FINAL Asphalt Mix Design.doc

8/14/2019 FINAL Asphalt Mix Design.doc

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ACKNOWLEDGEMENT

Without the help of certain individual this project would have

completed. First and foremost we would like to thank God for giving us

the strength to do this project. Secondly we would like to thank Mrs. E.

Burrowes the construction a! "echnician and Mr. G. #oomes the

construction a! "echnician$ who displayed unwavering patience and

understanding when assisting us to carry out the various la!oratory

tests% she was always approacha!le even though sometimes our

&uestions were repeatedly asked. We are especially grateful for her

kind words of encouragement when we were in despair.

We would also like to thank Mr. ' (ryee$ for her input as our tutor and

for providing us with the fundamental start that was needed to do this

project.

Prepare by: T. Smith, S. Ashman and C. Francis Asphalt mix design project 1


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OBJECTIVE

"he main purpose of this project is to create a suita!le (sphalt Mi)

*esign which fulfills all the necessary properties of fle)i!ility$

dura!ility$ and worka!ility$ without sacrificing resistance to permanent

deformation.

THEORY

+avements are !uilt,up surfaces which provide a smooth surface for

the safe passage of vehicle under any weather condition and also

distri!ute vehicular loads to the underlying su! grade. "here are two

types of pavements-

Flexible Pavemen!

Ri"i# Pavemen!

n Fle)i!le +avements loads are transmitted downward from one layer

to the other% from the !ase layer$ to the su! !ase layer and finally to

the su! grade. "he Base layer is located immediately !elow the

wearing surface of the pavement and its main function is to increase

stiffness$ reduce fatigue$ distri!ute loads through the given thickness

of the pavement and provide drainage for the pavement. /ne factor

which plays a very integral role in the a!ility of the !ase layer to



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distri!ute load is the /ptimum moisture content. /ptimum moisture

content$ in short$ represents the amount of water content which will

produce the ma)imum material density. /ptimum moisture content is

usually plotted against density of material on a graph. "he density of

the material at the /ptimum moisture content is known as the

Ma)imum *ry *ensity.

"he Su! !ase layer is located !etween the Base layer and the Su!

grade layer. "he Su! !ase layer serves as a su!stitute for the su!

grade layer$ in terms of strength$ where the su! grade is e)tremely

weak. "he su! !ase also provides resistance to capillary action and

prevents frost action in the pavement. "he design of the su! !ase may

!e affected !y the mount of traffic e)pected$ position of water ta!le

and also the type of soil within the su! grade and its condition.

"he su! grade represents the natural ground on which the entire

pavement rests. ts function is to provide the necessary !earing

capacity for the load that is transferred to it !y the pavement. "he

performance of the pavement is directly related to the strength of the

su! grade. Factors affecting its performance include% density$ moisture

content$ eases of compaction$ permanency of compaction and

drainage. "he su! grade can !e strengthened !y soil sta!ili0ation$

water pumping and the implementation of good drainage systems.

n #igid +avements$ loads are transmitted directly to the su! grade

layer. #igid +avements are usually constructed using +ortland cement



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concrete due to the high modulus of elasticity and rigidity the

pavement. "he !asic type of concrete pavement consists of a mi)ture

of coarse aggregate$ fine aggregate$ +ortland cement$ water and

admi)tures. "hey are mostly used for highways su!jected to severe

service conditions such as ur!an highways$ rural highways and

runways.

+avements are classified according to the type of surfacing materials

used. "he Bituminous surface treatment and +ortland cement concrete

surface treatment$ !ut for this project emphasis will !e placed on the

!ituminous surfacing materials.

Bitumen can !e descri!ed as a !lack sticky or viscous su!stance used

as an adhesive or water proof on !uildings and road construction. t

consists of hydro car!on and three derivatives which are solu!le in

car!on dio sulphate and are soften gradually when heated. "he

hydrocar!ons that make up !itumen can generally !e made up of the

following-

(sphaltenes

#esins

/ils

A!$%alene!are large$ high,molecular,weight hydrocar!on fractions

precipitated from asphalt !y a designated paraffinic naphtha solvent at

a specified solvent,asphalt ratio. (sphaltenes have a car!on,to,

hydrogen ratio of 1.2. (sphaltenes constitute the !ody of the asphalt.



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#esins are hydrocar!on molecules with a car!on,to,hydrogen ratio of

more than 1.3 !ut less than 1.2. #esins affect the adhesiveness and

ductility properties of asphalt. /ils are hydrocar!on molecules with a

car!on,to,hydrogen ratio of less than 1.3. /ils influence the viscosity

and flow of the asphalt.

"he term 4!ituminous !inder5 includes 4coal tar5$ 4natural asphalt5 and

!itumen o!tained from petroleum crude 6petroleum !itumen7. "ars

with suita!le properties are now not widely availa!le. t is o!tained !y

refinery processes from petroleum. Bitumen can also !e found in

natural deposits or as a component of naturally occurring 6native7

asphalt which is associated with mineral matter.

8ative asphalt occurs when petroleum rises to the earth5s curst and

the volatile oils are evaporated. "hese native asphalts were found in

pools and asphalt lakes. /ne of the more well,known deposits of native

asphalts is the 9"rinidad ake: deposit on the island of "rinidad off the

north coast of South (merica. Before the development of the

processes for producing asphalt cement from crude petroleum

products$ native asphalts were the only sources of supply for early

pavement projects. "he first asphalted pavement was !uilt in ;23< in

ondon$ England. ( year later construction of road and street

pavements !egan in the =nited States in 8ewark$ 8ew 'ersey.

With the invention of the automo!ile$ which re&uired smooth all,

weather pavements$ the demand for asphaltic pavements grew. "hus$



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the process for producing asphalt cement from crude petroleum

products grew$ which led to the development of modern asphalt

cement.

(sphalt cement is a valua!le !y,product o!tained when petroleum5s

are processed to o!tain gasoline$ kerosene$ fuel oil 6diesel and

lu!ricating7 and other asphalt products. "here are three types of

petroleum found in the earth5s crust-

A!$%ali&'ba!e &()#e *il!

Pa(a++in'ba!e &()#e *il!

Mixe#'ba!e &()#e *il!,

(sphaltic,!ase crude oils are used to derive A!$%al &emen !y a

straight,run distillation process. (sphalt cement may also !e o!tained

from mi)ed,!ase crude oils !ut the process is very complicated.

Bituminous products may !e o!tained form paraffin,!ase crude oils !y

a destructive distillation process involving chemical changes. "hese

!ituminous materials should not !e classified as asphalt.

(sphaltic concrete is made up of mi)ture of coarse aggregate$ fine

aggregate$ mineral filler and !itumen$ well proportioned in order to

minimi0e cost !y producing the most suita!le asphaltic concrete yields

a pavement that is sta!le$ dura!le$ fle)i!le and skid resistant. t is not

always possi!le to optimi0e all four properties% thus$ compromises are

often made.

+avements have certain properties-



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$*li!%in". Pavemen blee#in"occurs when too few voids are left in

the mi) and traffic loads compact the pavement on a hot day$ forcing

asphalt to the surface of the roadway. "his action covers the e)posed

rough aggregate and the pavement !ecomes slippery. With voids in

pavements as low as @ or ; percent$ slippery pavements will not

occur$ however$ most specifications re&uire A or percent air voids to

prevent surface !leeding.

A""(e"ae $*li!%in" results after a pavement receives continuous

wear form traffic and the surface aggregates polish$ forming a slippery

pavement. +olishing can !e reduced !y using relatively hard

aggregates.

(s mentioned earlier it is very hard achieve all properties$ hence

sacrifices have to !e made. E)ample$ !y ma)imi0ing dura!ility$ !oth

sta!ility and skid resistance are compromised. Sta!ility is

compromised when thick coatings of asphalt are placed over the

aggregates and causes the !onding !etween aggregates and asphalt

cement to lessen 6as the aggregates tend to float in the asphalt7. Skid

resistance is compromised as a)le loads tend to compact a pavement

which has more asphalt than needed to cover the aggregates$ causing

!leeding of the asphalt and there!y creating a slippery surface.

"his project however will emphasi0e on (sphalt mi) *esign and not

road construction.



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"he design of hot mi)es are mainly a matter of selecting and

proportioning ingredients to o!tain the desired finished construction

properties i.e. the proper si0e and gradation of coarse and fine

aggregates$ filler and the !itumen grade. "he aim is to find an

economical !lend and gradation of aggregates and asphalt 6within the

specification limits7 that yields a mi) to have-

Enough asphalt to ensure a dura!le$ compacted pavement !y

thoroughly coating$ !onding and waterproofing the aggregate.

Enough mi) sta!ility to satisfy the demands of traffic without

distortion or displacement.

Coids in the total compacted mi) sufficient that will permit a

slight amount of added compaction under traffic loading without

!leeding or loss of sta!ility. >owever$ the volume of voids should

!e at a minimum to keep out harmful air and moisture content.

Enough worka!ility to allow placement and proper compaction of

the paving mi) without any segregation.

"here are four essential specifications which give an indication

of the mi) properties- "he voids in mineral aggregates 6CM(7$ (ir

voids$ Marshall Sta!ility and Flow.

"he Marshall Sta!ility and flow are determined from the

e)periment. *uring the mi)ing procedures asphalt mi) is

compacted in a cylindrical mould and cured under re&uired



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conditions. "he resulting !ri&uette is then loaded and its strength

to failure 6sta!ility7 and its deformation 6flow7 are measured.

"he voids in mineral aggregate 6CM(7 ensures that the aggregate

grading is not too dense. (ggregate grading which is too dense

will prevent ade&uate coating of the particles which is essential

for the sta!ility and dura!ility of the mi). Within the CM($ there

has to !e air voids which will allow for some compaction of the

pavement$ without forcing asphalt to the surface$ creating

pro!lems such as !leeding and low skid resistance.

(fter the aggregates meeting the specifications have !een

selected$ the optimum asphalt cement content is determined.

(sphalt cement is the most e)pensive constituent of the mi)ed%

therefore its conservation will !e very economical.

"he optimum asphalt cement is usually found through varying the

asphalt cement contents !y increments of 1.D$ 6!y weight7

typically commencing at .1 through to a ma)imum of ;1. t is

not normally necessary to take more than five 6D7 different

asphalt cement contents. "rial mi)es are then done at these

selected ( contents and the following parameters are measured-

o Marshall Sta!ility$

o Flow$

o Bulk density of compacted !ri&uettes$

o Ma)imum #elative density$

o (ir voids



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o Coids in Mineral (ggregates 6CM(7.

"he results of the parameters are then plotted against the (

contents and the optimum ( content selected !ased on the

following specified criteria-

o "he Medium air voids$

o "he ma)imum !ulk relative density of !ri&uettes

o "he ma)imum sta!ility.

"he average ( content is then used to check for compliance with

the si) specifications to ensure that they are met !efore making a

decision to accept this average as the optimum asphalt cement

content.

THE -TANDARD PENETRATION TE-T

AIM0

"o determine the penetration of semi,solid and solid !ituminousmaterial

APPARATUS



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+enetration (pparatus

+enetration needles

Sample container 6metal7

"hermometer

Water !ath

"ransfer dish 6D11 ml7

"imer

THEORY

"he penetration test is used as a measure of consistency$ !y

measuring at a fi)ed temperature. >igher values of penetration

indicate softer consistency. "he sample is melted and cooled under

controlled conditions. "he penetration is measured with a penetometer

!y means of which a standard needle is applied to the sample under

specific conditions.

( needle of standardi0ed dimensions is allowed to penetrate into a

sample of the !itumen under normal conditions at temperature of

A2o$ under a load of ;11g$ for a time of D seconds. "he amount of

indentation$ in units of 1.;mm$ is termed the 4penetration5.

FLA-H POINT TE-T

AIM:



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"o determine the flash point of asphalt or !itumen$ using of the

leveland /pen up apparatus.

APPARATUS

leveland /pen up (pparatus

Bunsen flame with +G supply

"hermometer

THEORY

"he flash point test is done to determine the temperature at which the

asphalt will ignite. Bitumen with a low flash point usually indicates

contamination !y other fuel oils of lower !oiling point. =sing asphalt

with a flash point at road pavement temperatures will result in a road

surface that will easily ignite under pavement conditions. (lso$ the

flash point test is done to ensure safety in the la!$ since the asphalt

will !e handled at high temperatures. f the temperature at which the

asphalt is !eing handled e)ceeds the flash point$ the asphalt !ecomes

a potential ha0ard for !urns and for poisoning !y way of the inhalation

of no)ious su!stances.

/ther tests that give characteri0ation of !ituminous materials are- ,

Specific Gravity$ *uctility$ Float "est$ Stiffness Modulus$ Sampling

Bituminous Materials$ Fraass !reaking +oint and Ciscosity. a!oratory

tests include the 4loss on heating test5 and the 4rolling thin film oven

test5. 8o detailed consideration of these other tests is given in this



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report. Suffice it to say that these tests$ if carried out$ must !e

referenced to an appropriate standard$ the latest version of which

must always !e fully complied with. (lso$ it is assumed that there is

familiarity with the tests for suita!ility and properties of aggregates.



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SOFTENING POINT TEST

"he second method of defining hardness or consistency is to determine

the temperature at which a fi)ed consistency occurs. "he test is

carried out !y recording the temperature$ at which the !itumen softens

sufficiently to allow a steel !all$ placed on a sample of the !itumen$ to

fall a fi)ed distance$ when the temperature is raised at a specified rate.

8o change in the physical state of the !itumen occurs and the

softening point must not !e treated as the melting point. Softening

points can vary from ADo to ;A1o.

APPARATUS

Bunsen flame with +G supply

"hermometer

Shield

Glass container

#ing apparatus

Water !ath



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THE MAR-HALL TE-T

AIM0

"o measure the resistance to plastic flow of cylindrical specimens

6!ri&uettes7 of !ituminous paving mi)tures loaded on the lateral

surface !y means of the Marshall apparatus. "he !ulk relative density

of the compacted Marshall !ri&uettes will also !e measured.

THEORY

"he Ma(!%all Mix #e!i"nprocedure is pro!a!ly the most widely used

method of !ituminous mi) design. t is governed !y (S"M ;DDolder

oading 'ack

>ot +late or oven

ompaction >ammer

"rowel

>eat #esistant Gloves



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"hermometers

Balance

>ot Water Bath

Flow Meter

Filter *iscs

Scoop

Small metal containers

Specimen mould holder

Breaking head

MATERIAL

Blen#e# &*a(!e a""(e"ae

Fine A""(e"ae

Fille(

Bi)men

PROCED1RE0

;. (ggregates were first sieved and weighed out to attain the

re&uire variations in si0e for the mi).

A. (ggregates$ filler and the mold were then placed in the oven

and left to dry for 23 %*)(!at 456*C * 445*C,



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. (ll essential mi)ing e&uipment that would come in contact

with either the asphalt cement$ ($ or the su!se&uent

asphaltic concrete mi) was placed on the hot plate and

!rought to a operating temperature *+ 78*& * 437*C.

. =sing a pre,determined ( content of .D$ the Mass of (

needed was calculated.

D. "he aggregates were then removed from the oven and place

within a mi)ing !owl and dry mi)ed thoroughly. (fter the

aggregates were thoroughly mi)ed$ they were placed on the

!alance and the pre,determined &uantity of !itumen was

poured 6as descri!ed in step D7.

3. "he mi)ing !owl was transferred to the hotplate and the dry

mi)? !itumen was !lended$ avoiding spillage$ until aggregate

thoroughly coated with !itumen.

H 8ote Steps I J must !e e)ecuted &uickly$ accurately and cautiously

to minimi0e heat loss and avoid injury at all cost !y wearing the right

protective apparel.

J. "he mold was taken from the oven and placed on the

compaction pedestal 6a filter paper disc was placed in the

!ottom of the mold7 and the !lend transferred into it. (fter

the entire !atch was placed in the mold it was spaded



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vigorously with a heated knife$ ;D times around the perimeter

and ;1 times over the interior.

2. "he !lended components were pored unto a filter paper disc

placed within the compacted mold$ and with the compaction

hammer held as near to vertical as possi!le$ D1 !lows were

applied to the top of thespecimen.


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the specimen. "he reading was then recorded and the

!ri&uette sent to disposal.

RE-1LT- AND CALC1LATION0

Ma!! *+ a""(e"ae )!e# * *baine# Ma(!%all B(i9)ee:



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;Table 4,5eight 6mm7 33.J1 3D.11 3D.A1 3D.11 (verage K3D.D1

;, Mass of asphalt cement to produce ( content of D.D

( content D.D K Mass of ( ) ;11 Mass of ( L"otal mass of aggregate

( content D.D K Mass of ( ) ;11 Mass of ( L ;;


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;Table 4,4

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