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IS 5640:1970 is the Indian Standard (BIS) for method of test for determining aggregate impact value of soft coarse aggregates. This standard outlines the laboratory test method for determining the aggregate impact value (AIV) of soft coarse aggregates. The AIV is a measure of an aggregate's resistance to sudden shock or impact, which is a critical property for materials used in road construction and pavement layers.
Method of test for determining aggregate impact value of soft coarse aggregates
! This test is specifically intended for 'soft' aggregates. For general-purpose coarse aggregates, the procedure in IS 2386 (Part 4) should be followed.
! Ensure the aggregate sample is oven-dried and brought to room temperature before testing to ensure accurate and repeatable results.
! The test result is an empirical value; a higher AIV indicates a weaker aggregate with lower resistance to impact.
BS 812-112:1990British Standards Institution (BSI), United Kingdom
HighWithdrawn
Testing aggregates. Method for determination of aggregate impact value (AIV)
Defines the standard AIV test method, which IS 5640 modifies for soft aggregates.
BS EN 1097-2:2020European Committee for Standardization (CEN), Europe
MediumCurrent
Tests for mechanical and physical properties of aggregates - Part 2: Methods for the determination of resistance to fragmentation
Measures resistance to fragmentation using the Los Angeles test, the preferred method in Europe for the property measured by AIV.
ASTM C131 / C131M - 14American Society for Testing and Materials (ASTM), USA
LowCurrent
Standard Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine
Measures a similar property (toughness/hardness) but uses the Los Angeles abrasion method, not the impact drop-hammer method.
Key Differences
≠The primary difference is the number of blows applied. IS 5640 uses a variable number of blows (e.g., 2, 5, 10, or 15) chosen to produce a percentage of fines between 7.5% and 20%. The standard international equivalent (BS 812-112) uses a fixed number of 15 blows for all aggregate types.
≠IS 5640 is specifically scoped for 'soft coarse aggregates' that would produce excessive fines (>20-30%) under the standard 15-blow test. International standards like BS 812-112 are intended for general-purpose aggregates.
≠The reporting of results differs. IS 5640 requires reporting the 'Aggregate Impact Value (n blows)', where 'n' is the number of blows used. BS 812-112 reports a single 'Aggregate Impact Value (AIV)', which implies a 15-blow test.
≠Modern European practice (EN 1097-2) has largely replaced the impact value test with the Los Angeles (LA) abrasion test, as it is considered to have better reproducibility for assessing aggregate fragmentation resistance.
Key Similarities
≈The fundamental test apparatus, including the impact machine's frame, cylindrical cup, and tamping rod, is identical in its critical dimensions and weight specifications.
≈The basic principle of the test is the same: a prepared aggregate sample is subjected to repeated impacts from a falling weight, and the resulting degradation is measured by the percentage of fines produced.
≈Sample preparation procedures are identical, including the initial aggregate grading (passing 12.5 mm, retained on 10 mm sieve), oven-drying the sample, and filling the measure in three layers with 25 tamps per layer.
≈The calculation of the impact value is the same formula: (weight of fines passing the 2.36 mm sieve / initial weight of the sample) x 100.
Parameter Comparison
Parameter
IS Value
International
Source
Number of Blows
Variable (n), chosen to yield 7.5% to 20% fines
15 (fixed)
BS 812-112:1990
Hammer (Tup) Weight
13.5 to 14.0 kg
13.5 to 14.0 kg
BS 812-112:1990
Height of Hammer Drop
380 ± 5 mm
380 ± 5 mm
BS 812-112:1990
Sieve for Separating Fines
2.36 mm
2.36 mm
BS 812-112:1990
Standard Test Aggregate Size
Passing 12.5 mm, retained on 10.0 mm
Passing 14.0 mm, retained on 10.0 mm (primary size)
BS 812-112:1990
Internal Diameter of Cup
102 mm
102 mm
BS 812-112:1990
Internal Depth of Cup
50 mm
50 mm
BS 812-112:1990
Underlying Test Method
Impact by drop-hammer
Abrasion and impact by tumbling in a drum (Los Angeles Test)
BS EN 1097-2:2020
⚠ Verify details from original standards before use
Key Values7
Quick Reference Values
Test Hammer Weight13.5 to 14.0 kg
Hammer Drop Height380 ± 5 mm
Number of Blows15
Test Sample Sieve Fraction (Passing)12.5 mm
Test Sample Sieve Fraction (Retained)10 mm
Cylinder Internal Diameter102 mm
Final Crushed Material Sieve2.36 mm
Key Formulas
Aggregate Impact Value (%) = (W2 / W1) x 100; where W1 is the initial weight of the sample and W2 is the weight of material passing the 2.36-mm IS Sieve.
To determine the toughness or resistance to fracture under impact for soft coarse aggregates, which is reported as the Aggregate Impact Value (AIV).
What size of aggregate is used for this test?+
The standard test specimen consists of aggregates passing a 12.5 mm IS Sieve and retained on a 10 mm IS Sieve (Clause 5.1).
How many blows are applied during the test?+
The sample is subjected to 15 blows from a hammer weighing 13.5-14.0 kg (Clause 6.3).
What is the difference between this standard and IS 2386 (Part 4)?+
IS 5640 is specifically for soft coarse aggregates, while IS 2386 (Part 4) provides the general method for determining the AIV of standard coarse aggregates. The equipment and basic principle are similar.