Types of Testing for Aggregates

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TESTING OF AGGREGATES AN OVERVIEW

Aggregates shall be cleaned, hard, dense, durable and frost resistant, shall have a stable moisture content and grading when delivered to the batching plant, and shall not contain iron pyrites, iron oxides, mica, shale, coal or other organic, laminar, soft or porous materials, vitreous aggregates granules or granules with large cavities, or any other substances which may impair the quality of the concrete, attack reinforcing steel or reduce bond. In case of doubt or uncertainty, the effects of suspected harmful substances shall be established by means of tests.
Tests are done as per the BS, BS EN or ASTM standards. Type of the guideline to be followed when testing, could be selected based on the specification. The following test can be identified more commonly in the construction industry.

  1. Grading of fine aggregate.
  2. Grading of coarse aggregate
  3. Organic impurities (fine aggregate)
  4. Aggregate crushing value (ACV)  
  5. Aggregate impact value (AIV)
  6. Flakiness index
  7. Chloride content
  8. Sulphate content
  9. Potential alkali-silica reactivity
  10. Abrasion resistance
  11. Elongation index
  12. Specific gravity, water absorption
  13. 10% fines value
  14. Moisture content
  15. Soundness
  16. Point load test
  17. Surface texture & weathering grade
  18. Loose bulk density                                                           
  19. Grading of aggregate base coarse materials (ABC)
  20. Deleterious materials
  21. Los angeles abrasion Value
  22. Grading of filter materials
  23. Splitting tensile strength for rock core

TESTING OF AGGREGATE CRUSHING VALUE

Aggregate crushing value is an indicator of the crushing resistance of the aggregates when a compressive load is increased. It is tested in accordance with BS 812:110, 1990 and aggregate passing a 14mm test sieve and retained on 10mm sieve are considered for the testing. The allowable range is 17- 41.

TESTING OF FLAKINESS INDEX

The flakiness index of the coarse aggregate is determined as the guidelines stipulated in BS 812 part 1. Aggregate partials are classified as flaky when they have a thickness of less than 0.6 of their mean sieve size. The index is calculated by separating the flaky particles and expressing their mass as a percentage of the mass of the sample tested. The test is not applicable to the material passing a 6.3mm BS test sieve or retained on 63mm BS test sieve. The maximum allowable limit of the flaky particles in the mix is 30%. When it exceeds the limiting value, the mix is considered unsuitable for construction purposes. Flakiness Index = (mass of the flaky particles/mass of the sample) x 100

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