Determination of Clay Lumps in Aggregate, IS 2386 (Part 2)1963

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Update: May 18, 2024

Theory:- There are several tests are performed to determine the physical characteristics of the aggregate to ensure its performance as intended for highway construction. One of these tests is the Determination of Clay Lumps in Aggregate.

Why the Determination of Clay Lumps in Aggregate is Important?

Excessive presence clay lumps in a processed aggregate intended for use in a Portland Cement or Hot Mix Asphalt may interfere with the bonding between the aggregate and cementitious material. This will affect in spalling, raveling, or stripping and create weak points and pop-outs if the material is incorporated into the pavement or structure.

Determination of Clay Lumps in Aggregate, IS 2386 (Part 2)1963

Determination of Clay Lumps in Aggregate, IS: 2386 (Part-2)–1963

Hi friends, you are welcomed in the world of Civil Allied Gyan. Read definition, apparatus, IS code, test procedure, formula, result and lab report of Determination of Clay Lumps in Aggregate as per IS 2386-2-1963.

IS Code for Determination of Clay Lumps:-

IS: 2386 (Part-2)–1963, Estimation of deleterious materials and organic impurities in aggregate.

Apparatus Required For Determination of Clay Lumps:-

The apparatus shall consist of the following:

  1. Balance – A balance or scale sensitive to within 0.1 percent of the weight of the sample to be weighed.
  2. Containers – Containers of a size and shape that will permit the spreading of the sample on the bottom in a thin layer.
  3. Sieves – Sieves conforming to IS: 460-1962, Specification for Test Sieves (Revised).

Sampling the Test Specimen:-

  1. Test samples will be obtained by quartering or by the use of a sampler, from a representative sample selected from the material to be tested.
  2. Test samples will be handled in such a manner as to avoid breaking up clay lumps which may be present in it.
  3. Test samples will be dried to constant weight at a temperature not exceeding 110 °C.
  4. The samples of fine aggregate will consist of particles coarser than 1.18 mm IS Sieve and will weigh not less than 100 g.
  5. The samples of coarse aggregate will be separated into different sizes using 4·75 mm, 10 mm, 20 mm and 40 mm IS Sieves.
  6. The weight of the samples for different sizes will be not less than those indicated below:

Size of Particles making up the sample (in mm)

Weight of sample min. (in g)

Over 4.75 to 10


Over 10 to 20


Over 20 to 40


Over 40


In the case of mixtures of fine aggregates and coarse aggregates, the material will be separated into two sizes on 4.75 mm IS Sieve.

The samples of fine and coarse aggregates will be prepared as described under above paragraph of sampling.

Procedure for Determination of Clay Lumps:-

  1. Spread the sample in a thin layer on a bottom of container and examine for clay lumps.
  2. Break the sample particles with fingers if does, that particles will be classified as clay lumps.
  3. After all discernible clay lumps have been broken, remove the residue from the clay lumps by the use of IS Sieves indicated below:

Size of Particles Making up the Sample (in mm)

Size of Sieve for Sieving Residue of Clay Lumps

Fine aggregate (retained on 1.18 mm lS Sieve)

850 Micron

Over 4.75 mm to 10 mm

2.36 mm

Over 10 mm to 20 mm

4.75 mm

Over 20 mm to 40 mm

4.75 mm

Over 40 mm

4.75 mm


The percentage of clay lumps in aggregates shall be calculated in accordance with the following formula:

Formula to Calculate Clay Lumps in Aggregates:-

Determination of Clay Lumps in Aggregate, IS 2386 (Part 2)1963


L = percentage of clay lumps,

W = weight of sample, and

R = weight of sample after removal of clay lumps.

Reporting of Results:-

The percentage of clay lumps in the aggregate shall be reported to the nearest 0.1 percent.


This method of test (IS: 2386 (Part-2)–1963) covers the procedure for the approximate determination of clay lumps in the routine examination of aggregates.

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