Soundness test of aggregates is a crucial evaluation that determines an aggregate’s ability to withstand weathering effects such as wetting, drying, freezing, and thawing. This test helps assess the durability, longevity, and resistance of aggregates used in construction. The soundness test measures the disintegration of aggregates when exposed to simulated weathering cycles, including freezing, thawing, and marine conditions. Weak or porous aggregates often show significant changes in weight during testing. Understanding the soundness of aggregate test is essential for ensuring reliable material performance in infrastructure projects. As aggregates contribute major strength to concrete, selecting quality materials is vital. The soundness test procedure described in IS 2386 Part 5 and ASTM standards often uses sodium sulphate or magnesium sulphate solutions to replicate harsh environmental conditions and highlight the importance of maintaining aggregate quality in construction applications.

We will explore the soundness test on aggregate in this article. We will focus on the methodologies outlined in IS 2386 Part 5 and American Society for Testing and Materials (ASTM) standards.

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

This article is about the soundness test on aggregate. We will focus on the methodologies in IS 2386 Part 5. We will also follow relevant American Society for Testing and Materials (ASTM) standards.

Significance of soundness test for aggregate

This section explores the importance of the soundness test on aggregate.

Durability Assessment

The soundness test on aggregate evaluates its resistance to deterioration due to freezing and thawing cycles. It also assesses its resistance to repeated wetting and drying. This test ensures the aggregate’s longevity in construction applications.

Expansion and Contraction

Moisture absorption and freezing lead to expansion and contraction of aggregates. This can weaken structures, emphasizing the need for the aggregate soundness test to identify potential vulnerabilities.

Preventing Structure Failure

The soundness of aggregate test is essential for confirming that aggregates can withstand environmental stresses. This capability prevents structural failure. It ensures long-term stability and durability in construction projects.

Construction Material Selection

Results from the IS 2386 Part 5 soundness test guide engineers and contractors. They help in choosing appropriate aggregates for specific construction applications. This promotes effective material selection and enhances overall project quality.

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

The sodium sulphate test and magnesium sulphate soundness test measure aggregate durability by evaluating deterioration from salt crystallization cycles inside pore structures.

For this test samples are immersed in sodium sulphate or magnesium sulphate solutions multiple times. Salt deposits form within the aggregate’s pores due to this repetitive process. These deposits cause internal pressure that can weaken and break the aggregates. After a specified number of cycles of dipping and drying, workers sieve the aggregates. This process assesses the percentage of material loss. This procedure, outlined in IS 2386 Part 5, is crucial for conducting a successful aggregate soundness test. It ensures the durability and longevity of aggregates in construction applications.

Relevant IS code

• IS: 2386 Part V
• ASTM C88

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.

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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 on aggregate

• 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.

Soundness test on Aggregate as per ASTM C88

The soundness test on aggregate using ASTM C88 assesses how well aggregates resist weathering. It subjects them to alternate cycles of immersion in a sulfate solution and drying. This test simulates natural conditions where aggregates are exposed to wetting, drying, freezing, and thawing, helping determine their durability. This procedure involves immersing aggregate samples in either sodium sulphate or magnesium sulphate solutions for 16 to 18 hours. Workers dry the aggregates at 105°C to 110°C after soaking them, then cool them to room temperature and repeat this cycle, typically five times to simulate environmental conditions.

After the cycles, the samples are sieved, and the percentage loss in mass is calculated to assess the aggregate’s soundness. The higher the loss in mass, the less durable the aggregate. The aggregate soundness test per ASTM C88 helps engineers select durable aggregates. These aggregates are reliable for use in construction projects under harsh environmental conditions.

Conclusion

The soundness test on aggregate is an essential procedure used to evaluate an aggregate’s ability to withstand long-term weathering effects. This test ensures the aggregate maintains structural integrity when exposed to harsh environmental conditions. Defined in IS 2386 Part 5 and ASTM C88, the method involves submerging aggregate samples in Sodium Sulphate or magnesium Sulphate solutions. These salts simulate real-world cycles of freezing, thawing, heating, and drying. After a specified number of cycles, the aggregates are dried, sieved, and the percentage loss of material is measured. This measurement identifies aggregates that may deteriorate under field conditions. Soundness testing is vital, ensuring only durable and reliable aggregates are used in construction projects, ultimately enhancing the longevity of infrastructure.