Determination of Stripping Value of Aggregate Experiment

Objective

To determine the stripping value of aggregates used in road construction; ascertain the suitability of road aggregates for bituminous road construction

IS Standards used:: IS 6241-1971

Need and Scope:This test is conducted to determine the effects of moisture upon adhesion of the bituminous film to the surface particles of the aggregate. This test is of significant value to ascertain the suitability of the two materials i.e., bitumen and aggregates, because one particular aggregate may be satisfactory with one binder and unsatisfactory with another: and the same being true for the binders. The specifications of ministry of the transport and shipping recommend the determination of stripping value by the static immersion method.

Apparatus Required:

1. Thermostatically controlled water bath
2. Beakers of capacity 500 ml

Experimental procedure:

1. Obtain the material that passes through 25mm sieve and is retained on 12.5mm sieve.
2. Dry, clean and heat the binder and aggregates to 150 to 175°C and 120-150°C respectively and mix with 5 percent binder by weight of aggregate.
3. After complete coating, allow the mixture to cool at room temperature in a clean dry beaker.
4. Add distilled water to immerse the coated aggregates.
5. Cover the beaker and keep it undisturbed in a thermostatic water bath at a temperature of 4°C for a period for 24 hrs.
6. Estimate the extent of stripping by visual examination while the specimen is still under water and express as the average percent area of aggregate surface uncoated.

Precautions:

1. The aggregates should be thoroughly dried before mixing the binder.
2. Distilled water should be used for the test
3. Mix - up of the two separate samples should be uniform.

Observation and calculations:

Viva Questions

1. Two aggregates A and B have stripping value of 20% and 30 % when used with the same bitumen; which is preferable and why?
2. How will the stripping value be effected in case the aggregate are not fully dried?