Conducting Soundness test on Aggregates

Soundness test on Aggregates (IS 2386 Part 5 )

Soundness of aggregates is the resistance possessed by the aggregates against the weathering agencies.To quicken this weathering action due to alternate wetting and drying and freezing thawing saturated solution of sodium sulphate or magnesium sulphate are used.

Apparatus

Sample, Weighing balance up to capacity 500 g (Least count 0.1 g), Weighing balance up to capacity 5000 g (Least count 1 g), Oven, Sieves, 80 mm, 63 mm, 40 mm, 31.5 mm, 25 mm, 20 mm, 16 mm, 12.5 mm, 10 mm, 8.0 mm, 4.75 mm, 4.0 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron, 150 micron, Chemicals Sodium sulphate or magnesium sulphate, Wire mesh bucket, Container

Sample preparation for fine aggregates

1. Make a sieve set with sieves as per the table starting from 10 mm to 300 micron.
2. The amount of sample to be taken for sieving is such that, it will yield not less than 100 g of each of the following sizes.
3. Weigh 100 g of sample from each of the separated fraction and place it in separate containers for the test. 

   

   Sieve set for fine aggregates

 Sample preparation for coarse aggregates

1. 1.Sieve the washed aggregates through 4.75 mm sieve and take the coarse aggregates retained over the sieve.
   2. Sieve the sample through 80,63,40,20,10,4.75  mm sieve and get the yield as per the table given below.
   3.Take the weight and put the sample in individual separate containers.

   

   Sieve set and Yield limits for Coarse aggregates

   
   

   Procedure

   1. 1. Take the individual samples of aggregates and put them in solution of sodium sulphate or magnesium sulphate for about 17 hours in such a way that solution is 15 mm above the aggregates.
      2. Now dry the aggregates and puth them in oven until they obtain constant weight.
      3. Now cool down the aggregates and repeat the first step.
      4. Number of such cycles are decided by the seller and vendor agreement.
      5. After completion of these cycles the aggregates are washed from sodium sulphate solution.And this can be tested by the reaction of the wash water with barium chloride.
      6. Now dry the aggregates and put in oven till they get a constant weight.
      7. After that cool down the aggregates and sieve the fine aggregates on same sieve on which they retained before the test.
      8.  sieve the coarse aggregates on the sieves shown in table below.
      
      

      

      Sieves used to determine loss

       Note:-

      Average weight loss should not exceed 12 percent when tested with 10 cycles of sodium sulphate  and 18 percent  when tested with magnesium sulphate.

      
      
   
   

Determining Flakiness Index of Aggregates

  Flakiness Index of Aggregates (IS:2386 part 1)

Aggregate particles are classified as flaky when they have a thickness (smallest dimension) of less than 0.6 of their mean sieve size. The flakiness index of an aggregate sample is found by separating the flaky particles and expressing their mass as a percentage of the mass of the sample tested. This test is not applicable to aggregate passing 6.30mm sieve and retained as 63.0mm sieve. Flaky particles are considered to be unsuitable for the pavement materials. Flaky particles tends to get broken as the impact loading of vehicles passing over the road.

Apparatus

Sample,Weighing machine, Thickness gauge,Is Sieves of sizes 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 10mm and 6.3mm.

Thickness Gauge

Test Procedure

1. Take the aggregate sample having at least 200 pieces of different sized aggregates.
2. Sieve the sample through mentioned sieves i.e., from 63mm to 6.3mm sieves.
3. Aggregates retained on 63 mm and passing 6.3mm are discarded.
4. Now weigh aggregate retained on different sieve and note down the total weight as “W1”
5. The aggregate particles from each of the size range is taken and passed through corresponding gauge of thickness gauge or flakiness gauge with its thinnest side facing the slot thickness  of gauge.
6. Each gauge length is 0.6 times the mean dimension of aggregate size range. If particle retained on 16mm and passed through 20mm size is taken, then it should pass through 10.8 mm slot of gauge which is 0.6 times the mean of 16mm and 20 mm.(i.e. [{0.6*(16+20)}/2]=10.8 mm
7. The particles that were passing through the length gauge are weighed which is “W2”.
8. Now calculate the flakiness index which is the ratio of weight of particles passed through thickness gauge to the total weight of the sample gauged and it is expressed in percentage.

Calculations:

Elongation index =(W2/W1) X 100

W1= Weight passed of aggregates through thickness gauge
W2= Total sample weight.
Flakiness Index should not more than 15 %  for pavement aggregates material.

Determination of Elongation Index of Aggregates

Elongation Index of Aggregates (IS:2386 part 1)

The elongation index of an aggregate is the percentage by weight of particles whose greatest dimension ( length ) is greater than 1.8 times their mean dimension.For this test aggregates passing 63 mm and retaining at 6.3 mm are taken.The elongation test is not applicable to sizes smaller than 6.3 mm. Elongated particles are considered unsuitable for the pavement. Elongated particles get broken when loaded vehicles pass over the pavement leading weakness of the structure.These particles also create problem in close packing of the aggregates leading to voids in concrete.

Apparatus

Sample,Weighing machine, Length gauge,Is Sieves of sizes 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 10mm and 6.3mm.

Length Gauge

Test Procedure

1. Take the aggregate sample having at least 200 pieces of different sized aggregates.
2. Sieve the sample through mentioned sieves i.e., from 63mm to 6.3mm sieves.
3. Aggregates retained on 63 mm and passing 6.3mm are discarded.
4. Now weigh aggregate retained on different sieve and note down the total weight as “W1”
5. The aggregate particles from each of the size range is taken and passed through corresponding gauge of length gauge or elongation gauge with its longest side facing the width of gauge.
6. Each gauge length is 1.8 times the mean dimension of aggregate size range. If particle retained on 16mm and passed through 20mm size is taken, then it should pass through 32.4mm length gauge which is 1.8 times the mean of 16mm and 20 mm.(i.e. [{1.8*(16+20)}/2]=32.4 mm
7. The particles that were retained on the length gauge are weighed which is “W2”.
8. Now calculate the elongation index which is the ratio of weight of particle retained on length gauge to the total weight of the sample gauged and it is expressed in percentage.

Calculations:

Elongation index =(W2/W1) X 100

W1= Weight retained of aggregates on length gauge
W2= Total sample weight.
Elongation Index should not more than 15 %  for pavement aggregates material.

Specific gravity of fine aggregate (sand) is defined as the ratio of the weight of given volume of aggregates to the weight of equal volume of water at the same temperature.The specific gravity of sands is considered to be around 2.7.

Apparatus

A weighing balance of capacity of about  kg with least count of 0.5 g., an oven with range up to 110ºC,Pycnometer of about 1 litre capacity and 6mm hole at the top, tray, funnel and filter paper etc.

 

Pycnometer Apparatus

Procedure of Test

1. Take about 500g of clean sample of fine aggregates and pour it into the pycnometer.
2. Fill it with distilled water up to brim.Also remove the entrapped air from the container.
3. Clean the outer surface of pycnometer with a clean cloth and weigh it (W1)
4. Empty the pycnometer completely and fill it again with water up to same level and weight it (W2)
5. Drain water from the fine aggregate sample through a filter paper and air dry it.
6. Place the sample inside oven for 24 hours with range of temperature  to 110ºC
7. Cool down the sample and weigh it (W3)

Calculations

Apparent specific gravity = (Weight of dry sample/Weight of equal volume of water )
= W3/(W1-W2)

Calculating the Bulk, apparent Specific gravity and water absorption in coarse aggregates

 Specific Gravity of Coarse Aggregates

It is defined as the ratio of the mass of the solid in given volume of sample to the mass of the equal volume of water at same temperature.It generally varies from 2.6 to 2.9 range. Specific gravity of aggregates generally defines the strength of aggregates . Stones of low specific gravity are generally considered to be weak. The specific gravity helps for choosing right stone for pavement and concrete mixes.It is also useful for the weight volume conversion and calculating the void content in aggregates.In case of Apparent Specific Gravity the volume measurement only includes the volume of the aggregate particle; it does not include the volume of any water permeable voids. The mass measurement only includes the aggregate particle. Apparent specific gravity is intended to only measure the specific gravity of the solid volume, therefore it will be the highest of the aggregate specific gravities. It is formally defined as the ratio of the mass of a unit volume of the impermeable portion of aggregate (does not include the permeable pores in aggregate) to the mass of an equal volume of gas-free distilled water at the stated temperature.In case of Bulk Specific Gravity The volume measurement includes the overall volume of the aggregate particle as well as the volume of the water permeable voids. The mass measurement only includes the aggregate particle. Since it includes the water permeable void volume, bulk specific gravity will be less than apparent specific gravity. It is formally defined as the ratio of the mass of a unit volume of aggregate, including the water permeable voids, at a stated temperature to the mass of an equal volume of gas-free distilled water at the stated temperature.

Apparatus

Weighing machine up to 3 kg capacity, wire basket having mesh size not more than 6.3 mm,oven, container up to 5 liter capacity, soft cloth , tray etc.

Specific gravity apparatus frame setup with wire mesh bucket

Procedure

1. Take about 2 kg of sample and sieve it from 10 mm sieve to remove fines. Now immerse the sample with wire bucket in a water filled container.
2. Immediately after immersion the entrapped air is removed from the sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop at the rate of about one drop per second. The basket and aggregate should remain completely immersed in water for a period of 24 hour afterwards at temperature of 22° – 32°C. 
3.  Now the water is drained out and The basket and  the sample are weighed while suspended in water at a temperature of 22° – 32°C. The weight while suspended in water is noted W1g. 
4. Basket and aggregates are removed from water and allowed to drain for a few minutes after which the aggregates are transferred to the dry absorbent clothes. The empty basket is then returned to the tank of water dipped 25 times and weighed in water W2 g.
5. Aggregates placed on the absorbent clothes are surface dried till no further moisture could be removed by this cloth. Then aggregates are dried for at least 10 minutes until the aggregates are completely surface dry. The surface dried aggregate is then weighed  W3 g.
6. The aggregate is placed in a shallow tray and kept in an oven maintained at a temperature of 110° C for 24 hrs. It is then removed from the oven, cooled in an air tight container and weighted=W4
   
   

Observations and Calculations

Weight of saturated aggregate suspended in water with basket = W1 g.

Weight of basket suspended in water = W2 g.
Weight of saturated surface dry aggregate in air = W3 g.
Weight of oven dry aggregate = W4 g.
Weight of saturated aggregate in water = W₁ – W₂ g
Weight of water equal to the volume of the aggregate = W₃–( W₁–W₂)g

Bulk Specific gravity = W₃ / (W₃– (W₁– W₂))
Apparent specific gravity = W₄/ (W₄– (W₁– W₂))
 Water Absorption = ((W₃ – W₄) / W₄) x 100

Los Angeles Abrasion Test

                       Los Angeles Abrasion Test for Aggregate

Abrasion test is carried out to test the hardness property of aggregates and to decide whether they are suitable for the pavement or not.The principle of Los Angeles abrasion test is to find the percentage wear due to relative rubbing action between the aggregate and steel balls used as per code IS:2386 (Part IV)-1963.

Apparatus

The test sample consists of clean aggregates dried in oven at 105° – 110°C,  Los Angeles Machine, Abrasive charge: Cast iron or steel balls, approximately 48mm in diameter and each weighing between 390 to 445 six to twelve balls are required, Balance of capacity 5 kg or 10 kg, Sieve: 1.70, 2.36, 4.75, 6.3, 10, 12.5, 20, 25, 40, 50, 63, 80 mm IS Sieves. Drying oven,tray.

Procedure

1.  Select the grading to be used in the test such that it conforms to the grading to be used in construction, to the maximum extent possible.Take 5 kg of sample for grading A, B, C & D and 10 kg for grading E, F & G as shown in Table . Table : Number of Spheres as per Gradation of Aggregate.
2.  Choose the abrasive charge as per Table  depending on grading of aggregates. 
3.  Place the aggregates (weighed W1) and abrasive charge on the cylinder and fix the cover. 
4.  Rotate the machine at a speed of 30 to 33 revolutions per minute. The number of revolutions is 500 for grading A, B, C & D and 1000 for gradings E, F & G. 
5.  The machine is stopped after the desired number of revolutions and material is discharged to a tray.
6. The entire stone dust is sieved on 1.70 mm IS sieve. 8. The material coarser than 1.7mm size is weighed (W2) correct to one gram. 

Gradation vs number of spheres of abrasive charge

 

 

 

 

 

 

Calculation:

Original weight of aggregate sample = W1 g

Weight of aggregate sample retained = W2 g 

Weight passing 1.7mm IS sieve = W1 – W2 g

 Abrasion Value = (W1 – W2 ) / W1 X 100

Abrasion Value and Suitability for types of pavement