Soft particles in coarse aggregate | Deleterious materials


This method of aggregate testing covers the process of determination of soft particles ( Deleterious materials) in coarse aggregate on the basis of scratch hardness.

Test Standard : IS 2386-Part 2: 1963

Test Apparatus :

  1. 1.6mm diameter Brass rod with Rockwell hardness of 65RHB to 75RHB inserted into the wood shaft of ordinary lead pencil.
  2. IS Sieves of size 50 mm, 40 mm, 25 mm, 20 mm, 12.5 mm, 10 mm

Test procedure :

  • Take sample by quartering method.
  • Test sample shall consists of all materials from which the size finer than 10mm IS Sieves has been removed. Test sample shall be of such size that it will yield not less than the following quantities of different sizes.

Sample shall be available in amounts of 10% or more:

Sieve Size (mm)Test sample (gms)
Over 10 to 12.5200
Over 12.5 to 20600
Over 20 to 25 1500
Over 25 to 40 4500
Over 40 to 50 12000
Sample weight
  • Each particle of the aggregate under test shall be scratched with brass rod applying about 1kg of pressure.
  • Particles are considered to be soft if a groove is made in them without deposition of metal from the brass rod or if separate particle are detached from the rock mass.
  • Weigh & number of particles of each size of each sample classified as soft in the test (say M1,M2, M3, M4, M5 gms & N1, N2, N3, N4, N5)
  • Weigh & number of particles of each size of each sample tested with brass rod (say m1, m2, m3, m4, m5 gms& n1, n2, n3, n4, n5)

Calculation for Soft particles in coarse aggregate

Soft particles % (by weight) = 100 x (M1+M2+M3+M4+M5)/(m1+m2+m3+m4+m5)

Soft particles % (by Numbers) = 100x (N1+N2+N3+N4+N5)/ (n1+n2+n3+n4+n5)

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Founder & Admin of, I am a civil engineer working as a Assistant Engineer (QA/QC).

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