Stripping Test

The stripping is due to the fact that those aggregates which have greater affinity towards water than with bituminous binders and this displacement of bituminous coating from the aggregates depends on the physico-chemical forces acting on the system. In order to ascertain the suitability of coarse aggregates for bituminous road construction, it is desirable to study the stripping or displacement characteristics of the binder from the aggregates, by water.

Stripping Test is conducted as per IS: 6421 – 1971 (Reaffirmed 1998)  

Aim: - To determine the Stripping Value of Road Aggregates.

Apparatus: - Thermostatically controlled water bath, beaker, bowl, mixer etc.

Procedure: -

1.      First of all take 200g aggregate sample which passes through 20mm sieve and retained on   12.5 mm and wash it. Then  the sample is put into Oven for 2-3hr at 150⁰ C

2.      Then take Bitumen 5% of Aggregate Sample and it is heated at 160⁰ C. then the bitumen  sample is taken into a bowl

3.      The aggregate sample is then mixed properly in 10 g (5%) bitumen sample taken in Bowl.

4.      The mixed Sample is taken in a beaker and is placed in air for 2 hrs and then the distilled water (heated at 40⁰ C) is filled in beaker 10mm up of the mixed sample layer. After that it is placed in water bath for 24 hrs.

5.      Then the sample is taken out and visual inspection is done. The Stripping of sample must not exceed 5 %.

      If it happens the anti- stripping agent has to mix with the material is to be used for work.

Observations: -

                 Type of aggregates = CA (passing 20mm sieve & retained on 12.5mm) 

                 Type of binder = Bitumen of grade 30/40

                 % binder used = 5% (Bitumen as binder)

                 Total weight of aggregates = 200g

                 Total weight of binder = 10g

                 Temperature of water- bath = 160⁰C

TABLE 4.5: - Observations of Stripping percentage

Observation Number	Uncovered Area / Stripping Percentage
1	4.8%
2	4.5%
3	4.2%

Mean Stripping Percentage = 4.5%

Result: - Hence the percentage of stripping or uncovered area is less than 5% as per IRC Standards. So aggregate is suitable.