DRY DENSITY