Soundness test determines the disintegration of aggregates due to weathering. This includes freezing, thawing, marine condition etc. However, the weak and porous aggregate shows a change in weight during this soundness test.

Aggregates are the significant factor that contributes adequate strength to concrete.Therefore it is important to obtain the right quality aggregate for construction. 

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Tests on Aggregate

For ensuring the quality of aggregates the following tests are conducted.

• Crushing test
• Abrasion test
• Impact test
• Soundness test
• Water absorption test
• Flakiness index test
• Elongation index test
• Bulk specific gravity test
• Polishing test

Soundness test for aggregates (IS-2386-PART-5)

Aggregate samples are submerged in sodium sulphate or magnesium sulphate solution repeatedly. This process causes salt deposits in the aggregate pores which tends to break the aggregates. After specified number of dipping & drying process the aggregates are sieved to determine the percentage loss of material.

Relevant IS code

• IS: 2386 Part V

Sample selection for fine and coarse aggregates

• The fine aggregate passing through the 10 mm IS sieve should be held as a sample for this test.
• Then sieve the sample again through 10mm, 4.75 mm, 2.36 mm, 1.18 mm, 600 microns, 300 microns.
• However, the sample should be decided in such a way that, it will not yield below 100g of given sizes. 
• For coarse aggregate, sample remove aggregates finer than 4.75 mm. 
• Then dry the sample and again sieve through 80mm, 63mm, 40mm, 20mm, 10mm IS sieves.
• Choose the sample in such a way that, it will not yield below the given amount for the given sizes.
• Weigh the samples separately and store them in different containers.

Apparatus for Soundness test

• IS Sieves (80 mm, 63 mm, 40 mm, 31.5 mm, 25 mm, 20 mm, 16 mm, 12.5 mm, 10 mm, 8.0 mm, 4.75 mm, 4.0 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron, 150 micron)
• Container
• Weighing machine
• Drying oven (105 to 110 degree)

Reagents used

• Sodium sulphate solution
• Magnesium sulphate solution

Test procedure of soundness test

• After the selection of aggregate samples, wash them thoroughly on a 300 micron IS sieve.
• Then dry them at 105 to 110-degree celsius in drying oven.
• After that immerse the sample in a solution of sodium sulphate or magnesium sulphate for 16 to 18 hours. 
• Cover the container for reducing evaporation and accidental addition of extraneous substances. 
• The temperature of the solution should be 27 degree Celsius. 
• After 18 hours, take out the sample and dry them at 105 to 110-degree celsius. 
• Allow them to cool to room temperature and repeat this process.
• After the final cycle, wash the sample and dry them again at 105 to 100-degree celsius.
• Weigh them and sieve them through the same sieve we used before the test.
• The percentage of finer sieve after the test and before the test is determined.
• The percentage loss of weight indicates the soundness of aggregate.