TEST ON BITUMINOUS MATERIALS

There are a number of tests to assess the properties of bituminous materials. The following tests are usually conducted to evaluate different properties of bituminous materials. They are;

1. Penetration test

2. Ductility test

3. Specific gravity test

4. Flash and Fire point Test

5. Determination of binder content for Asphalt mix

6. Marshall method of Bituminous Mix Design

7. Superpave Gyratory Compactor

8. Dynamic Cone Penetrometer

9. Benkelman Beam Deflection Measurement

10. Softening Point of Bitumen.

PENETRATION OF BITUMINOUS MATERIALS

OBJECTIVES

To examine the consistency of a sample of bitumen by determining the distance in tenths of a millimetre that a standard needle vertically penetrates the bitumen specimen under known conditions of loading, time and temperature.

BACKGROUND

This is the most widely used method of measuring the consistency of a bituminous material at a given temperature. It is a means of classification rather than a measure of quality. (The engineering term consistency is an empirical measure of the resistance offered by a fluid to continuous deformation when it is subjected to shearing stress). The consistency is a function of the chemical constituents of bitumen, viz. the relative proportions of asphaltenes (high molecular weight, responsible for strength and stiffness), resins (responsible for adhesion and ductility) and oils (low molecular weight, responsible for viscosity and fluidity). The type and amount of these constituents are determined by the source petroleum and the method of processing at the refinery.

Penetration is related to viscosity and empirical relationships have been developed for Newtonian materials. If penetration is measured over a range of temperatures, the temperature susceptibility of the bitumen can be established. The consistency of bitumen may be related to temperature changes by the expression

Log P = AT + K . . . (1)

Where P = penetration at temperature T A = temperature susceptibility (or temperature sensitivity) K = constant

A Penetration Index (PI) has been defined for which the temperature susceptibility would assume a value of zero for road bitumen, as given by

PI = . . . (2)

The value of A (and PI) can be derived from penetration measurements at two temperatures, T1 and T2, using the equation

A = log (pen at T1) log (pen at T2) . . . (3a)

T1-T2

Research has shown that, for conventional paving grade bitumens, the Ring-andBall Softening Point temperature is the same as that which would give a penetration of 800 d-mm. This, together with the penetration at 25 oC, can be used to compute A where

log (pen at 25 0C) - log 800 A = . . . (3b)

25 ASTM softening point

The nomograph as given in Figure 1 enables the PI to be deduced approximately from the penetration at 25 oC and the softening point temperature. Typical values of PI are

Bitumen type PI

Blown Bitumen >2

Conventional Paving Bitumen -2 to +2

Temperature Susceptible Bitumen (Tars)

Figure 1. Nomograph for the Penetration Index of bitumen (Whiteoak, 1990)

Draw a line between the softening point (line 'A')and penetration (line 'B') values. The intercept online 'C' is the PI of the bitumen

A

B

C

PROCEDURE

The penetration apparatus (Figure 2) is specified in many standards throughout the world but has always the same basic requirements as ASTM D5.

1. Specimens are prepared in sample containers exactly as specified (ASTM D5-97) and placed in a water bath at the prescribed temperature of test for 1 to 1.5 hours before the test.

2. For normal tests the precisely dimensioned needle, loaded to 100 0.05 g, is brought

to the surface of the specimen at right angles, allowed to penetrate the bitumen for 5 0.1 s, while the temperature of the specimen is maintained at 25 0.1 oC. The penetration is measured in tenths of a millimetre (deci-millimetre, d-mm).

3. Make at least three determinations on the specimen. A clean needle is used for each

determination. In making repeat determinations, start each with the tip of the needle at least 10 mm from the side of the container and at least 10 mm apart.

100g

AsphaltCement(25 C)

Penetrationin units of 0.1 mm

(25 C)AsphaltCement

100g

Start After 5 seconds

Figure 2. Apparatus for the bitumen penetration test

RESULTS

The results are very sensitive to test conditions and bitumen specimen preparation and the requirements of the appropriate standard must be rigidly adhered to. The maximum difference between highest and lowest readings shall be:

Penetration (d-mm) 0-49 50 - 149 150 - 249 250-500

Maximum Difference 2 4 12 20

DISCUSSION

(a) Report the source and type of bitumen. (b) Specify the conditions of the test (temperature, load, time). Note the three separate

readings and quote the penetration as the average to the nearest whole unit. (c) Comment on the difference between the highest and lowest readings and, if sub-

standard, offer an explanation. (d) Compare the average penetration with the manufacturer's quoted range and, if

outside this, offer an explanation. (e) Calculate the PI and comment on the value obtained. (Make sure the penetration and

softening point values are obtained from the same batch of bitumen). (f) Compile and compare results with other groups.

REFERENCES

1. ASTM (1998). ASTM D5-97 Standard test method for penetration of bituminous materials. 1998 Annual Book of ASTM Standards, Volume 04.03, American Society for Testing and Materials, Philadelphia 19103-1187.

2. Whiteoak, D. (1990). Shell Bitumen Handbook. Shell Bitumen UK, London.

DUCTILITY TEST Introduction In the flexible pavement construction where bitumen binders are used, it is of significant importance that the binders form ductile thin films around the aggregates. This serves as a satisfactory binder in improving the physical interlocking of the aggregates. This test is done to determine the ductility of distillation residue of cutback bitumen, blown type bitumen and other bituminous products as per IS: 1208 1978. The ductility of a bituminous material is measured by the distance in cm to which it will elongate before breaking when a standard briquette specimen of the material is pulled apart at a specified speed and a specified temperature. Objective: To determine the ductility of the bituminous material. Apparatus: a) Ductility machine. b) Briquette moulds. c) Knife.

Figure. 3: Briquette mould Procedure: The bitumen sample is melted to a temperature of 75 to 1000C above the approximate softening point until it is fluid. It is strained through 90 micron sieve, poured in the mould assembly and placed on a brass plate, after a solution of glycerin and dextrin is applied at all surfaces of the mould exposed to bitumen. After 30 to 40 minutes, the plate assembly along with the sample is placed in water bath maintained at 270C for 30 minutes. The sample and mould assembly are removed from water bath and levelling the surface using hot knife cuts off excess bitumen material. After trimming the specimen, the mould assembly-containing sample is replaced in water bath maintained at 270C for 85 to 95 minutes. The sides of the mould are now removed and the clips are carefully hooked on the machine without causing any initial strain. The pointer is set to zero, the machine is started and the two clips are pulled apart horizontally at a uniform speed of 50 +/- 2.5mm per minute. While the test is in operation, it is checked whether the sample is immersed in water at depth of at least 10mm. The distance, at which the bitumen thread of each specimen breaks, is recorded (in cm) to report as ductility value. Results: The distance stretched by the moving end of the specimen up to the point of breaking of thread measured in centimeters is recorded as ductility value. Limits: The minimum ductility value of A35 & S35 grade bitumen is 50 cm at 270C. All other grades, the ductility value is 75 cm at 270C.

.

SPECIFIC GRAVITY TEST

Introduction

Specific gravity -- the ratio of the weight in air of a volume of material at 77 F (25 C) to the mass in air of an equal volume of water.Residual pressure equals the pressure in a vacuum container when vacuum is applied

SCOPE

The volumetric properties of HMA are required to be controlled during design and production to produce durable pavements. A test to measure the volume of a mixture with all the air voids removed is needed to measure this durability. The maximum specific gravity (Gmm) of HMA is the ratio of the weight of the loose sample to the weight of an equal volume of water at the standard temperature of 77F (25C)

Gmm is used along with the bulk specific gravity (Gmb) of the compacted mixture to determine air voids (Pa). The Gmm is often used also for determining the percent of compaction in laboratory specimens or during roadway compaction.

The procedure using a vacuum container for plant-produced mixture is the procedure that will be discussed herein. INDOT uses the weighing-in-water procedure with a vacuum container for determining the maximum specific gravity. Other procedures are covered in AASHTO T 209.

SUMMARY OF TESTS

Vacuum Container, capacity of at least 2000 mL, capable of withstanding the full vacuum applied and having a No. 200 (75 m) wire mesh covering the hose opening Vacuum System, capable of subjecting contents to a partial vacuum of 27.5 2.5 mm Hg (3.7 0.3 kPa). Residual Pressure Manometer, capable of measuring the residual pressure down to 30 mm Hg (4.0 kPa)

Thermometer, conforming to the requirements of ASTM E 1 with subdivisions and a maximum scale error of 1F (0.5C)

Figure 4

Maximum Specific Gravity Apparatus

SAMPLE SIZE

The size of the sample shall conform to the following requirements. Samples larger than the capacity of the vacuum container may be tested a portion at a time.

Nominal Maximum Aggregate Size

Minimum Sample Size

1 in. (37.5 mm) 4000 g 1 in. (25.0 mm) 2500 g

3/4 in. (19.0 mm) 2500 g 1/2 in. (12.5 mm) 1500 g 3/8 in. (9.5 mm) 1500 g

#4 (4.75 mm) 1500 g PROCEDURE

1. Separate particles of the sample without fracturing any aggregate until the fine

aggregate particles are not larger than 1/4 in. (6.3 mm) (Figure 2). The sample may be placed in a large pan and warmed in an oven until the sample is workable.

Figure 5

Separating Particles of the Sample

2. Dry the sample to constant weight in an oven at 221 9F (105 5C). (This drying

and curing is combined with any warming needed to separate the sample) 3. Cool the sample to room temperature, place the sample in a tared vacuum container,

and weigh to the nearest 0.1 gram (A) 4. Add sufficient water at a temperature of approximately 77F (25C) to cover the

sample completely (Figure 3)

Figure 6

Covering Sample with Water at 77 F

5. Remove air trapped in the sample by applying gradually increasing vacuum until the

residual pressure manometer reads 27.5 2.5 mm Hg (3.7 0.3 kPa) (Figure 4)

Figure 7

Manometer Residual Pressure

6. Agitate the container and contents during the vacuum period by a mechanical device

(Method A - Figure 5). The container and contents may be agitated manually by vigorously shaking at intervals of about 2 minutes (Method B).

Figure 8

Agitating Vacuum Container

7. After 15 2 minutes, release the vacuum by increasing pressure slowly Weighing-in-

Water 1. Suspend the container and contents in the water bath and determine the weight (C)

after 10 1 min. immersion (Figure 6)

Figure 9

Suspending Container in Water Bath

2. Empty the container immediately following the weighing of the container and sample 3. Suspend the container in water without delay and determine the weight (B) 4. Calculate the theoretical maximum specific gravity to three decimal places (0.000) as

follows:

A

Max. Sp. Gr. =

A (CB)

where:

A = weight of dry sample in air, g B = weight of container in water, g C = weight of container and sample in water, g

Supplemental Procedure

If the pores of the aggregates are not thoroughly sealed with binder film, they may become saturated with water during the application of the vacuum. To determine if this has occurred, drain the water from the sample by decanting through a towel, and break open several large pieces of aggregate. If the broken surfaces indicate wetness, the following procedure should be applied.

Note: This procedure has an insignificant effect on the test results if the mixture contains individual aggregates with water absorptions below 1.5 percent.

1. Spread the sample before an electric fan to remove the surface moisture (Figure 8)

Figure 10

Removing Sample Surface Moisture

2. Break conglomerations of the mixture by hand and intermittently stir the sample

3. Weigh the sample at 15-minute intervals (When the loss in weight (A1) is less than 0.05 percent for this interval, the sample may be considered to be surface dry)

4. Calculate the theoretical maximum specific gravity to three decimal places (0.000) as

follows: Weighing at 77 2F (25.0 1C)

FLASH & FIRE POINT TEST

OBJECTIVE

To determine the Flash & Fire point test of a given bitumen sample

APPARATUS

Cleaveland apparatus

Thermometer-Low Range: -7 to 110 oC, Graduation 0.5 oC

-High Range: 90 to 370 oC, Graduation 2 oC

Figure 11: Cleveland apparatus

PROCEDURE

Note: Bitumen is just sufficient to fill the cup up to the mark given on it.

Flash Point

1) Heat the bitumen between 75 and 100 oC & remove the air bubbles and water by

stirring the sample.

2) Fill the cup with the bitumen to be tested up to the mark & place it on the bath. Fix

the open clip; insert the thermometer of high or low range as per requirement and

also the stirrer, to stir the sample.

3) Light the test flame and supply heat at such a rate that the temperature increase, recorded using a thermometer is neither less than 5oC nor more than 6oC per minute.

4) Note the temperature at which first flash appears when test flame is bought close to

the surface of the material. This temperature is noted as Flash point temperature.

Note: Do not get confused with the bluish halo that sometimes surrounds the test flame with

the true flash.

Fire Point

5) After flash point is obtained, heating should be continued at such a rate that the

increase in temperature recorded by the thermometer is neither less than 5oC nor

more than 6oC per minute.

6) Now light a test flame and adjust it so that it is of the size of a bead 4mm in diameter.

7) Finally note that thermometer at which the application of test flame causes the

material to ignite and burn for at least 5 seconds. This temperature is noted as Fire

point temperature.

RESULTS

Flash point temperature (oC) =

Fire point temperature (oC) =

REFRENCES

(IS: 1205, BS2000-58, 1958, ASTM D36-95, 1995, AASHTO T53-06, 2006)

DETERMINATION OF BINDER CONTENT FOR ASPHALT MIX

OBJECTIVE

To determine the binder content in the asphalt mix by cold solvent extraction

APPARTUS

Binder Centrifuge Extractor

Balance of capacity 500 g and sensitivity 0.01 g

Thermostatically controlled oven with capacity up to 250oC

Beaker for collecting extracted material

Figure 12.1: Binder Centrifuge Extractor Figure 12.2: Precision Balance

PROCEDURE

1) Take a known weight (W1) of representative sample and place it in the bowl of

extraction apparatus.

2) Add benzene to the sample until it is completely submerged. 3) Take a dry filter paper with weight (F1) and place it over the bowl of the extraction

apparatus containing the sample.

4) Clamp the cover of the bowl tightly.

5) Place a beaker under the drainpipe to collect the extract

6) Allow sufficient time (not more than an hour) for the solvent to disintegrate the

sample before running the centrifuge.

7) Run the centrifuge slowly and then gradually increase the speed to a maximum of

3600 rpm.

8) Maintain the same speed till the solvent ceases to flow from the drainpipe.

9) Run the centrifuge until the bitumen and benzene are drained out completely.

10) Stop the machine, remove the cover and add 200ml of benzene to the material in the

extraction bowl and the extraction is done in the same process as described above.

11) Repeat the same process not less than three times till the extraction is clear and not

darker than a light straw colour.

12) Collect the material from the bowl of the extraction machine along with the filter

paper and dry it to constant weight in the oven at a temperature of 105 to 1100C and

cool to room temperature.

13) Weigh the material (W2) and the filter paper (F2) separately to an accuracy of 0.01 g.

RESULTS

W1 (W2 + W3)

Percentage of binder in the total mix = ---------------------- x 100

W1

W1 = Weight of sample taken

W2 = Weight of sample after extraction

W3 = Increased weight of filter paper (F2 F1)

Table 12.1: Binder content calculation

Sample No. W1 (g)

W2 (g)

F1 (g) F2(g)

W3 (g)

Binder Content (%)

1

2

3

Final Binder Content (%) = Average of three samples

REFERENCES

(IRC: SP 11 1988 (Appendix - 5), ASTM D 2172-95, 1995, AASHTO T 164-08, 2008)

BITUMINOUS MIX DESIGN BY MARSHALL

METHOD (ASTM D1559, 1993)

OBJECTIVE

To determine optimum binder content of given bituminous mix by Marshall Method of Mix

Design

APPARATUS

Mould Assembly: Cylindrical moulds of 10 cm diameter and 7.5 cm height

consisting of a base plate and collar extension.

Sample Extractor

Compaction Pedestal and Hammer: Used to compact a specimen by 4.54 kg weight

with 45.7 cm height of fall.

Breaking Head: Used to test the specimen by applying a load on its periphery

perpendicular to its axis in a loading machine of 5 tones capacity at a rate of 5

cm/min.

Loading Machine: Measures the maximum load supported by the test specimen at a loading rate of 50.8 mm/min at 60 0C.

Flow Meter: An attached dial gauge measuring the flow value as a result of the loading in

0.25 mm increments.

Thermometers

Water Bath

Oven

Figure 13.1: Mould Assembly

Figure 13.2: Sample Extractor Figure 13.3: Loading Machine

Figure 13.4: Oven Figure 13.5: Compaction Pedestal and Hammer

PROCEDURE

In the Marshall test method of mix design three compacted samples are prepared for each

binder content. At least four binder contents are to be tested to get the optimum binder

content.

1) Prepare a mix of coarse aggregates, fine aggregates and mineral filler material in

such a proportion that final mix after blending has the graduation within the

specified range (Table 13.2).

2) Take approximately 1200 grams of aggregates and filler, and heat them to a temperature of 175 to 195 0C.

3) Clean the compaction mould assembly and rammer, and heat to a temperature of 100

to 145 0C. Heat the bitumen to a temperature of 121 to 138 0C and add the required

quantity of first trial percentage of bitumen to the heated aggregate and thoroughly

mix using a mechanical mixer or by hand mixing with trowel.

4) Then heat the mix at a temperature of 150to 160 0C.

5) Transfer the mix into the pre-heated mould and compact it by giving seventy five

blows on each side.

6) Soon after the compacted bituminous mix specimens have cooled to room

temperature, take the sample out of the mould using the sample extractor and

measure the weight, average thickness and diameter of the specimen. Weigh the

specimens in air and then in water.

7) Determine the theoretical specific gravity of the mix using the known specific gravity

values of different aggregates, filler and bitumen.

8) Calculate the bulk density value of the specimen from weight and volume.

9) Then immerse the specimen to be tested under water in a thermostatically controlled water bath maintained at 60 10C for 30 to 40 minutes.

10) Take out the specimens from the water bath and place them in the Marshall loading

machine to measure the marshal stability and flow values.

11) If the average height of the specimen is not exactly 63.5mm, then correct the

Marshall Stability value of each specimen by applying the appropriate correction

factor (Table 1).

12) Plot five graphs with values of bitumen content against the values of density,

Marshall Stability, voids in mineral aggregates(VMA), flow value and voids filled by

bitumen(VFB).

13) Let the bitumen contents corresponding to maximum density be B1, corresponding to

maximum stability be B2 and that corresponding to the specified voids content (at

4.0%) be B3. Then the optimum bitumen content for mix design is given by:

Bo= (B1+B2+B3)/3. RESULTS

The optimum Bitumen Content of the given mix, Bo =

DataSheet1 SpecificationforAggregateSelection

No. Sievesize(Passing)Specification

Range(%)Pass

OurSelection

%Retained

SampleWt.(g)

0 25.0mmto19.0mm 100 1 19.0mmto12.5mm 6695 2 12.5mmto9.5mm 5488 3 9.5mmto4.75mm 3770 4 4.75mmto2.36mm 2652 5 2.36mmto1.18mm 1840 6 1.18mmto600m 1330 7 600mto300m 8 23 8 300mto150m 6 16 9 150mto75m 4 10 10

DataSheet2

Table13.2:AggregateSpecifications

PercentbyPassingWeightSieveSize(mm) Type1

Basecourse

Type2Binderorlevelingcourse

Type3Wearingcourse

37.5 100 25 72100 100 19 6089 82100 10012.5 4676 6084 66959.5 4067 4974 54884.75 3054 3258 37702.36 2243 2345 26521.18 1536 1634 18400.6 1028 1225 13300.3 622 820 8230.15 414 513 6160.075 28 47 410Asphalt

cement(%by

weightoftotal

aggregate)

3.55.0 4.06.5 4.56.5

Table13.3:SpecificationsforMarshallProperties

VolumeofSpecimen(cm3)

Thicknessof

Specimen(mm)

CorrectionFactor

457470 57.1 1.19471482 68.7 1.14483495 60.3 1.09496508 61.9 1.04509522 63.5 1523535 65.1 0.96536546 66.7 0.93547559 68.3 0.89560573 69.9 0.86

Type1Basecourse Type2Binderorlevelingcourse Type3WearingcourseDescription

Min. Max. Min. Max. Min. Max.Marshallspecimens(ASTMD 1559)No.ofcomp.Blows,each

endofspecimen75 75 75

Stability,kg. 350 500 600 Flow,0.25mm 8 16 8 16 8 16

VMA 13 14 15 Airvoids,% 3 8 3 8 4 6

Aggregatevoidsfilledwithbitumen,% 60 80 65 85 70 85

Immersioncompression specimen(AASHTOT165)index

ofretainedstrength,%70 70 70

Figure13.6:TypicalplotsforMarshallTest

SUPERPAVE GYRATORY COMPACTOR (SGC) (AASHTO T 312-11, 2011)

OBJECTIVE

To prepare specimens of hot mix asphalt (HMA) using the Superpave gyratory

compactor to determine the volumetric and mechanical properties of the mixture

APPARATUS

Superpave Gyratory Compactor (SGC) meeting the requirements of AASHTO T 312

Molds meeting the requirements of AASHTO T 312

Chute, mold funnel or both (Optional)

Scale meeting the requirements of AASHTO M 231 Class G 5

Oven, thermostatically controlled, capable of maintaining set temperature

within 3C

Thermometers accurate to 1C between 10 and 232 C Note 1: Non-Contact thermometers are not acceptable.

Miscellaneous pans, spoons, spatulas, hot pads, gloves, paper discs, markers,

etc.

Fig14: superpave gyratory compactor

PROCEDURE

1) Prepare the laboratory asphalt mixture by batching the aggregates, mixing in

the proper amount of binder, conditioning the prepared mixture approximately

4700 g to provide enough material for a finished specimen height of 115 5

mm.

2) Turn on the power to compactor for the warm up period as recommended by

the manufacturer prior to the time the HMA is ready for compaction. 3)Check

the settings of the compacter,

-Internal Angle: 1.16 0.02

-Ram Pressure: 600 18 kPa

-Number of gyrations: (From Table 14.1)

4) Preheat the mold, base plate, and funnel in an oven at 93 C for 30-60 minutes

to prevent the asphalt mix from sticking to molds during the compaction

process and sticking in the funnel during sample preparation.

5) Heat the asphalt mixture in an oven at 132 C. When the asphalt mixture

reaches 132 C, remove the heated mold and base plate from the oven and

place a paper disk in the bottom of the mold.

6) Mix the entire sample to be compacted with a heated spoon and then carefully

put the sample in a funnel. With the funnel, place all the mixture into the

mold. With a heated spoon or spatula level the mix in the mold and place a

paper disk on the top.

7) Load the mold into the compactor and center the loading ram. Set the pressure,

angle setting, and gyrations per minute. Start the compactor and wait for the

compaction process to finish.

8) When completed, remove the mold assembly from the compactor. The

specimens can be removed immediately from the mold after compaction for

most HMA mixes. In order to insure the specimen does not get damaged, a

cooling period of 5 to 10 minutes in front of a fan may be necessary.

9) Remove the specimen with an extrusion jack. Remove the paper disks from the

top and bottom of the specimen.

Notes: Before testing, the gyratory compactor should be calibrated periodically for pressure, height, angle, and rotation to make sure compactor is within specifications.

RESULTS

Table 14.1: AASHTO R 35 Superpave Gyratory Compaction Effort

20-Year Design Traffic, ESALs (millions)

NDesign(Number of Design Gyrations)

< 0.3 50 0.3 to < 3 75 3 to < 10 100 10 to < 30 100

> 30 125

Number of Design Gyrations =

DYNAMIC CONE PENETROMETER

OBJECTIVE

To measure the in-situ strength and thickness of soil layers underlying the bound pavement layers

APPARATUS

Dynamic cone Penetrometer

Measuring scale

PROCEDURE

1) Assemble the DCP by attaching the cone tip, connect upper and lower shafts.

2) Test the soil layer beneath a bound pavement layer by cutting a hole through

the bound pavement layer of at least 50mm in diameter.

3) Place the DCP on the test surface or insert DCP in the center of the hole and

carryout seating operation.

4) Establish a reference for reading the penetration of the shaft after each blow; do

not record penetration during seating operation.

5) Raise the hammer to its upper limit and allow it to fall freely without lifting the shaft.

Note: Be careful to not influence the drop by forcing the hammer down. 6) Record the reading and the blow count by reading the shaft to the nearest

millimeter.

7) Repeat steps 5 and 6 until the cone is driven to the full depth of lower shaft, the

total penetration is less than 3mm for ten consecutive drops or the desired

depth is reached.

Note: Do not remove the DCP by forcefully striking the hammer against the handle. This will damage the DCP.

Figure 15. DynamicC onePenetrometer

RESULTS

The vertical movement of DCP cone produced by one drop of hammer,

Dynamic Penetration Index, DPI (mm/blow) = (PR2 PR1)/ (DN2 DN1)

=

Where, PR Penetration reading

Log10 (CBR) = 2.48-1.057 * Log10

(DPI) CBR =

BENKELMAN BEAM DEFLECTION MEASUREMENTS

(IS 2386(Part IV) - 1963, BS 812, Part 3, 1975)

OBJECTIVE

To determine the rebound deflection of a pavement surface

APPARATUS

A Benkelman beam

Figure 16: Benkelman Beam

A truck or trailer with an rear axle load of 8170kg equally distributed on two

dual tired wheels

A tire pressure of 5.6 kg/cm2 for loading the pavement

A thermometer with a range of 0-6 C in 1 C divisions

A mandrel suitable for making a 100mm deep hole in the pavement for

inserting the thermometer

A can containing either glycerol or oil for filling the thermometer hole

PROCEDURE

Calibration of Benkelman Beam

1. Calibrate the Benkelman Beam so that to ensure that the dial gauge and beam

are working correctly. This is done as described below.

2. Place the beam and level it on a hard surface.

3. Place a metallic block of known thickness under the probe and read the dial

gauge reading.

4. If the beam is in order then the dial gauge reading would be half of that of the

metallic block otherwise the dial gauge is checked and replaced if necessary.

5. If the dial gauge is functioning correctly then the beam pivot is checked for

smooth and free movements.

6. Check the dial gauge spindle beneath the striking plate to ensure that it is

tightly secured and has not become grooved by the dial gauge stylus.

Deflection measurements

Deflections shall be measured as follows:

1. Select a section of a road with preferable length not less than 1 km. In each of

these sections a minimum of 10 points are marked at equal distance to

measure deflections in the outer wheel path.

Note: For highway pavements following table should be referred to select the Test points.

The interval between the points should not be more than 50m in a lane. If for roads having more than one lane, mark the points on adjacent lanes in a staggered fashion.

Lane Width

(Meters)

Distance from lane Edge (Meters)

< 3.5 0.6

>3.5 0.9

Divided 4 lane Highway 1.5

If the highest or lowest deflection values in a group of ten differs from the

mean by more than one-third of mean then extra deflection measurements is

made at 25m on either side of point where high or low values are observed.

2. Centre the dual wheels of the truck above the selected point.

3. The probe of the Benkelman beam is inserted between the duals and placed on

the selected points.

4. Release the locking device and adjust the rear of the beam so that the plunger is

in contact with the stem of the dial gauge.

5. Set the dial gauge at approximately 1 cm and record the initial reading when

rate of deformation of the pavement is equal or less than 0.025 mm per

minute.

6. After initial reading is recorded, the truck is slowly driven a distance of 270 cm

and stopped.

7. Now record the dial gauge reading with truck at the above mentioned position

and note that the recording is done when the rate of recovery of the pavement

is equal to or less than 0.025mm per minute.

8. Move the truck further by 9m.

9. Record the final reading when the rate of recovery of the pavement is equal to less than

0.025 mm per minute.

10. Also record the pavement temperature at least once every hour inserting

thermometer in the standard hole with the hole filled with glycerol.

Note: Check the tire pressure at an interval of 2-3 hours and adjust to the standards

RESULTS

If (Di Df) 0.025 mm Actual deflection (XT) = 2 (Di Df)

=

If (Di - Df) > 0.025 mm,

Actual deflection (XT) = 2(Di Df) + 2.91 [2 (Df Di)]

=

1. Rebound Deflection= 2 x XT =

Table 16.1: Calculation of Rebound Deflection

Chainage

(m) Pavement

Temperature,

(0C)

Initial

Reading(D0)

(mm)

Intermediate Reading(Di)

(mm)

Final

Reading(Df)

(mm)

Rebound

Defection, x

(mm)

2. Mean deflection = x = x / n

=

3. Standard deviation = = ( ( x x )2 / n-1)

=

4. Characteristic Deflection = Dc = x + =

SOFTENING POINT OF BITUMEN

OBJECTIVES

To determine the softening point of bitumen within the range 30 to 157 oC by means of the Ring-and-Ball apparatus.

BACKGROUND

Unlike some substances (e.g. water which changes from solid to liquid at 0 oC) bituminous materials do not have a definite melting point. Instead, as the temperature rises, these materials slowly change from brittle or very thick and slow-flowing materials to softer and less viscous liquids. For this reason, the determination of 'softening point' must be made by a fixed, arbitrary and closely defined method if results are to be comparable.

Being very simple in concept and equipment, the Ring-and-Ball Test has remained a valuable consistency test for control in refining operations, particularly in the production of air-blown bitumens. It is also an indirect measure of viscosity or, rather, the temperature at which a given viscosity is evident. The softening point value has particular significance for materials which are to be used as thick films, such as joint

and crack fillers and roofing materials. A high softening point ensures that they will not flow in service. For a bitumen of a given penetration (determined at 25 oC), the higher the softening point the lower the temperature sensitivity

Research has shown that, for conventional paving grade bitumens, the Ring-andBall softening point temperature is the same as that which would give a penetration of 800 d-mm. This, together with the penetration at 25 oC, can be used to compute the Penetration Index. SUMMARY OF TEST METHOD (ASTM 1988)

Two horizontal disks of bitumen, cast in shouldered brass rings, are heated at a controlled rate in a liquid bath while each supports a steel ball. The softening point is reported as the mean of the temperatures at which the two disks soften enough to allow each ball, enveloped in bitumen, to fall a distance of 25 mm.

PROCEDURE (Figure 1)

1. Specimens are prepared exactly as specified (ASTM D36-95) in precisely dimensioned brass rings and maintained at a temperature of not less than 10 oC below the expected softening point for at least 30 minutes before the test.

2. The rings and assembly, and two ball bearings, are placed in a liquid bath filled

to a depth of 105 3 mm and the whole maintained at a temperature of 5 1 oC for 15 minutes. [Freshly boiled distilled water is used for bitumen with a softening point of 80 oC or below, and glycerine is used for softening point greater than 80 oC].

3. A 9.5 mm steel ball bearing (weighing 3.50 0.05 g) is centered on each

specimen and heat is then applied to the beaker so as to raise the temperature by 5 0.5 oC per minute.

4. The temperature at which each bitumen specimen touches the base plate is

recorded to the nearest 0.2oC.

RESULTS

Rigid adherence to the prescribed preparation of specimens and heating is absolutely essential for reproducibility of the results. The mean temperature of the two specimens (which shall not differ by more than 1 oC) is recorded as the softening point.

This temperature is to be used in conjunction with the penetration value to obtain the Penetration Index (PI).

Figure 17. Apparatus for the bitumen Softening Point Test (Millard, 1993)

DISCUSSION

(a) Report the source and type of bitumen. (b) Report the bath liquid used in the test and quote the mean softening point of your

specimen. Comment on the value obtained. (c) If the two test temperatures differ by more than 1oC, offer an explanation.

(d) Compile and compare results from other group(s).

REFERENCES

1. ASTM (1998). D36-95 Standard test method for softening point of bitumen (Ring-and-Ball Apparatus). 1998 Annual Books of ASTM Standards, Volume V04.04, American Society for Testing and Materials, Philadelphia, PA 19103-1187.

2. Millard, R.S. (1993). Road building in the Tropics. Transport Research Laboratory State-of-the-art Review 9, HMSO, London.

3. PWD (1992). PWD General Specification. Public Works Department, Singapore 1987 (with amendments, 1992).

Table 1: Requirements for 60/70 penetration grade bitumen (PWD 1992)

Property Requirement

Penetration at 25 oC, 100g, 5 s (deci-millimetre, d-mm) 60-70

Softening Point, ring and ball (oC) 47-56

Flash Point, Cleveland open cup (oC) Min. 232

Thin film oven test , 3.2 mm at 163 oC for 5 hours

Loss on heating (% by mass)

Penetration of residue at 25 oC (% of original penetration)

Ductility of residue at 25 oC at 5 cm/min (cm)

Max. 0.8

Min. 54

Min. 50

Solubility in trichloroethylene (% by mass) Min. 99

Specific gravity at 25 oC 1.0-1.11

TESTS ON BITUMINOUS MATERIAL

ISOLA BABAJIDE

129042071

IN PARTIAL FULFILMENT OF MASTERS OF SCIENCE IN CIVIL ENGINERING (HIGHWAY AND

TRAFFIC ENGINEERING)

DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING

FACULTY OF ENGINEERING

UNIVERSITY OF LAGOS

LAGOS

MARCH, 2014.