transportation lab presentation

CE328 Highway Materials Testing Experiments

ByDr. Tom. V. Mathew

IIT Bombay

List of Tests1. Aggregate crushing test 2. Aggregate impact test3. Abrasion Test (L.A. abrasion test) 4. Shape test (FI, EI, Angularity No.)5. Penetration Test6. Ductility Test7. Softening Point8. Marshall Stability Test9. Bitumen Extraction Test10.Traffic studies: Volume study

Requirements of Pavements

Types Flexible Pavement Rigid Pavement

Structural Requirements to withstand the design factors to serve during the design life / minimum

service life

Functional Requirements considering pavement deterioration considering road – user requirement

Flexible Pavements

Loading in FP

Overview

Pavement materials

Soil (sub-grade, embankment)

Aggregates (coarse, fine)

Binders (Bitumen, cement)

Aggregate

Aggregate is the major component of allmaterials used in road construction

It is used in granular bases and sub base,bituminous courses and in cement concretepavements

Desirable properties of Aggregate

Strength:The aggregate should be sufficiently strong to withstand the stresses due to traffic wheel load

Hardness: Aggregate should have hard enough to resist the wear due to abrasive action of traffic

Toughness: Aggregate should have resistance to impact or toughness

Durability: The aggregate used in pavement should resistance to disintegrationdue to the action of weather

Shape of aggregate: Should not be Flakyand elongated

Adhesion with Bitumen: Should have goodaffinity to bitumen

Desirable properties of Aggregate

Soil is all unindurated mineral material lying above rock strata including air, water, and organic matter

It is non-homogeneous and porous

Properties greatly influenced by moisture, density and compaction

A number of pavement failure is attributed to soil failures

Properties of soil

Shape of soil particles (bulky, flaky)

Particle size classification (clay, silt, sand, gravel)

Grain size distribution (sedimentation analysis for <75m)

Porosity and void ratio

Soil density (dry and wet density)

Properties of soil

Moisture-density relationship (Proctor density, OMC)

Chemical properties (Organic matter, minerals, pH)

Soil-water (Capillary water, water table)

Physical properties (Permeability, compressibility, shear resistance)

Petroleum distillation Flow Chart

Desirable Properties of Bitumen

It should be fluid enough at the time of mixing to

coat the aggregate evenly by a thin film

It should have low temperature susceptibility

It should show uniform viscosity characteristics

Bitumen should have good amount of volatiles in

it, and it should not lose them excessively when

subjected to higher temperature

The bitumen should be ductile and not brittle

The bitumen should be capable of being heated to thetemperature at which it can be easily mixed without anyfire hazards

The bitumen should have good affinity to the aggregateand should not be stripped off in the continuedpresence off water

Quality Control Tests: Soil

1. Gradation2. Atterberg Limits and indices (LL, PL,PI, SL)3. Laboratory Compaction (MDD and OMC)4. Field density test 5. CBR Test6. Plate bearing test

Quality control tests: Aggregate

1. Sieve analysis2. Aggregate crushing test3. Aggregate impact test4. Abrasion Test (L.A. abrasion test)5. Shape test (FI, EI, Angul. No.)6. Soundness Test 7. Specific gravity and Water absorption test 8. Stripping value test

1. Penetration2. Ductility3. Softening point4. Specific gravity5. Loss on heating6. Flash & Fire point7. Viscosity 8. Solubility

Quality control tests: Bitumen

California bearing ratio (CBR)

A simple test that compares the bearing capacity of a material with that of a well-graded crushed stone

A high quality crushed stone material should have a CBR of about 100%

CBR is basically a measure of strength

CBR value is the measure of resistance of material to the penetration of standard plunger under controlled density and moisture condition.

The CBR test can be made in the laboratory on undisturbed or remoulded soil samples.

The CBR value of sub grade is normally evaluated on a soaked sample compacted at optimum moisture content to maximum dry density.

Basic TestThis consists of causing a plunger of 50 mm

diameter to penetrate a soil sample at the rate of 1.25 mm/min.

The force (load) required to cause the penetration is plotted against measured penetration.

The loads at 2.5 mm and 5 mm penetration are recorded.

This load corresponding to 2.5 mm or 5 mm penetration is expressed as a percentage of standard load sustained by the crushed aggregates at the same penetration to obtain CBR value.

Definition of CBR

California bearing ratio is defined as the ratio (expressed as percentage) between the load sustained by the soil sample at a specified penetration of a standard plunger (50 mm diameter) and the load sustained by the standard crushed stones at the same penetration.

Standard Load values on Crushed Stones for Different Penetration Values

183360012.5

162318010.0

13426307.5

10520555.0

7013702.5

Unit StandardLoad, kg/cm2

StandardLoad, kg

Penetration,mm

Apparatus

Loading frame Cylindrical mould, Collar, Base Plate and

spacer Disc Compaction hammer Expansion Measuring Apparatus - Perforated

plate with adjustable stem, tripod and dial gauge reading to 0.01 mm

Annular Surcharge Weights

Loading MachineWith a capacity of at

least 5000 kg and equipped with a movable head or base that travels at an uniform rate of 1.25 mm/min.

Cylindrical MouldCylindrical mould with

inside diameter 150 mm and height 175 mm, provided with a detachable extension collar 50 mm height and a detachable perforated base plate 10 mm thick.

Compaction RammerWeight 2.6 kg with a

drop of 310 mm (or) Weight 4.89 kg a

drop 450 mm.

Adjustable stem, perforated plate, tripod and dial gauge

Preparation of Test Specimen

Prepare the remoulded specimen at Proctor’s maximum dry density or any other density at which C.B.R is required. Maintain the specimen at optimum moisture content or the field moisture as required. The material used should pass 20 mm I.S. sieve. Prepare the specimen either by dynamic compaction or by static compaction.

Dynamic Compaction

Take about 4.5 to 5.5 kg of soil and mix thoroughly with the required water.

Just before making the compacted mould of soil, take representative sample for determining water content.

Fix the extension collar and the base plate to the mould. Insert the spacer disc over the base. Place the filter paper on the top of the spacer disc.

Dynamic Compaction

Compact the soil in the mould using either light compaction or heavy compaction. For light compaction, compact the soil in 3 equal layers, each layer being given 55 blows by the 2.6 kg rammer. For heavy compaction compact the soil in 5 layers, by giving 56 blows to each layer by the 4.89 kg rammer.

Dynamic Compaction

Remove the collar and trim the specimen smooth and flush with the mould.Remove the base plate and the displacer disc,

weigh the mould with compacted soil, and determine the wet unit weight. Place a filter paper on the base plate, invert the

specimen (5 cm gap is on the top) and attach the base plate so that the soil is in contact with the filter paper on the base.

Penetration Test Place the mould assembly with the surcharge weights on the

penetration test machine. Seat the penetration piston at the center of the specimen with

the smallest possible load, but in no case in excess of 4 kg so that full contact of the piston on the sample is established.

Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the penetration rate is about 1.25 mm/min.

Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10 and 12.5 mm. Note the maximum load and corresponding penetration if it occurs for a penetration less than 12.5 mm.

Detach the mould from the loading equipment. Take about 20 to 50 g of soil from the top 3 cm layer and determine the moisture content.

757269585038

ProvingRing

Reading(div)

49.9533.3018.5011.103.70

Load onPlunger

12.5107.5543

Penetration(mm)

138.75133.20127.65107.3092.5070.30

Load onPlunger

272.5182101.56120.500

ProvingRing

Reading(div)

Penetration(mm)

Data from a Typical CBR Test for Sample No.1

0 2.5 5 7.5 10 12.5

Penetration

Load Vs Penetration Curve forSample No.1

Initial Concavity

The load – penetration curve may show initial concavity due to the following reasons:The top layer of the sample might have become

too soft due to soaking in water

The surface of the plunger or the surface of the sample might not be horizontal

Correction

Draw a tangent to the load-penetration curve where it changes concavity to convexity

The point of intersection of this tangent line with the x-axis is taken as the new origin

Shift the origin to this point (new origin) and correct all the penetration values

Corrected Penetration Values for Sample No.1

Computation of CBR for Sample No.1

Compute CBR at 2.5 mm penetrationCBR of Specimen at 2.5 mm penetration =

(80/1370)*100 = 5.84 %Compute CBR at 5 mm penetrationCBR of Specimen at 5 mm penetration =

(117/2055)*100 = 5.69 %

Variation in CBR Values

At least three samples should be tested on each type of soil at the same density and moisture content to take care of the variation in the valuesThis will enable a reliable average value to be

obtained in most casesWhere variation with in CBR values is more

than the permissible maximum variation the design CBR value should be the average of six samples and not three

Permissible Variation in CBR Value

± 531 and above

± 311-30

± 25-10

Maximum variationin CBR value

CBR (per cent)

Design CBRThe average CBR values corresponding to 2.5 mm

and 5 mm penetration values should be worked out

If the average CBR at 2.5 mm penetration is more than that at 5 mm penetration, then the design CBR is the average CBR at 2.5 mm penetration

If the CBR at 5mm penetration is more than that at 2.5 mm penetration, then the test should be repeated. Even after the repetition, if CBR at 5mm is more than CBR at 2.5 mm, CBR at 5 mm could be adopted as the design CBR.

5.71 %Design CBR

5.565.445.695.0 mm

5.765.545.842.5 mm

CBR (%)Penetration

Computation of Design CBR

1. Sieve Analysis

Significance of Test Each type of aggregate test

requires a specified aggregate size

(E.g. 10-12.5 mm for crushing test)

Each bituminous mix type has a recommended aggregate gradation

(% passing 26.5 mm in 55-90 for GSB1)

So aggregate is passed through a set of sieves to get material of various sizes

Sieves and Sieve-shaker

Procedure

Bring the sample to an air dry condition either by drying at room temperature or in oven at a temperature of 100oC to 110oC.Take the weight of the sample.

Clean all the sieves and sieve the sample successively on the appropriate sieves starting with the largest.

Shake each sieve separately over a clean tray.

On completion of sieving note down the weight of material retained on each sieve.

Report the results as cumulative percentage by weight of sample passing each of the sieves.

Observation Sheet

IS:2386 Part I; IS: 383

I.S. Sieve designation

Weight of sample

retained (gm)weight retained

Percent of

Cumulative percent of weight

retained (%)

Percentage passing

(%)63 mm40 mm20 mm

12.5 mm10 mm

4.75 mm

Observation Sheet

IS SeiveDesignation

Weight of sampleretained

Weightretained

Cumulativeweight

retained(%)

Passing (%)

63 100 6.25 6.25 93.7540 200 12.5 18.75 81.2520 400 25 43.75 56.25

12.5 400 25 68.75 31.2510 300 18.75 87.5 12.5

4.75 200 12.5 100 01600 100

Gradation chart

4.75 10 12.5 20 40 63 63

Gradation

1. Aggregate Crushing Test

Significance

Aggregate crushing value provides a relative measure of resistance to crushing under a gradually applied compressive load

Aggregates subjected to high stresses during rolling and severe abrasion under traffic

Also in India very severe stresses come on pavements due to rigid tyre rims of heavily loaded animal drawn vehicles

Test Set-up

Procedure Surface dry aggregates passing 12.5 mm and

retained on 10 mm selected

3.25 kg aggregate required for one test sample

Cylindrical measure filled with aggregates in 3 layers, tamping each layer 25 times

After leveling the aggregates at the top surface the test sample is weighed

The cylinder is now placed on the base plate

Contd….

The cylinder with the test sample and plunger in position is placed on compression machine

Load is applied at a rate of 4 tonnes per minute upto 40 tonnes

The crushed aggregate is taken out, sieved through 2.36 mm IS sieve and weighed to get material passing

Aggregate crushing value = W2*100/W1W2= Weight of crushed materialW1=Total weight of sample

Load Application

Sample being loaded in the compression machine at 4 T per minute for 10 minutes (upto 40 T)

Observation Sheet

Note: Value recorded up to first decimal place

Aggregate Crushing Value= W1/W2*100

Wt. of Aggregate SamplePassing 2.36 mm SieveAfter the Test= W2(gms)

Wt. of Aggregate SampleFilling in The Cylinder=W1(gms)

321Average

Test No.Observations

Observation Sheet

Observations Test No. Average1 2 3

Wt. of Aggregate SampleFilling in The Cylinder=W1 (gms)

362 354 343

Wt. of Aggregate SamplePassing 2.36 mm SieveAfter the Test= W2 (gms) 116 102 84

Aggregate Crushing Value =

W1 / W2 x 10032% 28.8 % 24.5 % 28.5 %

Note: Value recorded up to first decimal place

Specifications

45 %Max for

Other Surfaces

30 %Max for Surface

Course

As per IRC:15 1970

AndIS: 2386:Part IV

Aggregate Crushing Value for Cement Concrete PavementsSpecified By

Discussion Indirect measure of crushing strength

Low value indicate strong aggregates

Surface course need more strength than base course

Should not exceed 30% for cement concrete surface ,and 45% for others

2. Aggregate Impact Test

Significance This test assesses the suitability of aggregate as

regards the toughness for use in pavement construction

Road aggregates subjected to pounding action due to traffic loads- so possibility of breaking

Should be tough enough- so proper aggregates to be used

Suitability to be checked by laboratory tests

Test Set-up

Procedure

1. Aggregate passing through 12.5 mm IS sieve and retained on

10 mm sieve is filled in the cylindrical measure in 3 layers by

tamping each layer by 25 blows. Determine the net weight of

aggregate in the measure (W1)

2. Sample is transferred from the measure to the cup of

aggregate impact testing machine and compacted by tamping

25 times

3. The hammer is raised to height of 38 cm above the upper

surface of the aggregates in the cup and is allowed to fall freely

on the specimen

Test In progress

Contd….

After subjecting the test specimen to 15blows, the crushed aggregate is sieved through IS 2.36 mm sieve

Weigh the fraction passing through IS 2.36 mm sieve(W2)

Aggregate impact value = W2 / W1 x100

w2 = Weight of fines passing 2.36 mmw1 = Weight of sample

Mean of the two values reported

Observation Sheet

Note: Value Recorded to the Nearest Whole Number

Aggregate Impact Value=W2/W1*100

Wt. of Aggregate SamplePassing 2.36 mm SieveAfter the Test= W2(gms)

Wt. of Aggregate SampleFilling in The Cylinder=W1(gms)

321Avg

Test No.Observations

Observation SheetObservations

Test No.Avg

1 2 3Wt. of Aggregate SampleFilling in The Cylinder=W1 (gms)

319 323

Wt. of Aggregate SamplePassing 2.36 mm SieveAfter the Test= W2 (gms)

Aggregate Impact Value=

W2 / W1 x10020.37 21.05 21

Note: Value Recorded to the Nearest Whole Number

Specifications

30Bituminous Wearing SurfacesIS: 2386: Part IV and IRC:15 1970; MORTH: 2001

30WBM Surface course35

Bituminous Macadam, Basecourse

45Cement Concrete Base course

50WBM Sub-base course

Aggregate Impact Value, Max, %Type of Pavement Material/Layer

3. Los Angeles Abrasion Test

Significance It is resistance to wear or hardness of

aggregates

Road aggregates at the top subjected to wearing action

Under traffic loads abrasion/attrition action within the layers as well

To determine suitability, tests have to be carried out

Test Set-up

Procedure1. Aggregates dried in oven at 105 -110 ° C. to constant

weight conforming to any one of the gradings

E.g. 1250 gm of 40-25 mm, 1250 gm of 25-20 mm, 1250 gm of 20-12.5 mm, 1250 gm of 12.5-10 mm, with 12 steel balls

2. Aggregate weighing 5 kg or 10 kg is placed in cylinder of the machine ( W1 gms)

3. Machine is rotated at 30-33 rpm for 500 revolutions

4. Machine is stopped and complete material is taken out including dust

Grading Requirement

5000±2512-----50005000---G

5000±2512-----NA50005000--F

5000±2512-------500025002500E

5000±2565000---------D

5000±258-25002500-------C

5000±2511---25002500-----B

5000±2512---1250125012501250---A

Wt. of

Charge, g

No. of

Spheres

4.75-2.36

6.3-4.75

10-6.3

12.5-10

20-12.5

AbrasiveCharge

Wt. in gms of each Sample in the Size Range, mmGrading

After 500 – 1000 revolutions

Contd….

6. Sieved through 1.7 mm sieve

7. Weight passing is determined by washing the portion retained, oven drying and weighing (W2gms)

8. Aggregate abrasion value is determinedLAAV = W2 / W1 x100

W2 = Weight of fines passing 1.7 mmW1 = Weight of the sample

Specifications

60WBM Sub-base course

IS: 2386: Part IV; IRC:15 1970; IS: 383 30

Bituminous/Cement concrete Wearing course

35Bituminous Carpet, SD, Cement Concrete surface course

40WBM Surface course, BM binder course

50WBM Base course with bit. Surfacing, BM Base course

L. A. Abrasion Value, Max, %Type of Pavement Layer

Discussion

Select a grading close to the project for testing

Simulate both abrasion and impact due to wheel loads

It determines the hardness of the stone

4. Shape Tests

Determination of:

a.Flakiness Indexb.Elongation Indexc. Angularity Number

Significance Shape of crushed aggregates determined by the percentage of

flaky and elongated particles

Shape of gravel determined by its angularity number

Flaky and elongated aggregate particles tend to break under heavy traffic loads

Rounded aggregates preferred in cement concrete pavements as more workability at less water cement ratio

Angular shape preferred for granular courses/flexible pavement layers due to better interlocking and hence more stability

Test Set-up

Length Gauge for Elongation Index

Thickness Gauge for Flakiness Index

Procedure (Flakiness)

(a). Flakiness Index: The flakiness index of aggregates is the

percentage by weight of particles whose least dimension is less than

three-fifths (0.6) of their mean dimension. Applicable to sizes>= 6.3

1.The sample is sieved through IS sieve sizes 63, 50, 40, 31.5, 25,

20, 16, 12.5, 10 and 6.3 mm

2. Minimum 200 pieces of each fraction to be tested are taken and

weighed (W1 gm)

3. Separate the flaky material by using the standard thickness gauge

Flakiness Index Test in Progress

Flakiness

The amount of flaky material is weighed to an accuracy of 0.1 percent of the test sample

If W1, W2, …, Wi are the total weights of each size of aggregates taken

If w1, w2, …, wi are the weights of material passing the different thickness gauges then:

%100%100....)(....)(

WWwwFI

Observation sheet (Flakiness Index)

Passing through

I.S. Seive, (mm)

Retained on I.S. Seive, (mm)

63 50 W1= 23.9 w1=50 40 W2= 27 w2=40 31.5 W3= 19.5 w3=

31.5 25 W4= 16.95 w4=25 20 W5= 13.5 w5=20 16 W6= 10.8 w6=16 12.5 W7= 8.55 w7=

12.5 10 W8= 6.75 w8=10 6.3 W9= 4.89 w9=

Total W= w=

Size of aggregate Wt. Of the fraction

consisting of at least 200

pieces (gm)

Thickness gauge size,

(0.6 times the mean sieve)

Weight of aggregate in each fraction passing thickness gauge

Elongation IndexElongation Index: The percentage by weight of particles whose greatest dimension is greater than one and four fifth times (1.8 times) their mean dimension. Applicable to sizes >=6.3 mm

1. The sample is sieved through sieve sizes, 50, 40, 25, 20, 16, 12.5, 10 and 6.3

2. Minimum 200 pieces of each fraction to be tested are taken and weighed (W1 gm)

3. Separate the elongated material by using the standard

length gauge

Elongation Index Test in Progress

Elongation Index

The amount of elongated material is weighed to an accuracy of 0.1 percent of the test sample

If W1, W2, …, Wi are the total weights of each size of aggregates taken

If w1, w2, …, wi are the weights of material retained on different thickness gauges then:

%100%100....)(....)(

WWwwEI

Observation sheet (Elongation Index)

Passing through

I.S. Seive, (mm)

Retained on I.S. Seive, (mm)

50 40 W1= 81 w1=40 25 W2= 58 w2=25 20 W3= 40.5 w3=20 16 W4= 32.4 w4=16 12.5 W5= 25.5 w5=

12.5 10 W6= 20.2 w6=10 6.3 W7= 14.7 w7=

Total W= w=

Size of aggregateWt. Of the

fraction consisting of at least 200 pieces (gm)

Length gauge size, (1.8 times the mean

sieve) (mm)

Weight of aggregate in each fraction retained on

length gauge (gms)

Specifications

15(do)Bit. Macadam, WBM base & surfacing course

IS: 2386, Part I; IRC: 14-48 ; MORTH: 2001

35Cement Concrete

25(do)Asphaltic concretePenetration macadamBit. Surface dressing

30(Combined FI and EI)Bituminous carpet

Limit of Flakiness Index(%)Type of pavement construction

Angularity number

The angularity number measures the percent voids in excess of 33 percent which is obtained in the case of the most rounded gravel particles.

Range: 0-11 (rounded gravel-crushed angular)

1. The cylinder is calibrated by determining the weight of water at 27oC required to fill it

2. Aggregate is sieved through 20, 16, 12.5, 10, 6.3 and 4.75 mm IS sieves

3. About 10 kg of the predominant size should be available

Test in Progress

Contd….

4. The sample of single-size aggregate is dried in an oven at 100o

to 110oC for 24 hours and then cooled

5. The scoop is filled with aggregate which is allowed to slide gently into the cylinder from the lowest possible height

6. The aggregate is filled in three layers, tamping each layer evenly 100 times with a tamping rod

7. After the third layer is tamped, the aggregates are struck off level with the help of tamping rod and surface finished

8. The aggregate with cylinder is now weighed to the nearest 5 g. The mean weight of aggregate is found

Calculations and Observation SheetAngularity number AN = 67 - W x 100

G x Cwhere, W = mean weight of aggregates in the cylinder,g

C = Weight of water required to fill the cylinder,gG = Specific gravity of aggregate (2.71)

Weight of water filling the cylinder = C g = Specific gravity of the aggregate = G =

ParticularsTrial number

Mean1 2 3

Weight of aggregate filling thecylinder to the nearest five grams, g 4185 4195 4190Mean weight of aggregate filling the cylinder, Wt =2870Angularity Number = 67 – { (4190/2.71x100)/C } = 13

Discussion

Elongated, flaky and angular materials decreases the workability of the mix, and not preferred in cement concrete

Angular aggregates are preferred in flexible pavement at WBM / WMM

Angularity number ranges from zero for perfectly rounded aggregate (rounded pebbles) to about 11 percent for freshly crushed aggregates

But for DBM & BC mix design may be modified to incorporate high angularity number

5. Penetration test

Significance

The penetration test determine the hardness or softness of bitumen

The bitumen grade is specified in terms of the penetration value

30/40 and 80/100 grade bitumen are commonly used

In hot climates a lower penetration grade bitumen is preferred and vise versa

Significance

Consistency of bitumen varies with temperature, constituents, refining process, etc.

Viscosity is an absolute property, but could not be determined easily

Viscosity of cutback bitumen by indirect method (orifice viscometer)

Too soft for penetration, too hard for orifice then perform float test

Significance

Basic principle of penetration test:measurement of penetration in units of 1/10th of a mm of a standard needle of 100 gm in a bitumen sample kept at 25°C for 5 seconds

Higher penetration implies softer grade

Purpose is classification

FigurePenetrometere Water Bath

Weight

NeedleMould

Temperature Controller

Procedure Heat the bitumen to softening point +900 C

Pour the bitumen into the container at least 10 mm above the

expected penetration

Place all the sample containers to cool in atmospheric temperature

for 1 hour

Place the sample containers in temperature controlled water bath at

a temperature of 250 C ± 1o C for a period of 1 hour

Fill the transfer dish with water from the water bath to cover the

container completely

Continue. . . .

Take off the sample container from the water bath,place in transfer dish and place under the middle ofpenetrometer

Adjust the needle to make a contact with surface of the

sample

See the dial reading and release the needle exactly for

5 seconds

Note the final reading

Difference between the initial and final readings is taken

as the penetration value in 1/10th of mm

Penetro-meter dial readings

Sample No 1 Sample No 2

Test 1

Test 2

Test 3

Mean value

Test 1

Test 2

Test 3

Mean value

Initial 0 0 0

Final 85 85 75

Average Value = 82 (Grade is 80/100)

(i) Pouring temperature = 100 oC

(ii) Period of cooling in atmosphere, minutes = 60 mts(iii) Room temperature = 27 oC

(iv) Period of cooling in water bath, minutes = 60 mts

(v) Actual test temperature = 25 oC

Observation Sheet

IS Specifications

7%Above 225

5%80-225

4%0-80

RepeatabilityPenetration Grade

175-22580-10060-7040-5030-4020-30Penetration Value

A200 & S200

A90 &S90

A65 &S65

A45 & S45

A35 &S35A25Bitumen

Discussion

Test is highly influenced by the pouring temperature, size of needle, weight of needle, test temperature, duration of release of needle

IRC suggests 30/40, 60/70, 80/100 for BM

High penetration grade is desirable in colder regions

Penetration below 20 will result in cracking

For lower penetration, bonding is difficult, but once achieved will remain for a long time

6. Ductility Test

Ductility Machine

Significance

The ductility of bitumen improves the physicalinterlocking of the aggregate bitumen mixes

Under traffic loads the pavement layer is subjected torepeated deformation. The binder material of lowductility would crack and thus provide perviouspavement surface

The test is believed to measure the adhesive property ofbitumen and its ability to stretch

Significance

Ductility and penetration go together, in general, but exception can happen

Ductility is the distance in cm to which a standard briquette of bitumen can be stretched before the thread breaks

Ductile materials is one which elongates when held in tension

Procedure The bitumen sample is melted to temperature of 75oC to

100oC above the approx. softening point until it is fluid

It is strained through IS sieve 30, poured in mould

assembly and placed on a brass plate, after a solution of

glycerine or dextrine is applied over all surfaces of the

mould exposed to bitumen

Thirty to forty minutes after the sample is poured into the

moulds, the plate assembly along with the sample is

placed in water bath maintained at 27oC for 30 minutes

Briquette Moulds

Continue. . . .

The sample and mould assembly are removedfrom water bath and excess bitumen material is cutoff by leveling the surface using hot knife

After trimming the specimen, the mould assembly

containing sample is replaced in water bath

maintained at 27oC for 85 to 95 minutes

The slides of the mould are then removed and the

clips are carefully hooked on the machine without

causing any initial strain

The pointer is set to read zero

Ductilometer In Operation

Continue. . . .

The machine is started and the two clips are thuspulled apart horizontally

While the test is in operation, it is checked whether

the sample is immersed in water up to a depth of at

least 10mm

The distance at which the bitumen thread breaks is

recorded (in cm) and reported as ductility value

Breaking of Thread

Observation sheet(i) Grade of bitumen = 60/70(ii) Pouring temperature °C = 100 oC(iii) Test temperature = 27 oC(iv) Period of cooling (minutes) in Air = 40 min

In water bath before trimming = 30 minIn water bath after trimming = 90 min

Test PropertyBriquette Number Mean

Valuea b cDuctility (cm) 74 76 75

Repeatability %

Reproducibility %

IS Specification

Note: S denotes sources other than Assam petroleum

75S 45,S 65 & S 90

50S 35

Minimum Ductility (cm)

Source of Paving Bitumen & Penetration Grade

10%Reproducibility

5%Repeatability

Discussion

Ductility of bitumen is affected by the pouring temperature, briquette size, placement of briquette, test temperature, rate of pulling

Ductility value ranges from 5-100. Low value implies cracking. Some minimum ductility is needed for flexural strength

The lack of ductility does not necessarily indicate poor quality.

7. Softening Point

Significance

Bitumen does not melt, but change gradually from solid to liquid

Softening point is the temperature at which the bitumen attains particular degree of softening under specified test conditions

Ring and ball apparatus is used for the test

Ring & Ball Test Set-up

Glass Beaker

Brass Rings(In Ø=15.9 Mm & Out Ø=17.5mm

Steel Balls ø = 9.5 mm (2.5g)

Metallic Support

Thermometer

Mechanical Stirrer

Temp Controlled Heating Plate

Procedure Heat the bitumen to a temperature between 125oC to

Heat the rings at the same temperature on a hot plate

& place on glass plate coated with glycerin

Fill up the rings with bitumen

Cool for 30 minutes in air and level the surface with

a hot knife

Set the rings in the assembly and place in the bath

containing distilled water at 5oC and maintain that

temperature for 15 minutes

Continue….

Place the balls on the rings

Raise the temperature uniformly at 5oC per minute till

the ball passes trough the rings

Note the temperature at which each of the ball and

sample touches the bottom plate of the support

Temperature shall be recorded as the softening point

of the bitumen

Observation table(i) Grade of bitumen = 60/70(ii) Approximate softening point = 40 oC(iii) Liquid used in water bath(water/Glycerin) = water(iv) Period of air cooling (minutes) = 30 min(v) Period of cooling in water bath(minutes) = 15 min

Test PropertySample

a b meanTemperature at each sample

touches bottom plate 42 42 42

Repeatability %

Reproducibility %

IS SpecificationsSoftening Point Repeatability (oC) Reproducibility (oC)

<30oC 2 4

30oC- 80oC 1 2

>80oC 2 4

Bitumen Grades Softening Point (oc)S 35 55-65

A 45, S 45 & A 65 45-60S 65 40-55

A 90 & S 90 35-50A 200 & S 200 30-45

Note: S denotes sources other than Assam petroleum

Discussion

Test is affected by quality of liquid, weight of ball, rate of heating etc

It gives an idea of the temperature at which the bituminous material attains a certain viscosity

Bitumen with higher softening point is used in warmer places

Softening point is very critical for thick films like joint and crack fillers, to ensure they will not flow

Marshall Mix Design

CE 328 Transportation Engineering I

Overview

• Specimen preparation• Properties of the mix• Marshall stability and flow• Optimum bitumen content• Numerical examples

1/4/2012 Marshall Mix Design 134

1/4/2012 Dry Mix Design 135

Gradation for BC surface course of 40 mm

Specimen preparation• Approximately 1200gm of aggregates and

filler is heated to temperature of 1750-1900 C

• Bitumen is heated to a temperature of 1210-1250 C with first trial percentage of bitumen (say 3.5 or 4% by weight of the mineral aggregates)

• Heated aggregates and bitumen are thoroughly mixed at a temperature of 1540-1600 C

Marshall Mix Design1/4/2012 136

Specimen preparation• Mix is placed in a preheated

mould and compacted by a rammer with 50 blows on either side at temperature of 1380 C to 1490 C

• Weight of mixed aggregates taken for the preparation of the specimen may be suitably altered to obtain a compacted thickness of 63.5+/-3 mm

Specimen preparation

Thickness63.5+/-3 mm

Diameter 100 mm

Properties of the mix• Theoretical specific gravity Gt

• Bulk specific gravity of the mix Gm

• Percent air voids Vv

• Percent volume of bitumen Vb

• Percent void in mixed aggregate VMA • Percent voids filled with bitumen VFB

Phase diagram of a bituminous mix

Theoretical specic gravity of mix Gt

• Specific gravity without considering air voids

• Where W1: Weight of coarse aggregate in total mixW2: Weight of fine aggregate in total mixW3: Weight of filler in total mix

Wb: Weight of bitumen in total mix

G1: Apparent specific gravity of coarse aggregate

G2: Apparent specific gravity of fine aggregate

G3: Apparent specific gravity of filler

Gb: Apparent specific gravity of bitumen

Bulk specific gravity of mix Gm

• Specific gravity considering air voids

• Where Wm: Weight of mix in airWw: Weight of mix in waterWm - Ww gives the volume of the mix

Air voids percent Vv

• Percent of air voids by volume in the specimen

Gt: Theoretical specific gravity of mix

Gm: Bulk or actual specific gravity of mix

Air voids percent Vv

Percent volume of bitumen Vb

• Percent of volume of bitumen

• W1: Wt of coarse agg.W2: Wt of fine agg.W3: Wt of fillerWb: Wt of bitumenGb: Sp. Gr. of bitumenGm: Bulk sp. gravity

Voids in mineral aggregate VMA• Volume of voids in aggregates• Sum of air voids & volume of bitumen

VMA = Vv + Vb

• where Vv: Percent air voids in the mix• Vb: Percent bitumen content in mix

Voids filled with bitumen VFB• Voids in mineral aggregate frame work

filled with the bitumen

VFB = Vb / VMA X 100

• Vb: Percent bitumen content in mix

VMA: Percent voids in mineral aggregate

1/4/2012

Marshall stability and Flow value• Marshall stability and flow test provides the

performance prediction measure

• Stability portion of test measures maximum load supported by test specimen at a loading rate of 50.8 mm/min

• Load is applied to the specimen till failure, and maximum load is designated as stability

Marshall stability and Flow value• During the loading, an attached dial

gauge measures the specimen's plastic flow (deformation) due to the loading

• Flow value is recorded in 0.25 mm (0.01 inch) increments at the same time when the maximum load is recorded

Marshall stability and Flow value• Marshall Stability

– Maximum load required to produce failure when specimen is preheated to a prescribed temperature placed in a special test head and the load is applied at a constant strain (5 cm per minute)

• Flow Value– The deformation at failure point expressed in

units of 0.25 mm

Marshall stability and Flow value

Apply stability correction• It is possible while making the specimen

thickness slightly vary from standard specification of 63.5mm

• Measured stability values need to be corrected to those which would have been obtained if specimens had been exactly 63.5mm

• Multiplying each measured stability value by an appropriated correlation factors

Correction factors for Marshall stability values

Prepare graphical plots• Vary the bitumen content in the next trial by

+ 0.5 % and repeat the above procedure. • Number of trials are predetermined.• Marshall

Test Setup

Prepare graphical plots1. Binder content versus corrected

Marshall stability2. Binder content versus Marshall ow3. Binder content versus percentage of

void (Vv) in the total mix4. Binder content versus voids filled

with bitumen (VFB)5. Binder content versus unit weight or

bulk specic gravity (Gm)Marshall Mix Design1/4/2012 156

Marshal graphical plots

Determine optimum bitumen content• Average bitumen contents from:

1. Binder content Vs Stability2. Binder content Vs Gm3. Binder content at design Vv

Air voids Vv = 4%

Marshal graphical plots

Determine optimum bitumen content• The stability value, flow value, and VFB are

checked with Marshall mix design specification chart

• Mixes with very high stability value and low flow value are not desirable as the pavements constructed with such mixes are likely to develop cracks due to heavy moving loads

Marshall mix design specification

Numerical example - 1• The specific gravities and weight proportions

for aggregate and bitumen are as under for the preparation of Marshall mix design

• Volume and weight of one Marshall specimen was found to be 475 cc and 1100 gm

• Assuming absorption of bitumen in aggregate is zero

• Find Vv, Vb, VMA and VFBMarshall Mix Design1/4/2012 162

Solution

Numerical example - 2• The results of Marshall test for five

specimens is given below. Find the optimum bitumen content of the mix

Solution• Plot the graphs• bitumen content corresponding to

1. Max stability = 5 %2. Max Gm = 5 %3. 4% air void = 3 %

• Optimum bitumen content = 4.33 %– average of above– Design bitumen content

Thank You

tomvmathew@gmail.com

8. Marshall Stability Test

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