TESTING OF AGGREGATES

CONTENT

SL NO	TYPES OF TESTS
1	AGGREGATE IMPACT VALUE TEST.
2	LOS ANGLES ABRASION VALUE TEST
3	AGGREGATE CRUSHING VALUE TEST
4	FLAKINESS & ELONGATION INDEX TEST( SHAPE TEST )
5	SOUNDNESS TEST
6	SPECIFIC GRAVITY AND WATER ABSORPTION TEST
7	TEN PERCENT FINES VALUE
8	BULKAGE & SILT CONTENT OF FINE AGGREGATE
9	DELETERIOUS CONTENT OF AGGREGATES
I	DETERMINATION OF CLAY LUMPS
II	DETERMINATION OF CLAY, FINE SILT AND FINE DUST
III	DETERMINATION OF LIGHT-WEIGHT PIECES

1.AGGREGATE IMPACT VALUE TEST.

( IS : 2386 – PART – 4 )

INTRODUCTION:

Toughness is the property of a material to resist impact. Due to traffic loads, the road stones are subjected to the pounding action or impact and there is possibility of stones breaking into smaller pieces. The road stones should therefore be tough enough to resist fracture under impact. A test designed to evaluate the toughness of stones i.e., the resistance of the fracture under repeated impacts may be called an impact test for road stones.

 Object:

 To determine the toughness of road stone materials by Impact test.

 Apparatus:

 a) Impact testing machine: The machine consists of a metal base with a plane lower surface supported well on a firm floor, without rocking. A detachable cylindrical steel cup of internal diameter 102mm and depth 50mm is rigidly fastened centrally to the base plate. A metal hammer of weight between 13.5 and 14.0 kg having the lower end cylindrical in shape, 100mm in diameter and 50mm long, with 2mm chamfer at the lower edge is capable of sliding freely between vertical guides, and fall concentric over the cup.

 There is an arrangement for raising the hammer and allowing it to fall freely between vertical guides from a height of 380mm on the test sample in the cup, the height of fall being adjustable up to 5mm. A key is provided for supporting the hammer while fastening or removing the cup.

       

b) Measure: A cylindrical metal measure having internal diameter 75mm and depth 50mm for measuring aggregates.

c) Tamping rod: A straight metal tamping rod of circular cross section, 10mm in diameter and 230mm long, rounded at one end.

d) Sieve: IS sieve of sizes 12.5mm, 10mm, and 2.36mm for sieving the aggregates.

 e) Balance: A balance of capacity not less than 500 gm to weigh accurate up to 0.1 gm.

f) Oven: A thermostatically controlled drying oven capable of maintaining constant temperature between 1000C to1100C.

 Procedure:

The test sample consists of aggregates passing 12.5mm sieve and retained on 10mm sieve and dried in an oven for four hours at a temperature 1000C to 1100C and cooled. Test aggregates are filled up to about one-third full in the cylindrical measure and tamped 25 times with rounded end of the tamping rod. Further quantity of aggregates is then added up to two-third full in the cylinder and 25 stocks of the tamping rod are given. The measure is now filled with the aggregates to over flow, tamped 25 times. The surplus aggregates are struck off using the tamping rod as straight edge. The net weight of the aggregates in the measure is determined to the nearest gram and this weight of the aggregates is used for carrying out duplicate test on the same material. The impact machine is placed with its bottom plate flat on the floor so that the hammer guide columns are vertical. The cup is fixed firmly in position on the base of the machine and the whole of the test sample from the cylindrical measure is transferred to the cup and compacted by tamping with 25 strokes.

The hammer is raised until its lower face is 380mm above the upper surface of the aggregates in the cup, and allowed to fall freely on the aggregates. The test sample is subjected to a total 15 such blows, each being delivered at an interval of not less than one second. The crushed aggregate is then removed from the cup and the whole of it sieved on the 2.36mm sieve until no further significant amount passes. The fraction passing the sieve is weighed accurate to 0.1gm. The fraction retained on the sieve is also weighed and if the total weight of the fractions passing and retained on the sieve is added it should not be less the original weight of the specimen by more than one gram, if the total weight is less than the original by over one gram the results should be discarded and a fresh test made.

 Calculations:

 The aggregate impact value is expressed as the percentage of the fines formed in terms of the total weight of the sample.

100 W2

Aggregate Impact Value =  -------------

    W1

 Where,           W1 = Original weight of the sample.

W2 = Weight of fraction passing 2.36mm IS sieve.

 Results:

The mean of the three results is reported as the AIV(Aggregate Impact Value) of the specimen to the nearest whole number.

 Limits:

 

     < 10%                    Exceptionally strong.

10 – 20%                   Strong.

20 – 30%                   Satisfactory for road surfacing.

     > 35%                    Weak for road surfacing.

 

2. LOS ANGLES ABRASION VALUE TEST.

( IS : 2386 – PART – 4 )

INTRODUCTION:

 Due to the movement of traffic, the road stones used in the surfacing course are subjected to wearing action at the top. Resistance to wear or hardness is hence an essential property for road aggregates, especially when used in wearing course. Thus road stones should be hard enough to resist the abrasion due to the traffic. When fast moving traffic fitted with pneumatic tyres move on the road, the soil particles present between the wheel and road surface causes abrasion on the road stone. Steel tyres of animal drawn vehicles, which rub against the stones, can cause considerable abrasion of the stones on the road surface.

 Hence in order to test the suitability of road stones to resist the abrading action due to traffic.

 Object:

 To determine the aggregates abrasion test by Los Angles Abrasion method.

 Apparatus:

  

a)Los Angles Abrasion Machine: The Los Angles Machine consists of a hollow steel cylinder, closed at both ends, having an inside diameter 700mm and an inside length of 500mm, mounted on stub shafts about which it rotates on a horizontal axis, and rotating arrangement for speed of 30 to 33 revolutions per minute. An opening is provided in the cylinder for the introduction of the test sample. A removable cover of the opening is provided in such a way that when closed and fixed by bolts and nuts, it is dust-tight and the interior surface is perfectly cylindrical. A removable steel shelf projecting radially 88mm in to the cylinder and extending to the full length of it, is mounted on the interior surface of the cylinder rigidly, parallel to the axis. The shelf is fixed at a distance of 1250mm from the opening, measured along the circumference in the direction of rotation.

 Abrasion charge, consisting of cast iron spheres approximately 48mm in diameter and 390 to 445gm in weight are used.

 b) Balance -10 kg capacity – sensitivity 0.1 gm.

 c) Test Sieve – 1.70 mm IS sieve.

 d) Oven.

 Procedure:

Clean aggregates dried in an oven at 105 – 1100C to constant weight, confirming to any one of the grading A, to G, is used for test. The grading or gradings used in the test should be nearest to the grading to be used in the construction. Aggregates weighing 5 kg for gradings A, B, C or D and 10 kg for gradings E, F or G may be taken as test specimen and placed in the cylinder. The abrasion charge is also chosen, depending on the grading of the aggregate and is placed in the cylinder of the machine. The cover is then fixed dust-tight. The machine is rotated at a speed of 30 to 33 revolutions per minute.

 The machine is rotated for 500 revolutions for gradings A, B, C and D, for gradings E, F and G, it shall be rotated for 1000 revolutions. The machine should be balanced and driven in such a way as to maintain uniform peripheral speed.

 After the desired number of revolutions, the machine is stopped and the material is discharged from the machine taking care to take out entire stone dust. Using a sieve of size 1.70mm IS sieve, the material is first separated into two parts and the finer portion is taken out and sieved further on a 1.70mm IS sieve. The portion of material coarser than 1.70mm size is washed and dried in an oven at 105 – 1100C to constant weight and weighed correct to one gram.

Calculations:

The difference between the original and final weights of the sample is expressed as a percentage of the original weight of the sample is reported as the percentage wears.

 

 (W1 – W2)

Los Angles Abrasion Value =        --------------   x 100

     W1

 Where,           W1 = Original weight of the sample.

W2 = Weight of aggregate retained on 1.70mm IS sieve.

(W1 – W2) = Los in weight due to wear.

Results:

 The result of the Los Angles Abrasion is expressed as a percentage wear and the average

value of three tests.

  Limits:

Los Angles Abrasion for road aggregates = Maximum 40%.

Types of Grading and Abrasion charges:

 

 

3.AGGREGATE CRUSHING VALUE TEST.

( IS : 2386 – PART – 4 )

INTRODUCTION:

The principal mechanical properties required in stones are (i) satisfactory resistance to crushing under the roller during construction and (ii) adequate resistance to surface abrasion under traffic.

Aggregates used in road construction, should be strong enough to resist crushing under traffic wheel loads. If the aggregates are weak, the stability of the pavement structure is likely to be adversely affected. The strength of coarse aggregates is assessed by aggregates crushing test. The aggregate crushing value provides a relative measure of resistance to crushing under a gradually applied compressive load. To achieve a high quality of pavement, aggregate possessing low aggregate crushing value should be preferred.

Object:

To determine the aggregate crushing value by compressive testing machine.

Apparatus:

a) Steel cylinder with open ends, and internal diameter 152mm, square base plate, plunger having a piston of diameter 150mm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder.

b) Cylindrical measure having internal diameter of 115mm and height 180mm.

c) Steel tamping rod with one rounded end, having a diameter of 16mm and length 450 to 600mm.

d) Balance of capacity 3 kg with accuracy up to 1gm.

e) Compressive testing machine capable of applying load of 40 tonnes, at a uniform rate of loading of 4 tonnes per minute.

 Procedure:

The aggregate passing 12.5mm IS sieve and retained on 10mm IS sieve is selected for standard test. The aggregate should be in surface dry condition before testing. The aggregate may be dried by heating at a temperature 1000C to 1100C for a period of 4 hours and is tested after being cooled to room temperature.

The cylindrical measure is filled by the test sample of aggregate in three layers of approximately equal depth, each layer being tamped 25 times by the rounded end of the tamping rod. After the third layer is tamped, using the tamping rod as a straight edge levels off the aggregate at the top of the cylindrical measure. About 6.5kg of aggregate is required for preparing two test samples. The test sample thus taken is then weighed. The same weight of the sample is taken in the repeat test.

The cylinder of the test apparatus is placed in position on the base plate; one third of the test sample is placed in this cylinder and tamped 25 times by the tamping rod. Similarly,the other two parts of the test specimen are added, each layer being subjected to 25 blows. The total depth of the material in the cylinder after tamping shall however be 100mm. The surface of the aggregates is leveled and the plunger inserted so that it rests on this surface in level position. The cylinder with the test sample and the plunger in position is placed on compression testing machine. Load is then applied through the plunger at a uniform rate of 4 tonnes per minute until the total load is 40 tonnes, and then the load is released. Aggregates including the crushed portion are removed from the cylinder and sieved on a 2.36mm IS sieve. The material, which passes this sieve, is collected.

The above crushing test is repeated on second sample of the same weight in accordance with above test procedure. Thus two tests are made for the same specimen for taking an average value.

 Calculation:

The aggregate crushing value is defined, as a ratio of the weight of fines passing the specified IS sieve to the total weight of the sample expressed as a percentage.

 

  100 W2

Aggregate crushing value = ----------

    W1

 Where,          W1 = Total weight of dry sample.

W2 = Weight of the portion of crushed material passing 2.36mm IS sieve.

 Results:

The mean of the crushing value obtained in the two tests is reported as the aggregate crushing value.

Limits:

The aggregate crushing value for cement concrete pavement shall not exceed 30%.

The aggregate crushing value for wearing surfaces shall not exceed 45%.

 

4. FLAKINESS & ELONGATION INDEX TEST( SHAPE TEST ).

( IS : 2386 – PART – 1 )

INTRODUCTION:

The particle shape of aggregates is determined by the percentages of flaky and elongated particles contained in it. For base course and construction of bituminous and cement concrete types, the presence of flaky and elongated particles are considered undesirable as they may cause inherent weakness with possibilities of breaking down under heavy loads. The angularity number i.e., flaky and elongation has considerable importance in the gradation requirements of various types of mixes such as bituminous concrete, cement concrete and soil aggregate mixes.

 Object:

To determine the flakiness and elongation of the aggregates by standard flakiness gauge and elongation gauges.

 Apparatus:

a) Flakiness gauge (Thickness gauge): The Flakiness index of aggregates is the percentages by weight of particles whose least dimension is less than three-fifths (0.6) of their mean dimension. The test is not applicable to sizes smaller than 6.3mm. The apparatus consists of a standard thickness gauge of IS sieve sizes 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3mm and a balance to weigh the samples.

  

b) Elongation gauge (Length gauge): The elongation index of aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than one and four fifth times (1.8) their mean dimension. The elongation test is not applicable to sizes smaller than 6.3mm. The apparatus consists of a standard length gauge of IS sieve sizes 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3mm.

   

Procedure:

a) Flakiness Index: The sample is sieved with the sieves mentioned in above. A minimum of 200 pieces of each fraction to be tested is taken and weighed. In order to separate flaky materials, each fraction is then gauged for thickness on a thickness gauge.

 The amount of flaky material passing the gauge is weighed to an accuracy of at least 0.1

percent of the test sample.

 Calculation:

 In order to calculate the flakiness index of the entire sample of aggregates first the weight of each fraction of aggregate passing and retained on the specified set of sieves is noted (X1, X2, X3… etc). Each of the particle from this fraction of aggregate is tried to be passed through the slot of the specified thickness of the thickness gauge are found and weighed (x1, x2, x3… etc). Then the flakiness index is the total weight of the flaky material passing the various thickness gauges expressed as a percentage of the total weight of the sample gauged.

 

(x1 + x2 + x3 + … )

Flakiness Index = -----------------------------  X 100

           (X1 + X2 + X3 + … )

b) Elongation Index: The sample is sieved through the IS sieves specified as above. A minimum of 200 pieces of each fraction is taken and weighed. In order to separate elongated material, each fraction is then gauged individually for length in a length gauge.

The pieces of aggregates from each fraction tested which could not pass through the specified gauge length with its long side are elongated particles and are collected separately to find the total weight of aggregates retained on the length gauge from each fraction. The total amount of elongated material retained by the length gauge is weighed to an accuracy of at least 0.1 percent of the weight of the sample.

 Calculation:

In order to calculate the Elongation index of the entire sample of aggregates first the weight of each fraction of aggregate passing and retained on the specified set of sieves is noted (Y1, Y2, Y3… etc). Each piece of these are tried to be passed through the specified length of the gauge length with its longest side and those elongated pieces which do not pass the gauge are separated and weighed (y1, y2, y3… ). Then 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.

 

(y1 + y2 + y3 +… )

Elongation Index = ---------------------------      X 100

(Y1 + Y2 + Y3 + … )

Combined Flakiness & Elongation Index: To determine this combined proportion, the flaky stone from a representative sample should first be separated out. Flakiness index is weight of flaky stone metal divided by weight of stone sample. Only the elongated particle is separated out from the remaining (non flaky) stone metal. Elongation index is weight of elongated particles divided by total non-flaky particles. The value of flakiness index and elongation index so found are added up.

 Limits:

(i) Flakiness Index for Bituminous and Non-bituminous Mixes = Max. 15%

(ii) Elongation Index for Bituminous and Non-bituminous mixes = Max. 15%

(iii) Combined Flakiness and Elongation Index for Bituminous and Non-bituminous mixes = Max.30%

(iv) Flakiness Index for Concrete mixes = Max.35%

  

5.SOUNDNESS TEST.

( IS : 2386 – PART – 5 )

INTRODUCTION:

This test is intended to study the resistance of aggregates to weathering action.

 In order to quicken the effect of weathering due to alternate wet-dry and or freeze-thaw cycles in the laboratory, the resistance to disintegration of aggregate is determined by soaking the specimen in saturated solution of sodium sulphate or magnesium sulphate.

 Object:

 Determination of the soundness of aggregates.

 Apparatus:

The apparatus required for the test are containers for aggregates, sieves (63, 50, 40, 31.5, 20, 16, 10, 8, 4.75 and 4mm), balance of capacity 5kg to weight accurate to at least 0.1g and oven to maintain 1050C to 1100C.

  

Procedure:

Saturated solution of Sodium sulphate (the anhydrous Na2SO4 or the crystalline Na2SO4 10H2O) is prepared in water at a temperature of 250 to 300C. The solution is maintained at a temperature of 270C+/-20C and stirred at frequent intervals, until it is used. At the time of using the solution should have a specific gravity of not less than 1.151 and not more than 1.171, and discolored solution should not be used. It may be necessary to use not less than 420g of anhydrous salt or 1300g of the crystalline decahydrate salt per liter of water.

Alternatively saturated solution of Magnesium sulphate may be prepared by dissolving either anhydrous (MgSO4) or crystalline (MgSO47H2O) magnesium sulphate. At the time of using, the solution should have a specific gravity of not less than 1.295 and not more than 1.308. Not less than 400g of the anhydrous salt or 1600g of the crystalline heptahydrate may be used per liter of water.

The specimen of coarse aggregate for the test may be prepared after removing the fraction finer than 4.75mm IS sieve. The sample should be of such a size that it would yield not less than the following amounts of the different sizes, which should be available in amount of 5 percent or more.

 (i)         20mm to 10mm                                 - 1000 g

10mm to 4.75mm                              -  300 g

 

consisting of 20 to 12.5mm            – 67%

         12.5 to 10mm               – 33%

 

(ii)        40mm to 20mm                                 - 1500 g

 

consisting of 40 to 25mm               – 67%

25 to 20mm               – 33%

 

(iii)       63mm to 40mm                                 - 3000 g

 

consisting of 63 to 50mm               – 50%

50 to 40mm               – 50%

 (iv)       80mm and large sizes by

20mm spread in sieve size,            - 3000 g

each fraction

The sample of coarse aggregate should be thoroughly washed and dried to a constant weight at 1050 to 1100C and is separated to different size ranges, as given above, by sieving. The proper weight of the sample for each fraction is weighed and placed in separate containers for the test. In the case of fraction coarser than 20mm, the particles are also counted. The samples are immersed in the prepared solution of sodium sulphate or magnesium sulphate for 16 to 18 hours in such a manner that the solution covers them to a depth of at least 15mm. The containers are kept covered to reduce evaporation and during the period of immersion, the temperature of the solution is maintained at 270 +/- 10C.

After the immersion period, the aggregates are removed from the solution, drained for about 15 minutes, and placed in the drying oven maintained at a temperature of 1050 t o 1100C. The samples are dried to a constant weight at this temperature by checking the weights after 4 hours up to 18 hours. When the successive weights differ by less than 1 g, it may be considered that constant weight has been attained and then it may be allowed to cool to room temperature. Then the aggregates are again immersed in the prepared solution, for the next cycle of immersion and drying. The number of cycles of alternate immersion and drying are minimum 5 for road aggregates.

 After completion of the final cycle, the sample is cooled washed free from the sulphat.

This may be determined when there is no more reaction of the wash water with barium chloride (i.e., when there is no white precipitation when barium chloride is added to wash water, it can be said that there is no sulphate with wash water). Each fraction of the sample is then dried to constant temperature of 1050 to 1100C and weighed. Coarse aggregate fractions are sieved by IS sieves of sizes indicated below:

 Size of aggregate                                         Sieve size used to determine loss

 

63 to 40 mm                                                                          31.5 mm

40 to 20 mm                                                                          16.0 mm

20 to 10 mm                                                                           8.0 mm

10 to 4.75 mm                                                                        4.0 mm

 

Each fraction of aggregate is examined visually to see if there is any evidence of excessive splitting, crumbling or disintegration of the grains. A combined sieve analysis of all the materials subjected to the above test cycles, may also be carried out to note the variation from the original grain size distribution of the sample.

 

Limits:

Soundness of aggregates: Loss with Sodium Sulphate                      – 5 cycles Max.12%.

 Loss with Magnesium Sulphate                                                               – 5 cycles Max.18%.

6.SPECIFIC GRAVITY AND WATER ABSORPTION TEST.

( IS : 2386 – PART – 3 )

INTRODUCTION:

The specific gravity of an aggregate is considered to be a measure of strength or quality of the material. The specific gravity test helps in the identification of stone.

Water absorption gives an idea of strength of aggregate. Aggregates having more water absorption are more porous in nature and are generally considered unsuitable unless they are found to be acceptable based on strength, impact and hardness tests.

 Object:

To determine the specific gravity and water absorption of aggregates by perforated basket.

 Apparatus:

 a) A wire basket of not more than 6.3mm mesh or a perforated container of convenient size with thin wire hangers for suspending it from the balance.

 b) A thermostatically controlled oven to maintain temperature of 1000 to 1100C.

 c) A container for filling water and suspending the basket.

 d) An airtight container of capacity similar to that of the basket.

 e) A balance of capacity about 5 kg, to weigh accurate to 0.5 g, and of such a type and shape as to permit weighing of the sample container when suspended in water.

 f) A shallow tray and two dry absorbent clothes, each not less than 750 X 450 mm.

 

Procedure:

About 2 kg of the aggregate sample is washed thoroughly to remove fines, drained and then placed in the wire basket and immersed in distilled water at a temperature between 220 to 320C with a cover of at least 50mm of water above the top of the basket.

Immediately after immersion the entrapped air is removed from the sample by lifting the basket containing it 25mm 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 the aggregate should remain completely immersed in water for a period of 24 +/- 0.5 hours afterwards.

 The basket and the sample are then weighed while suspended in water at a temperature of 220 to 320C. In case it is necessary to transfer the basket and the sample to a different tank for weighing, they should be jolted 25 times as described above in the new tank to remove air before weighing. This weight is noted while suspended in water W1 g. The basket and the aggregate are then removed from water and allowed to drain for a few minutes, after which the aggregates are transferred to one of the dry absorbent clothes.

The empty basket is then returned to the tank of water, jolted 25 times and weight in water W2 g.

The aggregates placed on the absorbent clothes are surface dried till no further moisture could be removed by this cloth. Then the aggregates are transferred to the second dry cloth spread in a single layer, covered and allowed to dry for at least 10 minutes until the aggregates are completely surface dry. 10 to 60 minutes drying may be needed. The aggregates should not be exposed to the atmosphere, direct sunlight or any other source of heat while surface drying. A gentle current of unheated air may be used during the first ten minutes to accelerate the drying of aggregate surface. The surface dried aggregate is then weighed W3 g. The aggregate is placed in a shallow tray and kept in an oven maintained at a temperature of 1100C for 24 hours. It is then removed from the oven,

cooled in an airtight container and weighed W4 g. At least two tests should be carried out, but not concurrently.

 Calculations:

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

Weight of basket suspended in water                                                                              = W2 g

Weight of saturated aggregate in water = (W1-W2)                                                       = Ws g.

Weight of saturated surface dry aggregate in air                                                           = W4 g

Weight of water equal to the volume of the aggregate                                                 = (W3-Ws) g

 

        Dry weight of aggregate

(i) Specific gravity = -------------------------------------------

 Weight of equal volume of water

 

      W4                                    W4

= -------------     =  ----------------------

    W3 - Ws                      W3 – (W1 – W2)

 

Dry weight of aggregate

(ii)Apparent Sp.gr. = -----------------------------------------------------------------------------------------                   

(Weight of equal volume of water excluding air voids in aggregates)

 

W4                                W4

= -----------------            =  -----------------------

      W4 – Ws      W4 – (W1 – W2)

 

(iii) Water absorption           = percent by weight of water absorbed in terms oven dried weight

   of aggregates.

(W3 – W4) 100

= ----------------------------

 W4

 

Limits:           

The specific gravity of aggregates ranges from              2.5 to 3.0

The water absorption of aggregates ranges from          0.1 to 2.0 %.

 

7. TEN PERCENT FINES VALUE.

( BS : 812 – PART – 111 )

INTRODUCTION:

The ‘Ten percent fines’ value is a measure of resistance of the aggregates to the crushing.

 Object:

 To determine the ten percent value of aggregates by crushing machine apparatus.

Apparatus:

a) Steel cylinder with open ends, and internal diameter 152mm, square base plate, plunger having a piston of diameter 150mm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder.

b) Cylindrical measure having internal diameter of 115mm and height 180mm.

c) Steel tamping rod with one rounded end, having a diameter of 16mm and length 450 to

600mm.

d) Balance of capacity 3 kg with accuracy up to 1gm.

 e) Compressive testing machine capable of applying load of 40 tonnes, at a uniform rate of loading of 4 tonnes per minute.

 

Procedure:

 The aggregate passing 14mm IS sieve and retained on 10mm IS sieve is selected for test.

The aggregate should be in surface-dry condition before testing. The aggregate may be dried by heating at a temperature 1000C to 1100C for a period of 4 hours and is tested after being cooled to room temperature.

The cylindrical measure is filled by the test sample of aggregate in three layers of approximately equal depth, each layer being tamped 25 times. The same sample poured in to the cylinder with three equal layers, each layer being tamped 25 times. The test sample in the cylinder with the plunger in position is placed in the compression-testing machine. The load is applied at a uniform rate so as to cause a total penetration of the plunger of about 20mm for normal crushed aggregates in 10 minutes. But for rounded or partially rounded aggregates, the load required to cause a total penetration of 15mm is applied where as for honeycombed aggregate like expanded shale or slag that for a total penetration of 24mm is applied in 10 minutes. After the maximum specified penetration is reached, the load is released and the aggregate from the cylinder is sieved on a 2.36mm IS sieve. The fines’ passing this sieve is weighed and is expressed as a percentage by

weight of the test sample. This percentage normally falls in the range of 7.5 to 12.5; but if it does not fall in this range, the test is repeated with necessary adjustment of the load.

 Two tests are carried out at the load ‘X tonnes’, which give the percentage fines between 7.5 to 12.5 and let the mean of the percent fines be ‘Y’ for calculating the load required for ten percent fines.

 

   14 X

Load for 10 percent fines =            ------------

  (Y + 4)

Results:

 The 10 percent fines value of Granular Sub base material is should be more than 50 KN.

 

8. BULKAGE & SILT CONTENT OF FINE AGGREGATE.

( IS : 2386 – PART – 3 )

 INTRODUCTION:

Sand brought on to a building site or other works may contain an amount of moisture, which will cause it, when loosely filled into a container, to occupy a large volume than it would occupy if dry. If the sand is measured by loose volume, it is necessary in such a case to increase the measured volume of the sand, in order that the amount of sand put into the concrete may be the amount intended for the nominal mix used (based on dry sand). It will be necessary to increase the volume of sand by the ‘percentage’ bulking.

The correction to be made is only a rough approximation because the system of measurement by loose volume is a rough method at the best, but a correction of the right order can easily be determined and should be applied in order to keep the concrete uniform.

 Object:

This method of test covers the field method for determining the necessary adjustment for the bulking & silt content of fine aggregate.

 Apparatus:

250ml measuring cylinder, tray and water cane etc.

Procedure:

In a 250ml-measuring cylinder, pour the damp sand (consolidated by shaking) until it reached the 200ml mark. Then fill the cylinder with water and stir the sand well (the water shall be sufficient to submerge the sand completely). It will be seen that the sand surface is now below its original level. Suppose the surface is at the mark ‘Y’ml the percentage of bulking of the sand due to moisture shall be calculated from the formula.

 

                           200

Percentage bulking               =        ( --------   - 1) X 100

                              Y

  

            (X – Y)

Silt content                            =       ---------- X 100

                                       Y

 

Where,           X = the level of top surface of material i.e., sand + sedimentation of silt.

Y = the level of top surface of sand layer.

Results: Report the percentage bulking of the sand to the nearest whole number.

Limits: Bulkage and silt content is allow maximum 10%

 

 9. DELETERIOUS CONTENT OF AGGREGATES.

( IS : 2386 – PART – 2 )

 

I. DETERMINATION OF CLAY LUMPS:

 Apparatus:

1) Balance – sensitive to 0.001 g, 2) Containers – size and shape that will permit the spreading of the sample on the bottom in a thin layer, 3) Sieves – conforming to IS : 460- 1962.

Sampling:

Samples shall be obtained by quartering or by the use of a sampler, from a representative sample selected from the material to be tested. They shall be handled in such a manner as to avoid breaking up clay lumps, which may be present. Samples shall be dried to constant weight at a temperature not exceeding 1100C.

Samples of fine aggregate shall consist of particles coarser than 1.18 mm IS sieve and shall weigh not less than 100 g.

Samples of coarse aggregate shall be separated into different sizes using 4.75mm, 10mm, 20mm and 40mm IS sieves. The weight of the sample for different sizes shall be not less than those indicated below:

 

Size of Particles Making Up the Samples (mm)	Weight of Sample Min.(g)
4.75 to 10	1000
10 to 20	2000
20 to 40	3000
Over 40	5000

 

 

 

In the case of mixtures of fine and coarse aggregates, the material shall be separated into two sizes on 4.75mm IS sieve, and the samples of fine and coarse aggregates shall be prepared as described above.

 

Procedure:

 

The sample shall be spread in a thin layer on the bottom of the container and examined for clay lumps. Any particles, which can be broken into finely divided particles with the fingers, shall be classified as clay lumps. After all discernible clay lumps have been broken, the residue from the clay lumps shall be removed by the use of sieves indicated below:

 

Size of Particles Making up the Sample	Size of Sieve for Sieving Residue of Clay Lumps
Fine aggregate (retained on 1.18mm IS sieve)	850 - micron
4.75 to 10 mm	2.36 mm
10 mm to 20 mm	4.75 mm
20 mm to 40 mm	4.75 mm
Over 40 mm	4.75 mm

 

Calculations:

 

The percentage of clay lumps shall be calculated to the nearest 0.1 percent in accordance with the following formula:

 

                               (W – R)

L = ------------- X 100

                      W

 

Where,           L = percentage of clay lumps.

W = weight of sample.

R = weight of sample after removal of clay lumps.

 

II. DETERMINATION OF CLAY, FINE SILT AND FINE DUST.

 Apparatus:

1) A watertight screw-topped glass jar of dimensions similar to a 1-kg fruit-preserving jar,

2) A device for rotating the jar about its axis, with this axis horizontal, at a speed of 80 +/- 20 rev/min,

3) A sedimentation pipette of the Andreason type of approximately 25 ml capacity. This consists mainly of a pipette fitted at the top with a two way tap and held rigidly in a clamp which can be raised or lowered as required, and which is fitted with a scale from which the changes in height of the pipette can be read,

 4) A 1000 ml measuring cylinder,

 5) A scale or balance of capacity not less than 10 kg, readable and accurate to one gram,

 6) A scale or balance of capacity not less than 250 g, readable and accurate to 0.001 g,

7) A well ventilated oven, thermostatically controlled, to maintain a temperature of 100 to 1100C.

Chemicals:

 A solution containing 8 g of sodium oxalate per litre 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 litre).

Test sample:

The sample for test shall be prepared from the main sample taking particular care that the test sample contains a correct proportion of the finer material. The amount of sample taken for test shall be in accordance with below table.

 

Maximum size present in substantial proportions (mm)	Approximate weight of sample for test (kg)
63 to 25	6
20 to 12.5	1
10 to 6.3	0.5
4.75 or smaller	0.3

  All in aggregates shall be separated into fine and coarse fractions by sieving on a 4.75 mm IS sieve and the two samples so obtained shall be tested separately.

Procedure:

Method for fine aggregate: 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. 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. At the end of 15 minutes, the suspension shall be poured into the 1000 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. The determination shall be completed as described below.

Method for coarse aggregate: The weighed sample shall be placed in a suitable container, covered with a measured volume of sodium oxalate solution (0.8 g per litre),agitated vigorously to remove all adherent fine material and the liquid suspension transferred to the 1000 ml measuring cylinder. This process shall be repeated as necessary until all clayey material has been transferred to the cylinder. The volume shall be made up to 1000 ml with sodium oxalate solution and the determination completed as described below.

The suspension in the measuring cylinder shall be thoroughly mixed by inversion and the tube and contents immediately placed in position under the pipette. The pipette shall then be gently lowered until the tip touches the surface of the liquid, and then lowered a further 10 cm into the liquid. Three minutes after placing the tube in position, the pipette and the bore of tap shall be filled by opening and applying gentle suction. A small surplus may be drawn up into the bulb between tap and tube, but this shall be allowed to run away and any solid matter shall be washed out with distilled water from top end. 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 top end. The contents of the container shall be dried at 100 to 1100C to constant weight, cooled and weighed.

Calculations: The proportion of fine silt and clay or fine dust shall then be calculated from the following formula:

 

         100           1000W2

Percentage of clay and fine silt or fine dust =  ------   x  ( ----------         -  0.8 )

W1             V

 

Where,                     W1 = weight in g of the original sample.

W2 = weight in g of the dried residue.

V = volume in ml of the pipette

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

  

III. DETERMINATION OF LIGHT-WEIGHT PIECES.

 Apparatus:

1) Balances – for weighing fine aggregates, a balance having a capacity of not less than 500 g, sensitive to at least 0.1 g; for weighing coarse aggregates, a balance having a capacity of not less than 5000 g, sensitive to at least 1 g.

 2) Containers – containers suitable for drying the aggregate sample, and containers suitable for holding the heavy liquid during the sink-float separation.

 3) Skimmer – a piece of 300-micron sieve cloth of suitable size and shape for separating the floating pieces from the heavy liquid.

 4) Hot-plate or oven.

 Heavy liquid: The heavy liquid shall consist of a mixture of carbon tetrachloride, and 1, 1, 2, 2-tetrabromoethane, bromoform, and monobromobenzene, or bromoform and benzene, in such proportions that the desired specific gravity will be obtained.

Bromotrichloromethane may be used as a heavy liquid having a specific gravity of 2.00.

The specific gravity shall be maintained within +/- 0.01 of the specified value at all times during the test.

The approximate volumes of materials to be combined to produce a mixture of the desired specific gravity may be computed from the following specific gravitY of the different liquids:

 

Liquid	Specific gravity
1,1,2,2-tetrabromoethane	2.97
Benzene	0.88
Bromoform	2.88
Carbon tetrachloride	1.58
Monobromobenzene	1.49

  For determining coal and lignite, the heavy liquid used shall have a specific gravity of

2.00 +/- 0.01.

Test Sample: The minimum size of test sample shall be as follows:

 

Maximum size of aggregate (mm)	Minimum weight of sample (grms)
6.3 (fine aggregate)	200
20	3000
40	5000
80	10000

 

 Procedure:

 1) Fine aggregate: Allow the dried sample of fine aggregate to cool to room temperature and then sieve over a 300-micron IS sieve until less than one percent of the retained material passes the sieve in one minute of continuous sieving. Weigh the material coarser than the 300-micron IS sieve to the nearest 0.1 g; then introduce it into the heavy liquid in a suitable container, the volume of liquid being at least three times the absolute volume of the aggregate. Pour the liquid off into a second container; passing it through the skimmer and taking care that only the floating pieces are poured off with the liquid and that none of the sand is decanted onto the skimmer. Return to the first container the liquid that has been collected in the second container and, after further agitation of the sample by stirring, repeat the decanting process just described until the sample is free of floating

pieces. Wash the decanted pieces contained on the skimmer in carbon tetrachloride, until the heavy liquid is removed, and then dry. The pieces will dry very quickly, but may be placed in an oven at 1050C for a few minutes if desired. Brush the dry decanted pieces from the skimmer onto the balance pan and determine the weight to the nearest 0.1 g.

2) Coarse aggregate: Allow the dried sample of coarse aggregate to cool to room temperature and sieve over a 4.75 mm IS sieve. Weigh the material coarser than the 4.75 mm IS sieve to the nearest 1 g; then introduce it into the heavy liquid in a suitable container, the volume of the liquid being at least three times the absolute volume of the aggregate. Using the skimmer, remove the pieces that rise to the surface, and save them.

Repeatedly agitate the remaining pieces and remove the floating pieces until no additional pieces rise to the surface. Wash the decanted pieces in carbon tetrachloride until all of the heavy liquid is removed, and allow to dry. Determine the weight of the decanted pieces to the nearest 1-gram.

Calculations: Calculate the percentage of lightweight pieces as follows:

For fine aggregate:

 

W1

L =       ----- X 100

W2

 For coarse aggregate:

W1

L =       ----- X 100

W3

 Where,           L = percentage of lightweight pieces.

W1 = dry weight in g, of decanted pieces.

W2 = dry weight in g, of portion of sample coarser than 300-micron IS sieve.

W3 = dry weight in g, of portion of sample coarser than 4.75 mm IS sieve.

 IV. DETERMINATION OF SOFT PARTICLES.

 Apparatus: The apparatus shall consist of a brass rod, having a Rockwell hardness of 65 RHB to 75 RHB. A brass rod of about 1.6mm diameter and of proper hardness inserted into the wood shaft of an ordinary lead pencil is a convient tool for field or laboratory use.

 Test Sample: Aggregates for the test shall consist of material from which the sizes finer than the 10mm IS sieve have been removed. The sample tested shall be of such size that it will yield not less than the following amount of the different sizes, which shall be available in amounts of 10 percent or more:

 

Maximum size of aggregate (mm)	Minimum weight of sample (grms)
10 to 12.5	200
12.5 to 20	600
20 to 25	1500
25 to 40	4500
40 to 50	12000

 Procedure:

Each particle of aggregate under test shall be scratched with the brass rod with a small amount of pressure (about 1 kg). Particles are considered to be soft if during the scratching process, a groove is made in them without deposition of metal from the brass rod or if separate particles are detached from the rock mass.

Calculations: The report shall include the following information.

a) Weight and number of particles of each size of each sample tested with the brass rod.

b) Weight and number of particles of each size of each sample classified as soft in the test.

c) Percentage of test sample classified as soft by weight and by number of particles.

d) Weighed average percentage of soft particles calculated from percentage in item (c) and based     on the grading of sample of aggregate received for testing.