Determination of Aggregate Abrasion Value

Objective : This method of test methods of determining the abrasion value of coarse aggregate, by the use of Los Angeles machine.

Reference : IS : 2386 ( Part IV) – 1963, IS: 383-1970

Theory : Abrasive Charge-The abrasive charge shall consist of cast iron spheres or steel spheres approximately 48 mm in. diameter and each weight between 390 and 445 g.

The test sample consist of clean aggregate which has been dried in an oven at 105°C to 110°C and it should conform to one of the gradings shown in Table 3.22.

Apparatus :
Los Angeles machine - The Los Angeles abrasion testing machine shall consist of a hollow steel cylinder, closed at both ends, having an inside diameter of 700 mm and an inside length of 500 mm. The cylinder shall be mounted on stub shafts attached to the ends of the cylinders but not entering it, and shall be mounted in such, a manner that it may be rotated about its axis in a horizontal position. An opening in the cylinder shall be provided for the introduction of the test sample. A removable steel shelf, projecting radially 88 mm into the cylinder and extending its full length, shall be mounted along one element of the interior surface of the cylinder. The shelf shall be of such thickness and so mounted, by bolts or other approved means, as to be firm and rigid. The 1.70 mm IS Sieve.

Figure :

Procedure :
1. The test sample shall consist of clean aggregate which has been dried in an oven at 105 to 110°C to substantially constant weight and shall conform to one of the gradings shown in Table 3.22. The grading or gradings used shall be those most nearly representing the aggregate furnished for the work.

2. The test sample and the abrasive charge shall be placed in the Los Angeles abrasion testing machine and the machine rotated at a speed of 20 to 33 rev/min. For gradings A, B, C and D, the machine shall be rotated for 500 revolutions; for gradings E, F and G, it shall be rotated for 1 000 revolutions.

3. The machine shall be so driven and so counter-balanced as to maintain a substantially uniform peripheral speed. If an angle is used as the shelf, the machine shall be rotated in such a direction that the charge is caught on the outside surface of the angle.

4. At the completion of the test, the material shall be discharged from the machine and a preliminary separation of the sample made on a sieve coarser than the l.70 mm IS Sieve.

5. The material coarser than the 1.70 mm IS Sieve shall be washed dried in an oven at 105 to 110°C to a substantially constant weight, and accurately weighed to the nearest gram.

Calculation :
The difference between the original weight and the final weight of the test sample is expressed as a percentage of the original weight of the test sample. This value is reported as the percentage of wear.

Aggregate Abrassion Value=B/A*100

B weight in g of fraction passing through 1.70 mm IS Sievs
A weight in g of saturated surface - dry sample,

Conclusion / Result :
The aggregate Abrasion Value of given sample of coarse aggregate is ……….. %
The percentage of wear should not be more than 16 per cent for concrete aggregates.

Determination of Aggregate Impact Value

Objective : This method of test covers the procedure for determining the aggregate impact
value of coarse aggregate.

Reference : IS : 2386 ( Part IV) – 1963, IS: 383-1970

Theory : The aggregate impact value‘ gives a relative measure of the resistance of an aggregate to sudden shock or impact, which in some aggregates differs from its resistance to a slow compressive load.

Apparatus : An impact testing machine of the general form shown in Fig. 2 and complying with the following:

1. A cylindrical steel cup of internal dimensions: Diameter 102 mm, Depth 50 mm and not less than 6.3 mm thick

2. A metal hammer weighing 13.5 to 14.0 kg, the lower end of which shall be cylindrical in shape, 100.0 mm in diameter and 5 cm long, with a 2 mm chamber at the lower edge, and case-hardened. The hammer shall slide freely between vertical guides so arranged that the lower (cylindrical) part of the hammer is above and concentric with the cup.

3. Means for raising the hammer and allowing it to fall freely between the vertical guides from a height of 380.0 mm on to the test sample in the cup, and means for adjusting the height of fall within 5 mm. Sieves-The IS Sieves of sizes 12.5, 10 and 2.36 mm, Tamping Rod, balance of capacity not less than 500 g, Oven etc.

Procedure : 
1. The test sample shall consist of aggregate the whole of which passes a 12.5 mm IS Sieve and is retained on a 10 mm IS Sieve. The aggregate comprising the test sample shall be dried in an oven for a period of four hours at a temperature of 100 to 110°C and cooled.

2. The measure shall be filled about one-third full with the aggregate and tamped with 25 strokes of the rounded end of the tamping rod. The net weight of aggregate in the measure shall be determined to the nearest gram (Weight A)

3. The impact machine shall rest without wedging or packing upon the level plate, block or floor, so
that it is rigid and the hammer guide columns are vertical.

4. The cup shall be fixed firmly in position on the base of the machine and the whole of the test sample placed in it and compacted by a single tamping of 25 strokes of the tamping rod.

5. The hammer shall be raised until its lower face is 380 mm above the upper surface of the aggregate
in the cup, and allowed to fall freely on to the aggregate. The test sample shall be subjected to a total
of 15 such blows each being delivered at an interval of not less than one second.

6. The crushed‘ aggregate shall then be removed from the cup and the whole of it sieved on the 2.36
mm IS Sieve until no further significant amount passes in one minute. The fraction passing the sieve
shall be weighed to an accuracy of 0.1 g (Weight. B).

7. The fraction retained on the sieve shall also be weighed (Weight C) and, if the total weight (C+B) is less than the initial weight (Weight A) by more than one gram, the result shall be discarded and a
fresh test made. Two tests shall be made.

Calculation :
The ratio of the weight of fines formed to the total sample weight in each test shall he expressed as a
percentage, the result being recorded to the first decimal place:

Aggregate Impact Value=B/A*100

B weight in g of fraction passing through 2.36 mm IS Sievs
A weight in g of saturated surface - dry sample,

Conclusion / Result :
The aggregate Impact value of given sample of coarse aggregate is ……….. %
The aggregate impact value should not be more than 45 percent for aggregate used for concrete other than for wearing surfaces, and 30 percent for concrete used for wearing surfaces such a runways, roads and air field pavements.

Determination of Aggregate Crushing value

Objective:
This method of test covers the procedure for determining the aggregate crushing value of coarse aggregate.

Reference :
IS : 2386 ( Part IV) – 1963, IS: 383-1970

Theory :
The aggregate crushing value‘ gives a relative measure of the resistance of an aggregate to crushing under a gradually applied compressive load. With aggregate of aggregate crushing value‘ 30 or higher, the result may be anomalous, and in such cases the ten percent fines value‘ should be determined instead.

Apparatus:
A 15-cm diameter open-ended steel cylinder, with plunger and base-plate, of the general form and dimensions shown in Fig. ,A straight metal tamping rod, A balance of capacity 3 kg, readable and accurate to one gram, IS Sieves of sizes 12.5, 10 and 2.36 mm, For measuring the sample, cylindrical metal measure of sufficient rigidity to retain its form under rough usage and of the following internal dimensions: Diameter 11.5 cm and Height 18.0 cm.

Procedure :
1. The material for the standard test shall consist of aggregate passing a 12.5 mm IS Sieve and retained on a 10 mm IS Sieve, and shall be thoroughly separated on these sieves before testing.

2. The aggregate shall be tested in a surface-dry condition. If dried by heating, the period of drying shall not exceed four hours, the temperature shall be 100 to 110°C and the aggregate shall be cooled to room temperature before testing.

3. The appropriate quantity may be found conveniently by filling the cylindrical measure in three layers of approximately equal depth, each layer being tamped 25 times with the rounded end of the tamping rod and finally leveled off, using the tamping rod as a straight-edge.

4. The weight of material comprising the test sample shall be determined (Weight A) and the same
weight of sample shall be taken for the repeat test.

5. The apparatus, with the test sample and plunger in position, shall then be placed between the platens of the testing machine and loaded at as uniform a rate as possible so that the total load is reached in 10 minutes. The total load shall be 400 kN.

6. The load shall be released and the whole of the material removed from the cylinder and sieved on a
2.36 mm IS Sieve for the standard test. The fraction passing the sieve shall be weighed (Weight B).

Calculation :
The ratio of the weight of fines formed to the total sample weight in each test shall be expressed as a
percentage, the result being recorded to the first decimal place:
Aggregate Crushing Value =B/A*100
B=weight in g of fraction passing through appropriate sieves
A=weight in g of saturated surface - dry sample,


Conclusion / Result :
The aggregate crushing value of given sample of coarse aggregate is ……….. %
The aggregate crushing value should not be more than 45 percent for aggregate used for concrete other
than for wearing surfaces, and 30 percent for concrete used for wearing surfaces such a runways, roads and air field pavements.

Determination of Flakiness Index and Elongation Index of Coarse Aggregates

Objective : To determination of Flakiness Index and Elongation Index of Course Aggregates.

Reference : IS : 2386 ( Part I) – 1963, IS: 383-1970, IS : 460-1962

Theory : Particle shape and surface texture influence the properties of freshly mixed concrete more than the properties of hardened concrete. Rough-textured, angular, and elongated particles require more water to produce workable concrete than smooth, rounded compact aggregate. Consequently, the cement content must also be increased to maintain the water-cement ratio. Generally, flat and elongated particles are avoided or are limited to about 15 % by weight of the total aggregate.

Apparatus :
The metal gauge shall be of the pattern shown in Fig. 10.1 & 10.2, Balance.

Procedure :
1. Sample - A quantity of aggregate shall be taken sufficient to provide the minimum number of 200 pieces of any fraction to be tested.

2. Sieving - The sample shall be sieved in accordance with the method described in with the sieves specified in Table 3.18.

3. Separation of Flaky material- Each fraction shall be gauged in turn for thickness on a metal gauge of the pattern shown in Fig. 10.1, or in bulk on sieves having elongated slots. The width of the slot used in the gauge or sieve shall be of the dimensions specified in co1umn 3 of Table 3.18 for the appropriate size of material.

4. Weighing of Flaky Material - The total amount passing the gauge shall be weighed to an accuracy of at least 0.1 percent of the weight of the test sample.

5. The flakiness index is the total weight of the material passing the various thickness gauges or sieves, expressed as a percentage of the total weight of the sample gauged.

6. Sieving - The sample shall be sieved in accordance with the method described in with the sieves specified in Table 3.18.

7. Separation of Elongated Material- Each fraction shall be gauged individually for length on a metal length gauge of the pattern shown in Fig. 10.2. The gauge length used shall be that specified in co1 4 of Table 3.18 for the appropriate size of material.

8. Weighing of Elongated Material - The total amount retained by the length gauge shall be weighed to an accuracy of at least 0.1 percent of the weight of the test sample.

9. The elongation index is the total weight of the material retained on the various length gauges, expressed as a percentage of the total weight of the sample gauged.

Figure :

                                                               figure 10.1

                                                               figure 10.2

Observation :
1. Total weight of course aggregate. . . . . . . g (Flakiness Index)

2. Total weight of course aggregate. . . . . . . g (Elongation Index)

Calculation :

Conclusion / Result :
i) The flakiness index of a given sample of fine aggregate is ………. %
ii) The elongation index of a given sample of fine aggregate is ……..%

Limits :
The combined FI+EI permissible as per IS 383 for construction work is 40%.

Gradation of Coarse Aggregates

Objective : To determination of particle size distribution of coarse aggregates by sieving or
screening.

Reference : IS : 2386 ( Part I) – 1963, IS: 383-1970, IS : 460-1962

Theory :
Grading refers to the determination of the particle-size distribution for aggregate. Grading limits and
maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements, workability, pumpability, and durability of concrete. In general, if the water-cement ratio is chosen correctly, a wide range in grading can be used without a major effect on strength. When gap-graded aggregate are specified, certain particle sizes of aggregate are omitted from the size continuum. Gap-graded aggregate are used to obtain uniform textures in exposed aggregate concrete. Close control of mix proportions is necessary to avoid segregation.

Apparatus :
Test Sieves conforming to IS : 460-1962 Specification of 80 mm, 40 mm, 20 mm, 10 mm, 4.75 mm, Balance, Gauging Trowel, Stop Watch, etc.

Procedure :
1. The sample shall be brought to an air-dry condition before weighing and sieving. This may be achieved either by drying at room temperature or by heating at a temperature of 100‖ to 110°C. The air-dry sample shall be weighed and sieved successively on the appropriate sieves starting with the largest. Care shall be taken to ensure that the sieves are clean before use.

2. Each sieve shall be shaken separately over a clean tray until not more than a trace passes, but in any case for a period of not less than two minutes. The shaking shall be done with a varied motion, backward sand forwards, left to right, circular clockwise and anti-clockwise, and with frequent jarring, so that the material is kept moving over the sieve surface in frequently changing directions.

3. Material shall not be forced through the sieve by hand pressure. Lumps of fine material, if present, may be broken by gentle pressure with fingers against the side of the sieve.

4. On completion of sieving, the material retained on each sieve, together with any material cleaned from the mesh, shall be weighed.

Observation :

Conclusion / Result :
The results may be observed with the below table

Determination of Specific Gravity of Coarse Aggregate

Objective : To determine specific gravity of a given sample of course aggregate.

Reference : IS : 2386 ( Part III ) - 1963

Apparatus :
A wire basket of not more than 6-3 mm mesh, A stout watertight container in which the basket may be freely suspended, well-ventilated oven, Taping rod, An airtight container of capacity similar to that of the basket, etc.

Figure : 

Procedure :
1. A sample of not less than 2000 g of the aggregate shall be thoroughly washed to remove finer particles and dust, drained and then placed in the wire basket and immersed in distilled water at a temperature between 22°C to 32°C with a cover of at least 5 cm of water above the top of the basket.

2. Immediately. after immersion the entrapped air shall be removed from the sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per second. The basket and aggregate shall remain completely immersed during the operation and for a period of 24 ± l/2 hours afterwards.

3. The basket and the sample shall then be jolted and weighed in water at a temperature of 22°C to 32°C (weight A1).

4. The basket and the aggregate shall then be removed from the water and allowed to drain for a few minutes, after which the, aggregate shall be gently emptied from the basket on to one of the dry clothes, and the empty basket shall be returned to the water and weighed in water ( weight A2 ).

5. The aggregate placed on the dry cloth shall be gently surface dried with the cloth, transferring it to the second dry cloth when the first will remove no further moisture. The aggregate shall then be weighed (weight B).

6. The aggregate shall then be placed in the oven in the shallow tray, at a temperature of 100 to 110°C and maintained at this temperature for 24 ± l/2 hours. It shall then be removed from the oven, cooled in the airtight container and weighed (weight C).

7. Calculations— Specific gravity, apparent specific gravity and water &sorption shall be calculated as follows:

A = Weight of saturated aggregate in water = (A1-A2)
B = Weight of the saturated surface - dry aggregate in air
C = Weight of oven dried aggregate in air
A1 = Weight of aggregate and basket in water
A2 = Weight of empty basket in water

Conclusion / Result :
i) The Specific Gravity of a given sample of course aggregate is found to be …….

ii) The Water Absorption of a given sample of course aggregate is found to be ……. %

Determination of Specific Gravity of Fine Aggregate

Objective : To determine specific gravity of a given sample of fine aggregate.


Reference :  IS : 2386 ( Part III ) - 1963

Apparatus : Pycnometer, A 1 000-ml measuring cylinder, well-ventilated oven, Taping rod, Filter papers and funnel, etc.

Figure :

Procedure :

1. A sample of about 500 g shall be placed in the tray and covered with distilled water at a temperature of 22 to 32°C. Soon after immersion, air entrapped in or bubbles on the surface of the aggregate shall be removed by gentle agitation with a rod. The sample shall remain immersed for 24 ± l/2 hours.

2. The water shall then be carefully drained from the sample, by decantation through a filter paper, any material retained being return& to the sample. The fine aggregate including any solid matter retained on the filter paper shall be exposed to a gentle current of warm air to evaporate surface moisture and the material just attains a ‗free-running‘ condition. The saturated and surface-dry sample shall be weighed (weight A).

3. The aggregate shall then be placed in the pycnometer which shall be filled with distilled water. Any trapped air shall be eliminated by rotating the pycnometer on its side, the hole in the apex of the cone being covered with a finger. The pycnometer shall be dried on the outside and weighed (weight B).

4. The contents of the pycnometer shall be emptied into the tray, care being taken to ensure that all the aggregate is transferred. The pycnometer shall be refilled with distilled water to the same level as

before, dried on the outside and weighed (weight C).

5. The water shall then be carefully drained from the sample by decantation through a filter paper and

any material retained returned to the sample. The sample shall be placed in the oven in the tray at a

temperature of 100 to 110°C for 24 f l/2 hours, during which period it shall be stirred occasionally to

facilitate drying. It shall be cooled in the air-tight container and weighed (weight D).

6. Calculations— Specific gravity, apparent specific gravity and water &sorption shall be calculated as follows:

A = weight in g of saturated surface - dry sample,

B = weight in g of pycnometer or gas jar containing sample and filled with distilled water,

C = weight in g of pycnometer or gas jar filled with distilled water only, and

D = weight in g of oven - dried sample.

Conclusion / Result : 

i) The Specific Gravity of a given sample of fine aggregate is found to be …….

ii) The Water Absorption of a given sample of fine aggregate is found to be ……. %

Determination of Silt Content in Fine Aggregate

Objective : To determine silt content in a given sample of fine aggregate by sedimentation
method.

Reference : IS : 2386 ( Part II ) - 1963

Theory :
This is a gravimetric method for determining the clay, fine silt and fine dust, which includes particles up to 20 micron. Differences in the nature and density of materials or in the temperature at the time of testing may vary the separation point.

Apparatus :
A watertight screw-topped glass jar of dimensions similar to a 1-kg fruit preserving jar, A device for rotating the jar about its long axis, with this axis horizontal, at a speed of 80 ± 20 rev/min, A sedimentation pipette, A 1000-ml measuring cylinder, scale, well-ventilated oven, Taping rod etc.

Chemical :
A solution containing 8 g of sodium oxalate per liter of distilled water shall be taken. For use, this stock solution is diluted with distilled water to one tenth (that is 100 ml diluted with distilled water to one liter).

Figure: 

Procedure :

1. Approximately 300 g of the sample in the air-dry condition, passing the 4.75-mm IS Sieve, shall be weighed and placed in the screw-topped glass jar, together with 300 ml of the diluted sodium oxalate solution. The rubber washer and cap shall be fixed, care being taken to ensure water tightness.

2. The jar shall then be rotated about its long axis, with this axis horizontal, at a speed of 80 ± 20

rev/min for a period of 15 minutes.

3. At the end of 15 minutes, the suspension shall be poured into the 1 000-ml measuring cylinder and

the residue washed by gentle swirling and decantation of successive 150-ml portions of sodium

oxalate solution, the washings being added to the cylinder until the volume is made up to 1000 ml.

4. The suspension in the measuring cylinder shall be thoroughly mixed by inversion and the tube and

contents immediately placed in position under the pipette.

5. The pipette A shall then be gently lowered until the tip touches the surface of the liquid, and then

lowered a further 10 cm into the liquid.

6. Three minutes after placing the tube in position, the pipette A and the bore of tap B shall be filled by opening B and applying gentle suction at C.

7. A small surplus may be drawn up into the bulb between tap B and tube C, but this shall be allowed to run away and any solid matter shall be washed out with distilled water from E.

8. The pipette shall then be removed from the measuring cylinder and its contents run into a weighed

container, any adherent solids being washed into the container by distilled water from E through the

tap B.

9. The contents of the container shall be dried at 100 to 110°C to constant weight, cooled and weighed.

10. Calculations— The proportion of fine silt and clay or fine dust shall then be calculated from the

following formula:

W = weight in g of the original sample,

W = weight in g of the dried residue,

V = volume in ml of the pipette, and

0.8 = weight in g of sodium oxalate in one litre of the diluted solution

Conclusion / Result :

The clay, fine silt and fine dust content of given sample of fine aggregate is found to be ……. %

Limits :

As per IS 383 and CPWD permissible amount of silt in sand is 3% by mass and 8% by volume respectively.

Bulking of Sand

Determination of Bulking of Fine Aggregate

Objective : To determine bulking of a given sample of fine aggregate.

Reference : IS : 2386 ( Part III ) - 1963

Theory :

Free moisture forms a film around each particle. This film of moisture exerts what is known as surface tension which keeps the neighbouring particles away from it. Similarly, the force exerted by surface tension keeps every particle away from each other. Therefore, no point contact is possible between the particles. This causes bulking of the volume. It is interesting to note that the bulking increases with the increase in moisture content upto a certain limit and beyond that the further increase in the moisture content results in the decrease in the volume and at a moisture content representing saturation point, the fine aggregate shows no bulking.

Apparatus : Measuring jar, Taping rod etc.

Procedure :

1. Put sufficient quantity of the sand loosely into a container. Level off the top of the sand and pushing a steel rule vertically down through the sand at the middle to the bottom, measure the height. Suppose this is h1 cm.

2. Empty the sand out of the container into another container where none of it will be lost. Half fill the first container with water. Put back about half the sand and rod it with a steel rod, about 6 mm in diameter, so that its volume is reduced to a minimum. Then add the remainder of the sand and rod it in the same way.

3. The percentage of bulking of the sand due to moisture shall be calculated from the formula:

 

                                                                                                   

Conclusion / Result : Bulking of a given sample of fine aggregate is found to be ……. %                        

Gradation of fine aggregates

Sieve analysis of fine aggregates

Object - This method covers the procedure for the determination of particle size distribution of fine, coarse and all-in-aggregates by sieving or screening.

Reference - IS : 2386 ( Part I) – 1963, IS: 383-1970, IS : 460-1962.

Apparatus - Sieves of the sizes given in Table I, conforming to IS : 460-1962 Specification for Test Sieves ( Revised) shall be used.  

Theory : This is the name given to the operation of dividing a sample of aggregate into various fractions each consisting of particles of the same size. The sieve analysis is conducted to determine the particle size distribution in a sample of aggregate, which we call gradation. Many a time, fine aggregates are designated as coarse sand, medium sand and fine sand.

These classifications do not give any precise meaning. What the supplier terms as fine sand may be really medium or even coarse sand. To avoid this ambiguity fineness modulus could be used as a yard stick to indicate the fineness of sand. The following limits may be taken as guidance: Fine sand : Fineness Modulus : 2.2 - 2.6, Medium sand : F.M. : 2.6 - 2.9, Coarse sand : F.M. : 2.9 - 3.2. Sand having a fineness modulus more than 3.2 will be unsuitable for making satisfactory concrete.

Apparatus : Test Sieves conforming to IS : 460-1962 Specification of 4.75 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron, 150 micron, Balance.

Procedure :

1. The sample shall be brought to an air-dry condition before weighing and sieving. The air-dry sample shall be weighed and sieved successively on the appropriate sieves starting with the largest. Care shall be taken to ensure that the sieves are clean before use.

2. The shaking shall be done with a varied motion, backward sand forwards, left to right, circular clockwise and anti-clockwise, and with frequent jarring, so that the material is kept moving over the sieve surface in frequently changing directions.

3. Material shall not be forced through the sieve by hand pressure. Lumps of fine material, if present, may be broken by gentle pressure with fingers against the side of the sieve.

4. Light brushing with a fine camel hair brush may be used on the 150-micron and 75-micron IS Sieves to prevent aggregation of powder and blinding of apertures. 

5. On completion of sieving, the material retained on each sieve, together with any material cleaned from the mesh, shall be weighed. 

      Observation :

Calculation : Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 4.75 mm to 150 micron and dividing this sum by arbitrary number 100.

     Finess Modulus, FM = 

Conclusion / Result :

i) Fineness modulus of a given sample of fine aggregate is …….. that indicate Coarse sand/ Medium sand/ Fine sand.

ii) The given sample of fine aggregate is belong to Grading Zones I / II / III / IV 

Following Links are for your references: Sieve analysis and fineness modulus of fine aggregates