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| Test on bitumen pdf |
Tests on Bitumen
Introduction
Various tests on bitumen are:
- Penetration Test
- Ductility Test
- Softening Point Test
- Viscosity Test
- Flash and fire point Test
- Specific gravity Test
The following are ome of the important tests.
Penetration test for bitumen
1.Objective
To determine the hardness of the bitumen materials by measuring in tenths of millimetre for which a standard needle will penetrate vertically under specified conditions of standard load, time and temperature.
2.Apparatus
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| penetration test of bitumen pdf |
It consists of a container, needle, water bath and penetrometer which allow the needle to penetrate without appreciable friction. It vields results in tenths of a millimetre. Electrically operated penetrometer can also be utilised.
3.Sample material
The bitumen is softened to 90 °C, thoroughly mixed to make it homogenous and free from air bubbles. Water sample is poured into a container to a depth of at least 10mm more than the expected penetration. Then the container is cooled to atmospheric temperature between 15° C and 30°C. Then it is placed at room temperature for about two hours.
4.Test procedure
Sample container is placed in the transfer tray and is placed under the needle. The total weight of the assembly should be 100gm. The needle is now arranged to make contact with the sample surface. Zero reading of the penetration dial is taken before releasing the needle. The needle is released for 5 seconds and the final reading is taken on the dial. At least three measurements are taken on sample by testing at distances of not less than 10mm apart. After each test e needle is wiped and carefully dried. The sample container is also transferred the water bath before the next testing is done so as to maintain a constand temperature of 25°C. The test is repeated on samples in other containers.
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5.Results
Depth of penetration is registered in tenths of millimetres. penetration test of bitumen is used for determining its mean value of these consistent measurements is reported as the penetration value. The bitumen grade is specified in terms of penetration value. For example, 90 grade bitumen means that the penetration value of the bitumen is in the range of 90 at standard test conditions. The penetration test is applied almost exclusively to bitumen.
6.penetration test of bitumen conclusion
The penetratioh values of various types of bitumen used in pavement construction in this country ranges between 20 and 225. Depending upon road and traffic characteristics 35, 65 or 90 grade bitumen are more commonly used. In hot climate lower penetration grade bitumen like 35 bitumen are preferred.
Ductility test for bitumen
1.Objective
To determine the ductility expressed in centimetres to which a standard briquette of bitumen is stretched before the thread breaks.
2.Apparatus
(a) Briquette mould (Brass model)
- Length 75 mm
- Distance between clips 30 mm
- Width at mouth of clips 20 mm
- Cross section at minimum width 10 x 10 mm
- Thickness throughout 10 mm
Both ends of the mould called clips possess holes to grip the fixed and movable ends.
(b) Ductility machine
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| ductility test of bitumen pdf |
The machine has a pulling device. It is pulled apart at uniform rate of (5042.5)mm per minute.
3.Procedure
- Bitumen sample melted to 75°C to 100°C (until it is fluid)
- It is strained through IS sieve 30, poured in the mould assembly and placed on a brass plate.
- A solution of glycerine and dextrin is applied at all surfaces of the mould exposed to bitumen
- About 30-40 minutes after a sample is poured into the mould,the plate assembly along with the sample is placed in water bath maintained at 27°C for 30 minutes. The sample and mould assembly is removed from water bath and excess bitumen materials cut off by levelling the surface using a hot knife. After trimming the specimen, the mould assembly containing sample is replaced in water bath maintained at 27°C for 85 to 95 minutes.
- The sides of the mould are removed and clips carefully hooked on to machine. The pointer is set to read zero. The machine pulls apart the clips horizontally. During the operation, the sample is to be immersed in water atleast to a depth of 25mm. Record the distance at which thread breaks
4.ductility test of bitumen conclusion
Ductility is the distance in centimetres at which thread breaks. The experiment is repeated and mean value is taken as ductility.
5.Allowable variation
- Repeatability - 10% of the mean
- Reproductibility-20% of the mean
Viscosity test
Definition
It is a measure of resistance to flow due to internal friction.
1.Objective
To determine the time taken for 60ml of bituminous material to flow from a cup through a specified orifice under standard condition of test and at specified temperature.
Apparatus
(a) Main parts
Viscometer (10 mm orifice)
- Cup
- Water bath
- stirrer (m)
- Valve
- Sleeves
- Receiver and thermometers
4.Procedure
Viscosity is generally determined by efflux Viscometers. Water in the bath is heated to specified temperature and is maintained out through the test. The sample material is heated to 20°c above specified test temperature and allowed to cool The test material is continuously stirred. When the material reaches a slightly above the test temperature, the same is poured into a tar cup, until the levelling peg on the valve rod is just immersed .In the graduated receiver (cylinder) 20ml of mineral oil, or one percent (by weight) soft soap solution is poured. The receiver is placed under the orifice. Valve is opened (for 5 minutes) when the standard material reaches the specified testing temperature. The Stop watch is started when the cylinder records 20ml.Time is recorded for flow up to the mark of 80ml. (i.e. 60 ml test sample to flow through orifice).
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| viscosity test of bitumen pdf |
5.Result
Time in seconds for 60 ml of sample material to flow through the orifice is the viscosity. Two viscosity values of repeat tests on the same sample should not vary by more than +4 percent from the mean value.
Softening point test
1.Definition
It is the temperature at which the substance attains a particular degree of softening under specified condition of test.
2.Objective
To determine the softening point of the bitumen through ring and ball test.
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3.Apparatus
(a) Steel balls
- Numbers - two
- Diameter 9.5mm
- Weight - 3.5 gms.
(b) Brass rings
- Numbers - two
- Depth - 6.4 mm
- Inside dia at bottom - 15.9 mm
- Inside dia at top - 17.5 mm
- Out side dia - 20.6 mm
(c) Bath (a heat resistant glass container)
- Dia - 85 mm
- Depth - 120 mm
- Bath liquid water (for materials with softening point below 80°C)
- Glycerine (for materials having softening point above 80°C)
(d) Stirrer
A mechanical stirrer to ensure uniform heat distribution all times through out the bath
4.Procedure
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| softening point of bitumen pdf |
Sample material is heated to 75 to 100°C above the approximate softening point until it becomes completely fluid. Pour the sample into heated rings placed on metal plate coated with glycerine and dextrin to avoid sticking of the bitumen to metal plate. Cool the rings for 30 minutes. Excess bitumen is trimmed and rings are placed on the support. The temperature of distilled water is kept at 5°C.This temperature is maintained for 15 min and after which the balls are placed in position .Temperature of water is raised at uniform rate of 5°C per min with controlled heating, until the bitumen softens and touches the bottom plate by sinking of balls. A minimum of two observations are made.
5.Result
The temperature at the instant, when each of the balls with sample touches the bottom plate of support is recorded as softening point.
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