Key Tests for Aggrgates

Key Tests for Aggregates

The following Key tests to be done on coarse aggregates before using to make the quality concrete are as follows:

* Aggregates Crushing Value Test

* Aggregates Impact Value Test

* Aggregates Abrasion Value Test

* Water Absorption Test

Aggregates Crushing Value Test:

Object

This method of test covers the procedure for determining the

Aggregate crushing value of coarse aggregate.

Why to be done

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

The apparatus for the standard test shall consist of the

Following:

a) A 15-cm diameter open-ended steel cylinder, with plunger and base-plate of the general form. The surfaces in contact with the aggregate shall be machined and case-hardened .

b) A straight metal tamping rod of circular cross-section 16 mm in diameter and 45 to 60 cm long, rounded at one end.

c) A balance of capacity 3 kg, readable and accurate to one gram.

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

e) A compression testing machine capable of applying a load of 46 tonnes and which can be operated to give a uniform rate of loading so that the maximum load is reached in 10 minutes. The machine may be used with or without a spherical seating.

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Scope This test is used to determine the resistance of coarse aggregate to impact in a rotating cylinder containing metallic spheres. This test is known as the Los Angeles Abrasion Test. Sample - Using the Riffle Box obtain a representative sample of the aggregate. -Dirty or coated aggregate shall be washed, dried to constant mass at 110 +/- 5^0 C, and cooled to room temperature before preparing ...

f) 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

Height 18.0 cm

Preparation of test sample

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

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.

The quantity of aggregate shall be such that the depth of material in the cylinder, after tamping shall be 10 cm.

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.

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.

Test Procedure

The cylinder of the test apparatus shall be put in position on the base-plate and the test sample added in thirds, each third being subjected to 25 strokes from the tamping rod. The surface of the aggregate shall be carefully leveled and the plunger inserted so that it rests horizontally on this surface, care being taken to ensure that the plunger does not jam in the cylinder.

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.

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The total load shall be 40 tonnes.

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

In all of these operations, care shall be taken to avoid loss of the fines.

Two tests shall be made.

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

where

B = weight of fraction passing the appropriate sieve, and

A = weight of surface-dry sample.

Reporting of Results

The mean of the two results shall be reported the nearest whole number as the ‘aggregate crushing value’ of the size of material tested, which shall be stated.

NOTE 1

Aggregate larger than 12.5 mm – In general, the larger sizes of aggregate will give a higher aggregate crushing value, but the relationship between the values obtained with different sizes will vary from one aggregate to another. Particular care shall be taken with larger sizes of aggregate to ensure that the plunger does not jam in the cylinder. However, for such aggregate, a 7.5cm diameter cylinder may be used, and this has been found to give slightly higher results than the standard cylinder, sothat the errors are compensating.

NOTE 2

Aggregate smaller than 10 mm – In general, the smaller sizes of aggregate will give a lower aggregate crushing value, but the relationship between the values obtained with different sizes will vary from one aggregate to another.

For testing aggregate smaller than 10 mm:

* The form and dimensions of the 7.5-cm cylinder shall be as shown and the surfaces shall be as for the standard cylinder.

* The tamping rod shall be 8 mm in diameter and 30 cm long, rounded

at one end.

* The balance shall be of capacity 500 g, readable and accurate

to 0.2 g.

* The compression testing machine shall be capable of applying a

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To compare the hardness between mild steel, carbon steel through Vickers Hardness Test. 2) To compare the hardness between High Quality Carbon Steel and ASSAB steel through Rockwell Hardness Test. 3) To compare the hardness between carbon steel and mild steel through Brinell Hardness Test. 4) To study the differences between mild steel and carbon steel upon Charpy Impact Test. Introduction: ...

load of 10 tonnes uniformly in 10 minutes.

* The metal measure shall be 6 cm in diameter and 9 cm in height.

* The depth of material in the 7.5-cm cylinder shall be 5 cm after

tamping.

* The total load applied in 10 minutes shall be 10 tonnes.

Aggregates Crushing Testing Material

Aggregate Impact Test

Objective:

To determine Impact value of given stone aggregate sample.

Apparatus:

The apparatus consists of an impact testing machine, a cylindrical measure, tamping rod, IS sieves, balance and oven.

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 10.2 cm and depth 5cm 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, 10cm in diameter and 5 cm long, with 2 mm chamfer at the lower edge is capable of sliding freely between vertical guide 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 38 cm on the test sample in the cup, the height of fall being adjustable upto 0.5 cm. A key is provided for supporting the hammer while fastening or removing the cup.

Measure a cylindrical metal measure having internal diameter 7.5 cm and depth 5 cm for measuring aggregates.

Tamping rod: A straight metal tamping rod of circular cross section, 1 cm in diameter and 23 cm long, rounded at one end.

Sieve: IS sieve of sizes 12.5 mm, 10 mm and 2. 36 mm for sieving the aggregates.

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

Oven: A thermostatically controlled drying oven capable of maintaining constant temperature between 100°C and 100°C.

Procedure:

The test sample consists of aggregates passing 12.5 m sieve and retained on 10 mm sieve and dried in an oven for four hours at a temperature 100°C to 110 C 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 about two-third full in the cylinder and 25 strokes 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 fiat 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.

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The hammer is raised until its lower face is 38 cm 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 of 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 2.36 mm sieve until no further significant amount passes. The fraction passing the sieve is weighed accurate to 0.1g. 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 than the original weight of the specimen by more than one gram; if the total weight is less than the original by over one gram, If the result should be-discarded and a fresh test made.

Calculation:

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

Let the original weight of the oven dry sample be WI g and the weight of fraction passing 2.36 mm

IS sieve be W2 g.

Aggregate impact value = 100W2/W1 percent.

This is recorded correct to the first decimal place.

Results:

The mean of the two results is reported as the aggregate impact value of the specimen to the nearest Whole number.

Aggregate impact value is to classify the stones in respect of their toughness property as indicated Below:

< 10% =exceptionally strong.

10-30% = satisfactory for road surfacing.

10-20% = strong.

> 35% = Weak for road surfacing.

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Impact Testing Machine

Aggregates Abrasion Value Test

Objective:

Test for Abrasion of Coarse Aggregates by the Use of Los Angeles Machine.

Apparatus

The apparatus shall consist of the following: Los Angeles machine, The Los Angeles abrasion testing machine, conforming in all its essential characteristics to the design shall be used. The 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. The opening shall be closed dust-tight with a removable cover bolted in place. The cover shall be so designed as to maintain the cylindrical contour of the interior surface unless the shelf is so located that the charge will not fall on the cover, or come in contact with it during the test. A removable steel shelf, projecting radials 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 position of the shelf shall be such that the distance from the shelf to the opening, measured along the circumference of the cylinder in the direction of rotation, shall be not less than 1 250 mm.

NOTE1:

The use of the shelf of wear-resistant steel, rectangular in cross-section and mounted independently of the cover, is preferred. However, a shelf consisting of a section of rolled angle, properly mounted on the inside of the cover plate, may be used, and provided the direction of rotation is such that the charge will be caught. On the outside face of the angle. _

NOTE 2:

Shaft bearing will be mounted on concrete piers or other rigid supports.

NOTE 2:

Suggested horse power for motor is not less than one.

Abrasive Charge:

The abrasive charge shall consist of cast iron spheres or steel spheres approximately 48 mm in. diameter and each weighing between 390 and 445 g.

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Test Sample :

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 grading. The grading used shall be those most nearly representing the aggregate furnished for the work.

NOTE:

It is recognized that different specification limits may be required for grading E, F and G than for A, B, C and D. It is urged that investigations be conducted to determine the relationship, if any, which exists between results for these coarse grading using the 10000 g samples and the finer ones using the 5000 g samples.

Procedure:

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 grading A, B, C and D, the machine shall be rotated for 500 revolutions; for grading E, F and G, it shall be rotated for 1 000 revolutions. 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. 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.70mm IS Sieve. The material coarser than the 1.70mm 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.

NOTE:

Attention is called to the fact that valuable information concerning the uniformity of the sample under. test may be obtained by determining the loss after 100 revolutions. When this determination is made, care should be taken to avoid loss of any part of the sample; the entire sample, including the dust of abrasion, shall be returned to the testing machine for the completion of the test.

Reporting of Result:

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

Abrasion Value Test Apparatus

Water Absorption Test

Object:

This test covers the procedures for determining the specific gravity, apparent specific gravity and water absorption of aggregates.

Note:

Three main methods are specified for use according to whether size of the aggregate is large than 10 mm (Method I) between 40 mm and 10 mm (Method I or II may be used); or smaller than 10 mm (Method III).

Note:

The water absorption test will not always be reproducible with aggregate of high porosity.

Apparatus:

The apparatus shall consist of the following: A balance or scale of capacity not less than 3 kg, readable and accurate to 0.5 g and of such a type and shape as to permit the basket containing the sample to be suspended from the beam and weighed in water. Oven – A well ventilated oven, thermostatically controlled, to maintain a temperature of 100 to 110%. A wire basket of not more than 6-3 mm mesh or a perforated container of convenient size, preferably chromium plated and polished, with wire hangers not thicker than one millimetre for suspending it from the balance. A stout watertight container in which the basket may be freely suspended. Two dry soft absorbent cloths each not less than 75 x 45 cm.

A shallow tray of area not less than 650sq.m. An airtight container of capacity similar to that of the basket. A sample of not less than 2000 g of the aggregate shall be tested.’ Aggregates which have been artificially heated shall not normally be used. If such, material is used the fact shall be stated in the report. Two tests shall be made, and it is recommended that the two samples should not be tested concurrently.

Test Procedure:

The sample 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 and 32°C with a cover of at least 5 cm of water above the top of the basket.

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.

The basket and the sample shall then be jolted and weighed in water at a temperature of 22 to 32% If it is necessary for them to be transferred to a different tank for weighing, they shall be jolted 25 times as described above in the new tank before weighing ( weight A, ).

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, jolted 25 times and weighed in water ( weight 4 ).

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. It shall then be spread out not more than one stone deep on the second cloth, and lest exposed to the atmosphere away from direct sunlight or any other source of heat for not less than 10 minutes, or until it appears to be completely surface dry (which with some aggregates may take an hour or more).

The aggregate shall be turned over at least once during this period and a gentle current of unheated air may be used after the first ten minutes to accelerate the drying of difficult aggregates. The aggregate shall then be weighed (weight B).

The aggregate shall then be placed in the oven in the shallow tray, at a temperature of I00 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).

Calculation:

Specific gravity, apparent specific gravity and water absorption shall be calculated as follows:

Specific gravity= C/ (B-A)

Apparent specific gravity = C/(C-A)

Water absorption ( percent of dry weight) =100(B-C)/C

where

A= The weight in g of the saturated aggregates in water.(A1-A2)

B =The weight in g of the saturated surface dry aggregate in air, and

C = the weight in g of oven dried aggregate in air.

Reporting of Result:

The individual and mean results shall be reported. The size of the aggregate tested shall be stated, and whether it has been artificially heated.

Method2: Aggregates between 40mm and 10mm.

Apparatus:

The apparatus shall consist of the following: A balance or scale of capacity not less than 3 kg, readable and accurate to 0.5 g, and of such a type as to permit the weighing of the vessel containing the aggregate and water.

Oven: A well ventilated oven thermostatically controlled to maintain a temperature of 100 to 110°C.

Glass Vessel or Jar : A wide-mouthed glass vessel such as a jar of about 1.5 litres capacity, with. a flat ground lip and a plane ground disc of plate glass to cover it, giving a virtually watertight fit.

Cloths: Two dry soft absorbent cloths, each not less than 75 x 45 cm.

Tray: A shallow tray of area not less than 325sq.m

Container: An airtight container large enough to take the sample.

Sample: A sample of about one kilogram of the aggregate shall be used. Aggregates which have been artificially heated shall not normally be used; if such material is used, the fact shall be stated in the report. Two tests shall be made and it is recommended that the two samples should not be tested concurrently.

Test Procedure:

The sample shall be screened on a I0mm IS sieve, thoroughly washed to remove fine particles of dust, and immersed in distilled water in the glass vessel; it shall remain immersed at a temperature of 22 to 32°C for 24 +/- l/2 hours. soon after immersion and again at the end of the soaking period, air entrapped in or bubbles on the

surface of the aggregate shall be removed by gentle agitation. This may

be achieved by rapid clockwise and anti-clockwise rotation of the vessel

between the operator’s hands.

The vessel shall be overfilled by adding distilled water and the plane ground-glass disc slid over the mouth so as to ensure that no air is trapped in the vessel. The vessel shall be dried on the outside and

weighed ( weight A ).

The vessel shall be emptied and the aggregate allowed to drain. Refill the vessel with distilled water. Slide the glass disc in position as before. The vessel shall be dried on the outside and weighed

( weight B ).

The difference in the temperature of water in the vessel during the first and second weighings shall not exceed 2°C.

The aggregate shall be placed on a dry cloth and gently surface dried with the cloth, transferring it t a second dry cloth when the first will remove no further moisture. It shall then be spread out not more than one stone deep on the second cloth, and left exposed to the atmosphere away from direct sunlight or any other source of heat for not less than 10 minutes or until it appears to be completely surface dry (which with some aggregates may take an hour or more) The aggregate shall be turned over at least once during this period and a gentle current of unheated air may be used after the first ten minutes to accelerate the difficult aggregates. The aggregate shall then be weighed.

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

Calculation:

Specific gravity, apparent specific gravity and water absorption shall be calculated as follows:

Specific gravity=D/ ((C-(A-B))

Apparent specific gravity =D/ ((D-(A-B))

Water absorption (percent of dry weight) =100(C-D)/D

where

A = weight in g of vessel containing sample and filled with distilled water,

B = weight in g of vessel filled with distilled water only,

C = weight in g of saturated surface-dry sample, and

D = weight in g of oven-dry sample..

Reporting of Results:

The individual and’ main results shall be reported. The grading of aggregate tested shall be stated, and whether

It has been artificially heated.

Method III – Aggregate Smaller Than 10 mm

Apparatus:

The apparatus shall consist of the following: A balance or scale of capacity not less than 3 kg, readable and accurate to 0.5 g, and of such a type as to permit the weighing of the vessel containing the aggregate and water.

Oven: A well ventilated oven, thermostatically controlled, to maintain a temperature of 100 to 110°C.

Vessel: Any form of vessel capable of holding 0.5 to 1 kg of material up to 10 mm in size and capable of being filled with water to a constant volume with an accuracy of f 0.5 ml. Either of the two following vessels is suitable:

1) A glass vessel, referred to later as a pycnometer, of about one litre capacity having a metal conical screw top with a 6-mm diameter hole at its apex. The screw top shall be watertight when it is screwed on to the jar, and, if necessary, a rubber or fibre washer shall be inserted in the joint. If such a washer is used, a mark shall be made on the jar to correspond with a mark on the screw top so that the screw is tightened to the same position every time and the volume contained by the jar is constant throughout the test. A suitable vessel can be made from a 1kg fruit preserving jar in which the glass lid normally used is replaced by a sheet metal cone as shown in

2) A wide-mouthed glass vessel, such as a gas jar, of about 1.25 litres capacity, with a flat ground lip and a plane ground disc of plate glass to cover it, giving a virtually watertight fit.

A means of supplying a current of warm air, such as a hair drier.

A tray of area not less than 325 cm2.

An airtight container large enough to take the sample.

Filter papers and funnel.

Test Procedure:

Using the pycnometer – A sample of about 1 kg for 10 mm to 4.75 mm or 500 g if finer than 4.75 mm, 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. 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 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 shall be stirred at frequent intervals to ensure uniform drying until no free surface moisture can be seen and the material just attains a ‘ free-running ’ condition. Care shall be taken to ensure that this stage is not passed. The saturated and surface-dry sample shall be weighed (weight A).

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 topped up with distilled water to remove any froth from the surface and so that the surface of the water in the hole is flat. The pycnometer shall be dried on the outside and weighed (weight B ).

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).

The difference in the temperature of the water in the pycnometer during the first and second weighings shall not exceed 2°C. 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 ).

.

CaIculation:

specific gravity, apparent specific gravity and water & absorption shall be calculated as follows:

Specific gravity =D/ ((A-(B-C))

Apparent specific gravity =D/((D-(B-C))

Water absorption ( percent of dry weight) = 100 ( A – D )/D

where

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.

Reporting of Results:

The individual and mean results shall be reported and the grading of the aggregate shall be stated.

Water Absorption Test Apparatus