Determination OF Aggregate Impact Value PDF

Preview

Summary

it is about the test that we have done during our course practical...

Description

DETERMINATION OF AGGREGATE IMPACT VALUE

OBJECTIVE: 1. To determine the impact value of road aggregate. 2. To assess the suitability in road construction on basis of impact value.

APPARATUS REQUIRED:

Fig. 1: Balance Balance should be accurate upto 1 g

Fig. 2: Sieves Seives required are 12.5, 10.0 and 2.36 mm

Fig. 3: Impact Testing machine Weight of hammer is 13.5 to 14.0 kg and Height of Fall is 380±5 mm

THEORY: The property of a material to resist impact is known as toughness.Due to movement of vechicles on the road, the aggregate are subjected to impact resulting in their breaking down into smaller pieces. The aggregate should therefore have sufficient toughness to resist their disintegration due to impact. The aggregate impact value is measure of resistance to sudden impact or shock which may differ from its resistance to gradually applied compressive load. 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. 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.

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. Further similar quantity of aggregate shall be added and a further tamping of 25 strokes given. The measure shall finally be filled to overflowing, tamped 25 times and the surplus aggregate struck off, using the tamping rod as a straight edge. 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.

OBSERVATION AND CALCULATION Sample 1 Weight of cylindrical steel cup (w’) = Weight of cup + weight of sample (w) = Weight of sample (W1) = w-w’= Weight of sample passing 2.36mm sieve after test (W2) = Aggregate impact Value ( AIV1 ) = (W2/W1)*100%

Sample 2 Weight of cylindrical steel cup (w’) = Weight of cup + weight of sample (w) = Weight of sample (W1) = w-w’= Weight of sample passing 2.36mm sieve after test (W2) = Aggregate impact Value ( AIV2 ) = (W2/W1)*100% =

INTERPRETATION OF RESULT: Aggregate impact value is used to classify the stones with respect to their toughness property as indicated below: Aggregate impact value

classification

35%

Weak for road surfacing

The indian road standard has recommended the following values of different types of road construction. SN

Types of pavement

Maximum aggregate impact value

1

Bitumenous surface dressing penetration macadam bituminous carpet concrete and cement concrete wearing course

30

2

Bitumen-band macadam, base course

35

3

WBM base course with bitumen surfacing

40

4

Cement concrete base course

45

Hence, Avg(AIV)= ((AIV1)+(AIV2))/2

RESULT: Since the AIV mean value is=

which lies between =

that mean given aggregate is =

DISSCUSSION AND CONCLUSION: Hence, the aggregate used in the lab was =

so that can be used for

PRECAUTION: 1. The test sample should consist of clean aggregate. 2. The aggregate should be weight and sieved carefully.

DETERMINATION OF LOS ANGEL’S ABRASION VALUE

OBJECTIVE: 1. To determine the Los Angel’s Abrasion value. 2. To find out suitability of aggregate for its use in road construction.

APPARATUS REQUIRED:

1. 2. 3. 4.

Los Angel’s Abrassion machine Abrasion Charge Weighing machine Tray

Weighing Machine

THEORY

The Los Angeles (L.A.) Abrasion Test is widely used as an indicator of the relative quality of aggregates. It measures the degradation of standard grading of aggregates when subjected to abrasion and impact in a rotating steel drum with an abrasive charge of steel balls. The drum is fitted with an internal shelf that lifts and drops the charge and sample with each revolution, generating impact forces. After the machine has completed the required rpm, contents are removed and percent loss is measured. The Los Angeles (LA) abrasion method is commonly used for determining the abrasion characteristics and classification of the granular materials used in road and pavement construction. The abrasion resistance of materials can significantly affect the service life of road pavements when exposed to longterm dynamic traffic loads. The LA abrasion method suffers from several drawbacks including the time needed to perform the test, the operational noise and dust and the space required by the machine. The objective of this study was to investigate whether the modified compaction method can be a suitable alternative for determining the LA abrasion value. This study was proposed in consideration of the similarities in the treatment of materials by the LA abrasion method and the modified compaction method. It was considered that the laboratory-modified compaction method closely simulates the abrasion resistance of the unbound granular materials in the base course and sub-base layers of road pavements that experience repetitive dynamic loads. As indicated by the results of tests on nineteen different aggregate samples, a strong correlation exists between the Los Angeles Abrasion Values (LAVs) and the values obtained when implementing the modified compaction method, namely, the Compaction Abrasion Values (CAVs). Abrasion testing determines the relative quality, toughness, and durability of mineral aggregates subjected to impact and abrasion. Values derived from both the Micro Deval and the L.A. Abrasion tests offer information about the performance of aggregate in use. This testing offers insight into how asphalt and concrete aggregates will stand up to wear and tear over time. It’s also a good indicator of changing properties in an aggregate source as part of quality control or quality assurance program.

PROCEDURE:

A sample is prepared by separating into individual size fractions of the required masses. 1.

The sample of specifically sized aggregates and the abrasive charge is placed in the L.A. Abrasion Machine and rotated at 500 rpm.

2.

The sample is removed and washed over a No. 12 (1.70mm) sieve and placed in an oven to dry.

3.

The percent loss or the difference between the original mass and the final mass is calculated.

4.

An L.A. Abrasion loss value of 40 indicates that 40% of the original sample mass passed through the sieve.

OBSERVATION AND CALCULATION: Total weight of sample (W1) = Weight of aggregate retained on 17 mm sieve after test= W2 = Loss weight=W1-W2= LAV=(L/W)*100%

RESULT: Los Angel’s Abrasion test is commonly used to evaluate the hardness of aggregate. The test has more acceptability because the resistance to abrasion and impact is determined simultaneously. Depending upon the numerical values, the suitability of aggregate for different road construction can be judge as per Indian road congress specification below: SN

Type of pavement layer

1

Water bounded macadam, sub base course

Max permissible abrasion value in % 60

2

WBM base course with bitumen surfacing

50

3

Bitumen bound macadam

50

4

WBM surfacing course

40

5

Bitumen surface dressing cement concrete surfacing course

35

6

Bitumenous concrete surface course

30

7

Bitumen penetration macadam

40

DISCUSSION: From the above data and the practical the Los Angel’s Value obtained was= the aggregate can be used to make bituminous penetration macadam.

CONCLUSION: Hence the Los Angel’s Value of sample was determined in laboratory.

which means that

DETERMINATION OF SOFTENING POINT OF BITUMINUOUS MATERIAL

OBJECTIVE: 1. To determine the softening point of bitumen.

APPARATUS REQUIRED: 1. ring and ball test of bitumen

Ring & Ball Apparatus

THEORY:

The softening point shows the temperature at which the bitumen gains a certain degree of softening under the specifications of the test. This test is carried out by using the Ring and Ball apparatus. The softening point helps to determine the temperature up to which bitumen can be heated for different road use applications. The softening point helps in the determination of the temperature beyond which the bitumen is softened beyond a pre-specified softness.Hence, the softening point test of bitumen helps in knowing the maximum temperature to which the given bitumen can be exposed.This is utilized while using bitumen as a binder for road construction. Softening point value gives the temperature at which the bitumen should be heated before using it for pavement construction.If the climatic temperature exceeds the softening point, the bitumen used as binder starts to melt and the pavement becomes sticky. PROCEDURE:



  

The bitumen was heated up to a temperature between 75 – 100 degree celcius above it’s softening point, stirred until it was completely fluid and free from air bubbles and water. The ring previously heated to temperature approximately to that of molten material was placed on the metal plate which was coated with a mixture of equal part of glycerin and dextrin. After cooling for 30 min the material was placed in ring by removing the excess material with a warmed sharp knife. The apparatus was assembled with ring, thermometer and ball guides in position. The bath was filled with distilled water to the height of 50mm above the upper surface of rings. The heat was applied to bath and stirred the liquid so that the temperature rises at uniform rate 5 (+- 0.5) degree celcius per minute.



 

The temperature was increased until the bitumenious material softens and ball sinks through the ring carrying a portion of the material with it. The temperature was noted when steel ball with bitumineous coating touches the bottom plate. The average of two reading to the nearest 0.5 degree celicus were repeated as softening point.

OBSERVATION AND CALCULATION: Ball Temperature at which the ball touches the bottom in degree celcius

1

2

Average=

Softening point of bitumen=

RESULT: The required softeninig point of the given bitumen was found to be

CONCLUSION: Hence, softening point of bituminous material was determined and the softening point was higher so reffered in warm climate.

DISCUSSION: Higher the softening point ensure that they don’t melt at lower temperature so such bitumen are used in warm climate and vice-verca. PRECAUTION: 1. Temperature should be noted carefully. 2. The bulb of thermometer should be at same level as ring.

3. Distilled water or glycerol should be used as heating material....