SOUNDNESS TEST

(AASHTO T 104, ASTM C 88)

OBJECT: TO DETERMINE THE SOUNDNESS OF THE GIVEN AGGREGATE

SAMPLE.

PERFORMANCE OBJECTIVE:

Upon Successful completion of this lab experiment, the student will able to:

• Determine the aggregate soundness of the road aggregate which gives an idea of the resistance of aggregates to weathering action.
  
• Assess the durability of the aggregates.
  

EQUIPMENT:

1. Containers for aggregates with suitable perforations or with wire mesh to permit free access and drainage of the solution from the sample.
   
2. Thermostatically controlled drying oven maintained at a temperature of 105 ⁰C to 11 ⁰C and having an average rate of evaporation of at least 25 g.
   
3. Sieves as 4:75, 8.0, 10.0, 12.5, 16.0, 20.0, 25.0, 31.0, 40.0, 50.0, 63.0, 80.0 mm.
   
4. A balance of capacity of 5 kg to weigh accurately to at least 1g is needed.
   
5. A device for regulating the temperature of the samples during immersion with salt solution.
   

DISCUSSION:

The test is desired to study the resistance of aggregates to weathering action. In the absence of adequate information from performance studies, a laboratory test simulating accelerated weathering conditions is carried out to judge the durability or soundness of the road aggregates.

In order to quicken the effect of weathering due to alternate wet-dry and freeze-thaw cycles in the laboratory, the resistance to the disintegration of aggregate is determined by soaking the aggregate specimen in a saturated solution of sodium sulphate or magnesium sulphate.

PROCEDURE:

1. Prepare the solution of sodium sulphate maintain the temperature of the solution at 27⁰C ± 2⁰C and stir it at frequent intervals until it is used.
   
2. At the time of use, the solution should have a specific gravity of not less than 1.151 and not greater than 1.171, and dis coloured solution should not be used.
   
3. It may be necessary to use not less than 420g of salt per litre of water.
   
4. Select the sample from the given table
   

SIEVE SIZES

1. Thoroughly wash and dry the sample of coarse aggregate to a constant weight at 105⁰C to 110 ⁰C.
   
2. Take the different samples for each fraction, weigh and place them in separate containers for different containers for test.
   
3. Immerse the sample in the prepared solution of sodium sulphate or magnesium for 16 to 18 hours in such a manner that the solutions cover them to a depth of at least 15 mm.
   
4. Cover the containers to reduce evaporation and during the period of immersion, the temperature of solution is maintained at 27⁰C±2⁰C.
   
5. After the immersion period, the aggregates are removed from the solution, drained for about 15 minutes and placed in the drying oven maintained at a temperature of 105⁰C to110°C.
   
6. Again immerse the aggregates in the prepared solution. For the next cycle of immersion and drying. The cycles of immersion are decided by specifications.
   

1. After completion of the final cycle. The sample is cooled and washed from the sulphate.
   

1. Each fraction of the sample is then dried to a constant temperature of 105 ⁰C to 110 ⁰C and weighed.
   

APPLICATIONS:

The soundness test is useful to assess the resistance of the aggregate to weathering. For cement concrete likely to be exposed to the action of frost, coarse and fine aggregates should pass an accelerated soundness test specified above.

For a general guide, it may be taken that ‘the average loss of the aggregate after 10 cycles should not exceed 12 per cent when tested with sodium sulphate and 18 per cent when tested with magnesium sulphate.

Aggregate with 12 per cent as the maximum permissible loss in soundness test after 5 cycles with sodium sulphate may be used in Bituminous surface dressing, Penetration Macadam and Bituminous Macadam constructions.

RESULT:

COMMENTS: