Determination Of Soundness Of Aggregates

STANDARD

  • IS:2386(Parts) 1963.

OBJECTIVE

  • To determine the soundness of aggregates.

APPARATUS

  • Sieves of size 80mm, 63mm, 50mm, 40mm, 31.50mm, 25mm, 20mm, 16mm, 12.50mm, 10mm, 8mm, 4,75mm, 4mm, 2.36mm, 1.18mm, 600microns, 300microns and 150microns with square openings conforming to IS: 460-1962.
  • Containers for immersing the saniples shall be perforated so as to permit free access of the solution from the sample and drainage of the solution from the sample with out loss of aggregate.
  • Arrangements shall also be available to ensure that the volume of the solution in which samples are to be immersed shall be at least five times the volume of the sample immersed at any one time.
  • Balance of capacity 500gm sensitivity to 0.01gm
  • Balance of capacity 10kg sensitivity to 1gm.
  • Thermostatically controlled oven capable of being maintained at 105° to 110°C.
  • The rate of evaporation, at this range of temperature shall be at least 25gm/hour for four hours during which period the doors of the oven kept closed. 

Reagents

Sodium Sulphate Solution

  • Prepare saturated solution of sodium sulphate technical grade, conforming to IS: 255 – 1950 or an equivalent grade of the salt of either the anhydrous (Na2 SO4) or the crystalline (Na2 SO410 H20) form in water at temperature of 25 to 30°C.
  • For making of the solution, 420gms of anhydrous salt or 1300gms of decahydrate salt per liter of water are sufficient for saturation at 28°C.
  • The mixer shall be thoroughly stirred during the addition of salt and the solution shall be stirred at frequent  intervals until used.
  • The solution shall be cooled to a temperature of 27 ± 2°C and maintained at that temperature for at least 48 hours before use.
  • Salt cakes if any shall be broken and specific gravity of the solution shall be determined.
  • When used, the solution shall have specific gravity of 1.151 to 1.174.
  • Discoloured solution shall be discarded, or filtered and checked again for specific gravity.

Magnesium Sulphate Solution

  • Prepare saturated solution of magnesium sulphate technical grade, conforming to IS: 257 – 1950 or an equivalent grade of the salt of either the anlaydrous (Mg SO4) or the crystalline (Mg SO4. 7 H20)(Epsom salt) form in water at a temperature of 25 to 30°C.
  • For making of the solution, 400gms of anhydrous salt or 1400gms of heptahydrate salt per liter of water are sufficient for saturation at 28°C. 
  • The mixer shall be thoroughly stirred during the addition of salt and the solution shall be stirred at frequent intervals until used. 
  • The solution shall be cooled to a temperature of 27± 1°C and maintained at that temperature for at least 48 hours before use. 
  • Salt cakes if any shall be broken and specific gravity of the solution shall be determined.
  • When used, the solution shall have specific gravity of 1.295 to 1.308.
  • Discoloured solution shall be discarded, or filtered and checked again for specific gravity.

Fine Aggregates

  • Aggregates passing 4.75 mm IS Sieve shall be considered as fine aggregates.
  • Sample shall be of such size that it will yield not less than 100 gms of each of the sizes shown in Table: 1

Table: 1

Passing IS sieve

Retained on IS sieve

600microns

300microns

1.18mm

600microns

2.36mm

1.18mm

4.75mm

2.36mm

Coarse Aggregates

  • Aggregates of size more than 4.75 mm shall be considered as coarse aggregates.
  • Sample shall be of such size that it will yield not less than following amounts of different sizes, mentioned  in Table: 2 which shall be available in amounts of 5% or more.

All in Aggregates

  • Separate all in aggregates in to two major fractions such as smaller than 4.75 and coarser than 4.75.
  • The former shall be dealt as fine aggregates and the latter as coarse aggregates. 

Preparation of Test Sample

Fine Aggregates

  • Thoroughly, wash fine aggregates on 300 micron IS sieve and dry to constant weight at 105° to 110°C and separate in to different sizes through the sieves mention in Table:1

Coarse Aggregates

  • Thoroughly wash and dry aggregates to a constant weight in an oven at a temperature of 105° to 110°C.
  •  Separate in to desired fraction by sieving through the sieves mention in Table: 2.
  • Weigh the required size of fraction and place in to separate containers.
  • In the case of fraction coarser than 20mm the number of particles shall also be counted.

                Table: 2 

10mm to 4.75mm

300gms

20mm to 10mm
12.5 to 10mm
20 to 12.5mm

l000gms
33%
67%

40mm to 20mm
25mm to 20mm
40 to 25mm

1500gms
33%
67%

63mm to 40mm
50mm to 40mm
63mm to 50mm

3000 gms
50%
50%

80mm and larger sizes by
20mm spread in sieve size, each fraction

3000gms

 PROCEDURE

Storage of Sample in Solution

  • Immerse the samples in the prepared solution of sodium sulphate for not less than 16hours nor more than 18 hours in such a manner that the solution covers the sample to a depth of at least 15 mm.
  • Cover the containers to reduce the evaporation and to prevent accidental condition of extraneous substances.
  • The temperature in the solution shall be maintained Within 27 ± 1°C through out the immersion period.
  • After the immersion period remove the aggregates from the solution and permit to drain for 15 ± 5 minutes and place in the oven at a temperature of 105 to 110°C until it attains a constant weight.
  • During this period remove the aggregates from the oven cool to room temperature and weigh at intervals not less than 4hours nor more than 18hours.
  • Constant weight may considered to have been achieved when two successive weights for any one sample shall not differ by more than 0.1 gram for fine aggregates and l gram for coarse aggregates.
  • After the constant weight has been achieved remove the aggregates from the oven and cool to room temperature.
  • Again immerse the aggregates in solution for next cycle and repeat the same procedure as described above.
  • The number of cycles to be conducted shall be as per specifications.
  • After the completion of the final cycle cool the sample and wash the sample free from sulphate.
  • This may be determined when there is no more reaction of the washed water with barium chloride. (When there is no white precipitation when barium chloride is added to washed water, it can be said that there is no sulphate with washed water) 
  • Dry each faction of sample in an oven at a temperature of 105 to 110°C to constant weight and weigh.
  • Sieve the fine aggregates over the same sieve on which it was retained before the test.
  • Sieve the coarse aggregates over the sieves of sizes shown in Table: 3 for appropriate size of particle.

                Table: 3

Size of aggregates

Sieve Size used to determine loss

63 to 40mm

31.50mm

40 to 20mm

16mm

20 to 10mm

8mm

10 to 4.75mm

4mm

  • Examine visually each size of aggregates to see if there is any evidence of excessive splitting, crumbling or disintegration of the grains.
  • Conduct a combined sieve analysis of all the material subject to the above test to note the variation from the original grain size analysis of the sample.
  • REPORT
    Report the following particulars in the test result
    i. Type of solution used.
    ii. Weight of each fraction of sample before test.
    iii. Material from each fraction of the sample finer than the sieve on which the fraction was retained before test, expressed as a percentage by weight of fraction.

DETERMINATION OF SOUNDNESS OF AGGREGATES
(IS:2836 (Part 5) 1963 

Passing IS sieve (mm) Retained on IS sieve (mm) Gradation of original  sample ( % )    ( A ) Weight of test fraction before test (B) Sieve (mm) to determine loss % Passing finer sieve after test (Actual % loss)  ( C ) Weighted average ( Corrected % loss ) D= (A×C) / 100
FINE AGGREGATES
Total
COARSE AGGREGATES
Total
Note:

In these calculations sizes finer than the 300 microns IS sieve shall be assumed to have zero percent loss.
*The percentage loss (1 1.20%) of the next similar size is used as the percentage loss for this size, since this size contains less than 5% of the original sample which need not to be tested.

Remarks:

 

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