CRUSHING VALUE



DETERMINATION OF AGGREGATE CRUSHING VALUE 

IS: 2386 - Part 4 

1. Introduction

The aggregate crushing value (ACV) gives a relative measure of the resistance of an aggregate to crushing under a gradually applied load. If the ACV is greater than or equal to 30, the result may be anomalous, and in such cases the „ten percent fines value (TFV)? should be determined instead. The standard aggregate crushing test shall be made on aggregates passing through 12.5 mm IS sieve and retained on a 10 mm IS Sieve. If the standard size is not available, other sizes up to 25 mm may be tested.

2. Apparatus

(i) A 15 cm diameter open-ended steel cylinder, with plunger and base-plate.

(ii) IS Sieves of sizes 12.5, 10 and 2.36 mm.

(iii) A compression testing machine capable of applying a load of 40 tonnes.

(iv) Tamping rod.

(v) Balance.

(vi) Cylindrical measure

3.  Procedure

a) Aggregate passing 12.5 mm IS Sieve and retained on 10-mm IS Sieve, are oven-dried at a temperature of 100 to 110°C and then cooled to room temperature before testing.

b) The required quantity of test sample is obtained by filling the cylindrical measure in 3 equal layers and tamping each layer 25 times with the tamping rod. The top is levelled using the tamping rod as a straight edge.

c) The weight of the test sample should be determined (Weight A) and the same weight of sample shall be taken for the repeat test.

d) The test sample is transferred into the cylinder of the test apparatus in 3 layers and each layer is tamped with 25 strokes of the tamping rod.

e) The surface of the aggregates is then leveled and the plunger inserted.

f) The apparatus with the test sample and plunger in position is then placed in the compression testing machine and loaded at a uniform rate so as to achieve 40 tonnes load in 10 minutes. After this, the load is released.

g) The sample is then sieved through a 2.36 mm IS Sieve and the fraction passing through the sieve is weighed (Weight B).

4. Calculation

The ratio of the weight of fines formed after applying the standard load to the total sample weight in each test shall be expressed as a percentage.

The result must be recorded to the first decimal place. Aggregate crushing value = [B/A] x100,  

where B = Weight of fraction passing the appropriate sieve.

A = Weight of oven dry sample.

5.  Reporting of results

The mean of the two results shall be reported to the nearest whole number as the „aggregate crushing value?. The size of material tested, shall also be stated. 

DETERMINATION OF TEN PERCENT FINES VALUE 

IS: 2386 - Part 4

1. Introduction

The „ten percent fines? value gives a measure of the resistance of an aggregate to crushing, that is, applicable to all aggregates. This method illustrates the procedure to determine the „ten percent fines? value of coarse aggregates.

2. Apparatus

(i) A 15 cm diameter open-ended steel cylinder, with plunger and base-plate.

(ii) IS Sieves of sizes 12.5 mm, 10 mm and 2.36 mm.

(iii) A compression testing machine capable of applying a load up to 50 tonnes in a period of 10 minutes.

(iv) Tamping rod 16 mm diameter, 45 cm to 60 cm long with one end rounded.

(v) Balance of capacity 3 kg readable and accurate to 1 gm.

(vi) Cylindrical measure of internal diameter 115 mm and 180 mm height, for measuring the sample.

(vii)  Dial gauge.

3. Procedure

a) Aggregate passing 12.5 mm IS Sieve and retained on 10 mm IS Sieve, are oven-dried at a temperature of 100 to 110°C and then cooled to room temperature before testing.

b) The required quantity of test sample is obtained by filling the cylindrical measure in 3 equal layers and tamping each layer 25 times with the tamping rod. The top is levelled using the tamping rod as a straight edge. The quantity of aggregate shall be such that the depth of material in the cylinder, after tamping shall be 10 cm.

c) The weight of the test sample should be determined (Weight A) and the same weight of sample shall be taken for the repeat test.

d) The test sample is transferred into the cylinder of the test apparatus in 3 layers and each layer is tamped with 25 strokes of the tamping rod.

e) The surface of the aggregates is then leveled and the plunger inserted.

f) The apparatus, with the test sample and plunger in position is then placed in the compression testing machine and loaded at a uniform rate so as to cause a total penetration of the plunger in 10 minutes of about:

(i) 15.0 mm for rounded or partially rounded aggregates (for example, uncrushed gravels),

(ii) 20.0 mm for normal crushed aggregates, and

(iii) 24.0 mm for honeycombed aggregates (for example, expanded shale and slag). 

NOTE: These figures may be varied according to rounding or honey combing.

g) The sample is then sieved through a 2.36 mm IS Sieve and the fraction passing through the sieve is weighed (Weight B) and is expressed as a percentage of the weight of the test sample. 

NOTE: Normally, this percentage will fall within the range 7.5 to 12.5. If it does not, a further test shall be made at a load adjusted to bring the percentage fines within the range of 7.5 to 12.5.

4. Calculation

Load required for 10 percent fines = (14 x A)/(B+4)   where            

A = load in tonnes and  

B = mean percentage fines from two tests at „A? tonnes load.

5. Reporting of results

For loads greater than 10 tonnes, the load required to produce 10 percent fines shall be reported to the nearest whole number and for loads less than 10 tonnes the result shall be expressed to the nearest 0.5 tonne.

DETERMINATION OF SOUNDESS OF AGGREGATES 

IS: 2386 - Part 4 

1. Introduction

This test furnishes information helpful in judging the performance of aggregates against weathering action, particularly when adequate information is not available from service records of the material exposed to actual weathering conditions. In soundness test, the resistance to disintegration of aggregates by saturated solutions of sodium sulphate or magnesium sulphate is determined.

2. Apparatus

(i) A balance or scale of capacity not less than 500 gm, readable and accurate to 0.1 gm for weighing fine aggregates.

(ii) For weighing coarse aggregates a balance or scale of capacity not less than 5000 gm, readable and accurate to 1 gm.

(iii) Suitable means to regulate the temperature of the samples immersed in sodium sulphate or magnesium sulphate solutions.

(iv) A well ventilated oven, thermostatically controlled, to maintain a temperature of 105  to 110°C with average rate of evaporation of 25 gm/hr for 4 hours.

(v) Baskets made of suitable wire mesh or sieves with suitable openings for immersing the samples of aggregate in the solution.

(vi) IS test sieves given in table 1

Table 1 - Recommended IS test sieves for soundness test

No.

For fine aggregates

For coarse aggregates

1

150 microns

8.0 mm

2

300 microns

10 mm

3

600 microns

12.5 mm

4

1.18 mm

16 mm

5

2.36 mm

20 mm

6

4.00 mm

25 mm

7

4.75 mm

31.5 mm

8

-

40 mm

9

-

50 mm

10

-

63 mm

11

-

80 mm

3. Preparation of Sodium Sulphate solution

a) Saturated solution of sodium sulphate is prepared by dissolving sodium sulphate, technical grade conforming to IS: 255-1950 in water at a temperature of 25°C to 30°C.

b) The mixture is thoroughly stirred during the addition of the salt and the solution is stirred at frequent intervals until used. Sufficient salt is added till excess crystals are present in the solution ready for testing.

c) Normally 350 gm of anhydrous salt or 1150 gm of decahydrate salt per litre of water is sufficient produce saturation at 28°C. Since excess crystals are to be present, this may be increased to 420 gm and 1300 gm respectively.

d) The solution is cooled to a temperature at 27±2°C and maintained at this temperature at least for 48 hours before use.  

e) The grade of sodium sulphate mostly available as dried powder can be conveniently used for the preparation of solution.  

f) The specific gravity of the solution is determined immediately before using for the test. The specific gravity shall not less than 1.151 and not more than 1.174.

g) Discoloured solution is discarded.

4. Preparation of Magnesium Sulphate solution

a) Saturated solution of magnesium sulphate is prepared by dissolving magnesium sulphate, technical grade conforming to IS: 257-1950 in water at a temperature of 25°C to 30°C.

b) The mixture is thoroughly stirred during the addition of the salt and the solution is stirred at frequent intervals until used. Sufficient salt is added till excess crystals are present in the solution ready for testing.

c) Normally 400 gm of anhydrous salt or 1400 gm of heptahydrate salt per litre of water is sufficient to produce saturation at 28°C. Since excess crystals are to be present, 1600 gm of heptahydrate salt per litre of water is recommended for use.

d) The solution is cooled to a temperature at 27±1°C and maintained at this temperature at least for 48 hours before use.

e) The grade of sodium sulphate mostly available as dried powder can be conveniently used for the preparation of solution.  

f) The specific gravity of the solution is determined immediately before using for the test. The specific gravity shall not less than 1.295 and not more than 1.308.

g) Discoloured solution is discarded.

5. Sample preparation

5.1 Fine aggregates

a) The fine aggregates for the test shall pass through 10 mm IS sieve.

b) Samples of the size ranges indicated in table 2 are prepared with each size not less than 100 gm. 

Table 2 – Recommended sizes of samples for fine aggregates. 

Passing IS sieve

Retained on IS sieve

600 mic

300 mic

1.18 mm

600 mic

2.36 mm

1.18 mm

4.75 mm

2.36 mm

10 mm

4.75 mm

c) The sample of fine aggregates is washed on a 300 micron sieve, dried to constant weight at 105°C to 110°C and separated into different sizes mentioned in the table above.

d) Samples of 100 gm is weighed after final sieving from each fraction and kept in separate containers for test.

5.2 Coarse aggregates

a) Coarse aggregate samples are prepared for the test after removing the fraction finer than 4.75mm IS sieve.

b) The sample size shall not be less than the amounts given in the table 3 and in excess of 5% or more. 

c) The sample of coarse aggregates is thoroughly washed, dried to constant weight at 105°C to 110°C and separated into different sizes mentioned in the table 3.

d) Samples of required weight is weighed after final sieving from each fraction and kept in separate containers for test.

e) In case of fractions coarser than 20 mm size, the total number of pieces shall also be counted and recorded

Table 3 - Quantity of coarse aggregate sample required for soundness test

IS sieve size (Square-hole sieves)

Required quantity/fraction

10 mm to 4.75 mm

300 gm

20mm to 10mm

1000 gm

Consisting of: 12.5 mm to 10 mm

33%

20 mm to 12.5 mm

67%

40 mm to 20 mm

1500 gm

Consisting of:  25 mm to 20 mm

33%

40 mm to 25 mm

67%

63 mm to 40 mm

3000 gm

Consisting of:  50 mm to 40 mm

50%

63 mm to 50 mm

50%

80 mm and large sizes - each fraction

3000 gm

5.3 All-in aggregates

a) All-in aggregates shall be separated into two major fractions, finer than 4.75 mm and coarser than 4.75 mm.  

b) If the samples contain less than 5% in any of the size range, the same need not be tested. However, the test result of such fraction will be taken as the average of the value obtained for sizes above and below the fraction found to be less than 5%.

6. Procedure

a) The sample of aggregates in the container is immersed in sodium or magnesium sulphate solution at a temperature of 27±1°C with a cover of at least 15 mm of the solution above the top of the aggregates.

b) The containers are covered to reduce evaporation and accidental addition of extraneous materials.

c) The samples are immersed for a period of not less than 16 hours and not more than 18 hours.

d) After the immersion period, the sample is removed from the solution, permitted drain for 15±5 minutes and kept in the oven at 105°C to 110°C.

e) The sample is dried to constant weight at 105°C to 110°C. The sample is taken out of the oven, cooled to room temperature and weight determined every 4 hours till constant weight is achieved.

f) Constant weight is considered to be achieved when two successive weights do not differ by 0.1 gm in the case of fine aggregates and 1 gm in the case of coarse aggregates.

g) After constant weight is achieved, the sample is again immersed in the prepared solution.

h) This process is repeated for the prescribed number of cycles

i) After the end of the final cycle, the sample is washed free from solutions. This is ascertained by the reaction of the wash water with BaCl2.

j) The each sulphate free fraction is dried to constant weight at 105°C to 110°C and the weight recorded.

k) The fine aggregates are sieved through the sieves on which it was retained before test. Coarse aggregates are sieved through sieves mentioned in table 4.

l) The fraction coarser than 20 mm is examined qualitatively and quantitatively. In qualitative examination, the amount of disintegration, splitting, crumbling, cracking, flaking etc are noted and recorded. The numbers of particles affected are also counted

Table 4 – Recommended sieves for determining loss for coarse fraction

Size of aggregates

Sieve to determine loss

63 mm to 40 mm

31.5 mm

40 mm to 20 mm

16 mm

20 mm to 10 mm

8.0 mm

10 mm to 4.75 mm

4.0 mm

m) The fraction coarser than 20 mm is examined qualitatively and quantitatively. In qualitative examination, the amount of disintegration, splitting, crumbling, cracking, flaking etc are noted and recorded. The numbers of particles affected are also counted.

7. Reporting of results

The report shall include the following data:

(i) Weight of each fraction of each sample before test.

(ii) Weight of fraction passing each sieve after test, expressed as a % of the original weight.

(iii) Weighted average of the percentage loss obtained from the product of percentage of each fraction multiplied by the % passing the finer sieve after test. In these calculations, sizes finer than 300 micron IS sieve is assumed as to have zero % loss.

(iv) For particles above 20 mm size, indicate the number of pieces before test and the number of particles affected by test.

(v) The solution used viz., Sodium sulphate or Magnesium sulphate. Typical formats for recording soundness test data for coarse and fine aggregates are given in tables 5 and 6 below: 

Table 5 - Soundness test data for coarse aggregates 

IS sieve passing mm sieveretained mm Grading % of the originalsample Weight of test fraction before test % passing the finer sieve after test Weighted avarage
150 mic - 5 - - -
300 mic 150 mic 11.4 - - -
600 mic 300 mic 26 100 4.2 1.09
1.18 mm 600 mic 25.2 100 4.8 1.21
2.36 mm 1.18 mm 17 100 8 1.36
4.75 mm 2.36 mm 10.8 100 11.2 1.21
10 mm 4.75 mm 4.6 - 11.2* 0.52
TOTAL 100 400 - 5.39

NOTE: The percentage passing for the size is taken as the % passing for the next smaller size since the percentage of this fraction in the test sample is less than %.

Table 6 - Soundness test data for fine aggregates

IS sieve passing mm sieveretained mm Grading % of theoriginal sample Weight oftest fraction before test % passing the finer sieve after test Weightedaverage
63 mm 40 mm 20 3000 4.8 0.96
40 mm 20 mm 45 1500 8 3.6
20 mm 10 mm 23 1000 9.6 2.2
10 mm 4.75 mm 12 300 11.2 1.34
TOTAL 100 5800 - 8.1

NOTE: The sample taken is the minimum specified but larger samples can be used.

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