Subgrade Soil

Desirable properties

CBR test

Aggregates

Tests Test Method

Impact Test IS: 2386 Part IV

Crushing Test IS: 2386 Part IV

Specific gravity IS: 2386 Part IIIWater absorption IS: 2386 Part III

Abrasion Test IS:2386 Part IV

Bitumen testsSl.No Tests Test Method Limits Requirements

1 Penetration Test

IS: 1203 - 80-100

2 Ductility Test IS: 1208 Min 75

3 Softening Point Test

IS: 1205 Min 40

4 Specific Gravity IS: 73-1961 Min 0.97-1.02

5 Flash Point IS: 1209 Min 220

Crushing test

Impact test

Abrasion test

Flakiness and elongation Index

Specific Gravity of Aggregates

Requirements of Bitumen

• The bitumen should not be highly temperature susceptible: during the hottest weather the mix should not become too soft or unstable, and during cold weather the mix should not become too brittle causing cracks.

• The viscosity of the bitumen at the time of mixing and compaction should be adequate. This can be achieved by use of cutbacks or emulsions of suitable grades or by heating the bitumen and aggregates prior to mixing.

• There should be adequate affinity and adhesion between the bitumen and aggregates used in the mix.

Tests conducted on bitumen

• Penetration test• Ductility test• Viscosity test• Float test• Specific gravity test• Softening point test• Flash and fire point test• Solubility test• Spot test• Loss on heating test• Water content test

Viscosity of bitumen

Softening Point test

Specific gravity test

Penetration test

Thin Film oven test

Ductility test

Flash and fire point test

• The flash point of a material ia the lowest temp at which the vapour of a substance momentarily takes fire in the form of a flash under specified condition of test.

• Fire point is the lowest temp at which the material gets ignited and burns under specified condition of test.

Cutback bitumen

• Cutback is defined as the bitumen, the viscosity of which has been reduced by a volatile diluent.

• The viscosity of the cutback and rate of which it hardens on the road depend on the characteristics and quantitty of both bitumen and volatile oil used as the diluent.

• Cutback bitumens are available in 3 typesRapid curing (RC)Medium curing (MC)Slow curing (SC)

• RC-2 means it is the rapid curing cutback of grade 2

• RC-0, MC-0, SC-0 are the lowest viscosity cutback bitumen

Bituminous emulsions

• It is the liquid product in which a substantial amount of bitumen is suspended inn a finely divided condition in an aqueous medium and stabilised by means of one or more suitable materials.

• These are used in bituminous road constructions, especially in maintenance and patch repair works. It can be used in wet weather even when it is raining.

• It is also used in soil stabilization, particularly of sands in desert areas.

Tests conducted on Emulsion

• Residue on sieving• Stability to mixing with cement• Stability to mixing with coarse graded

aggregate• Water cement• Sedimentation• Viscosity

Types

• Rapid setting ( surface dressing)• Medium setting (premixing of6-]CA)• Slow setting (FA)