A Presentation onEXPERIMENTAL STUDIES

ON NANOCLAY MODIFIED

BITUMINOUS MIXES

SHAIK FARHEEN SULTANA

160313741401

CONTENTS INTRODUCTION

LITERATURE REVIEW

RESEARCH GAP

RESEARCH OBJECTIVE

RESEARCH SCOPE

MATERIALS AND METHODS

RESEARCH OUTCOMES AND SIGNIFICANCES

INTRODUCTION Bitumen used as a binder for road paving applications is a

form of liquid at high temperature and become brittle at low temperatures which can cause high temperature rutting ,low temperature cracking of the pavement and limits its applications .

About 98 percent of paved roads in India have flexible pavements which have surfacing of Bituminous mixes with different thicknesses.

Physical properties and temperature susceptibility characteristics of the bitumen influence pavement stiffness, both at high and low field-operating temperatures, and thereby can affect final performance of the mixture

INTRODUCTION Pavement distresses such as rutting at high temperatures can be

reduced by using modified bitumen.Addition of polymers to

bitumen is known to impart enhanced service properties such

as improved thermo mechanical resistance, elasticity and

adhesivity. But polymer modified bitumens are expensive,

difficult for operation and incompatible.Therefore further

efforts should be made for exploring new modifiers.

Montmorillonite modified bitumen composition have been

successfully used to improve both physical and rheological

property of bitumen. It has exhibited a decreasing

penentration,an increasing softening point, a decreasing

ductility properties.

INTRODUCTION

Most of roads develop distress like raveling, undulations,

rutting,cracking,bleeding,shoving of bituminous surfacing.

Pavement performance is determined by properties of bitumen

as bitumen is a continuous phase,only deformable component ,

binding material and protective coating which plays a key role

in performance related properties of bituminous mix.

Low temperature in winter can stiffen the binder and reduce the

flexibility of paved mix resulting in cracking and other

distresses.

Hence modification may be necessary for better performing

bituminous mix and to solve the problem of premature failure

to some extent.

LITERATURE REVIEW Daniel Beyene Ghile,2006: Two types of nanoclay modifications were

studied ;nanofill and cloisite the study work was to conduct a comparative

test program on binders containing standard and nanoclay modified asphalts

and assess the effects of asphalt properties on pavement performances

Lamya M. J. Mahdi1, Ratnasamy Muniandy1, Robiah Bt. Yunus2,

Salihudin Hasham1, Eltaher Aburkaba1,2013:

Two types of organic montmorillonite nanoclay (N3 and N4) were chosen

to blend with 80/100 base asphalt in various concentrations (3%, 7% and

9%) by weight of the asphalt and subjected to aging using the Rolling Thin

Film Oven in order to simulate short term aging.

H.L.ZHAANG.J.Y.YU,L.H.XUE AND Z.L.LI,2011:Effect of

montmorillonite organic modification on microstructures and ultraviolet

aging properties of bitumen was investigated by characterising the micro

structures of MMT modified bitumen by X-ray diffraction(XRD),Fourier

transform infrared spectroscopy and atomic force microscopy.

LITERATURE REVIEW D.B.Ghile,A.A.A Molinaar,M.F.C Van De Ven,J.Besamusca:Nano

technology applied in bitumen to improve asphalt mix behavior.This paper

reported the change in rheological properties due to addition of nano clay

which helped in reducing the phase angle,increasing stiffness and reducing

the ageing of bitumen at some extent.

S.Ghaffarpour Jahromi,N.A Ahmadi,SM Mortazavi and S Vossough,2011;

Rutting and fatigue behavior of nanoclay modified bitumen.The objective of

this study was to evaluate the conventional and rheological properties of

binders containing various percentages of organic montmorillonite nanoclay

particles before and after a short-term aging process.

Gang LIU,2011:Characterization and identification of Bituminous

materials modified with montmorillonite nanoclay .

RESEARCH OBJECTIVE

The main objective of the study work is to conduct a

comparative test program on bitumen and bituminous mixes

and to evaluate the effects of montmorillonite on performance

of bituminous mixes containing standard and nano modified

bitumen.

The specific objectives of the study are:

Study the nanoclay modifiers at nanoscale level.

To determine the optimum dosage of montmorillonite

Investigate and evaluate the role of different percentages of

montmorillonite modifiers in changing the rheological

properties of bitumens.

Study the effect of the nanoclay modifiers on ageing

effect of the binder

To compare the performance of montmorillonite-modified

mixes with that of plain bituminous mixes.

RESEARCH SCOPE

The study comprises of nanoclay modifiers (montmorillonite)

on two types of binders (40/60, 70/100). The proportions of the

nanoclay modifiers considered in the study work are 3% and

6% in relation to the weight of the binder. Taking into account

the different test types performed, the different types and

proportions of modifiers and the different mixture types, the

overall study work done is broad and versatile.

METHODOLOGYThe experimental methodology consist of the following four essential phases.

Phase I: Material Collection

Aggregate: crushed Granite coarse and fine aggregate were from collected

from quarry.

Binder: Plain bitumen of viscosity grade 30 (VG30).

Modifier or additive: Montmorillonite produced by market.

Phase II: Material Characterization

Standard test such as Aggregate Crushing Strength, Impact value, Stripping

value, Los Angeles Abrasion value, Specific gravity and Combined

Elongation and Flakiness tests to characterise the aggregates.

Standard tests such as Penetration, Softening point, Specific gravity,

Ductility and Viscosity tests to characterise the bitumen.

Phase III: Preparation of test specimens

Standard Marshall Specimens.

Compaction using standard and modified hammer.

No of blows 75 on either side.

Phase IV: Performance Testing

Marshall Test to assess strength of different bituminous mixes.

Indirect Tensile Strength of conditioned and unconditioned

specimens to evaluate the rutting potential and moisture

susceptibility.

In this study work two phases of experimental tests are

performed and reported

In this study work two phases of experimental tests are performed

and reported.

The first phase of the study work comprises analysis of rheological

properties of the modified binder in relation to standard binder.

The tests performed include

1. X-ray and microscopic analyses of the nanoclay

modifiers(montmorillonite)

2. Empirical rheological analysis (penetration, softening

point,ductillity test,specific gravity test)

3. Fundamental rheological properties measured with the

dynamic shear rheometer (DSR).

The second phase comprises comparative tests and analyses

between modified mix and standard dense mix.

The tests performed in this phase are indirect tensile

1. strength tests at five temperature values, dynamic stiffness

tests at different temperature values

2. Fatigue resistance tests at different temperature values and

deformation at three different temperatures and three different

loading values.

FIRST PHASEX-ray analysis:

X-ray analysis was performed for two main purposes being:

• 1. To know the elemental composition of the nanoclay materials

• 2. To know the chemical composition and if possible the chemical formula of the basic molecules of the nanoclay materials

• a. Qualitative wavelength dispersive spot analyses: This test was performed to get a qualitative analysis about the elemental composition of the nanoclay modifiers.

• b. X-ray diffraction: This test was performed to get the chemical composition of the compounds of the nanoclay. This is done by determining the crystal shape of the nanoclay compounds through the test and correlating them with close match compounds from the library.

First Phase work

MICROSCOPIC ANALYSIS

• This test was performed to get insight on the size,

shape,arrangement and interaction of the particles of the

nanoclay modifiers at nanoscale level. The analysis was

done using an electron microprobe

Plastic analysis:• To get an idea on the consistency of the nanoclay materials a

plastic limit test was performed on both materials

RHEOLOGICAL TESTS

The rheological tests done are of two types:

i. Empirical rheological tests: These comprise the penetration

test and softening point test,ductility test

ii. Fundamental rheological tests: These comprise tests with the

DSR, Rotating Cylindrical Ageing Tester (RCAT),PAV.

iii.And then it is followed by penetration and softening point

computations by comparing modified and standard bitumen.

EMPERICAL RHEOLOGICAL TESTSPENETRATION TEST

• Penetration tests determines the hardness or softness of bitumen by

measuring the depth in tenths of a millimeter to which a standard loaded

needle will penetrate vertically in five seconds at a temperature of 25°C.

• The penetration test determines the consistency of bitumen for purpose of

grading. The softer the bitumen, the greater will be the penetration value.

SOFTENING POINT TEST

The softening point is the temperature at which the substance attains

particular degree of softening under specified condition of test.

Generally higher softening point indicates lower temperature susceptibility

and is preferred in warm climates. Hard grade bitumen possesses higher

softening point than soft grade bitumen

DUCTILITY TEST

Ductility test gives a measure of adhesive property of bitumen

and its ability to stretch.

As the binders form ductile thin films around the aggregates, a

certain minimum ductility is necessary for a binder to

withstand the temperature changes in mixes and the repeated

deformations that occur due to the traffic loads.

DSRThe discussion on DSR test results comprises the following areas:

A typical DSR test results analysis which comprises :

frequency sweep analysis;

master curve and black diagram.

Comparison of the master curves of the stiffness of the modified and unmodified binders.

Comparison of the master curves of phase angles of the modified and unmodified binders.

Analysis of the change in ageing effect of the binder due to the modification.

Analysis of the rutting and fatigue resistance parameters for the modified and unmodified binders.

Frequency sweep DSR test results

The frequency sweep results can be used in the construction of master curves and black diagrams

Master curve of stiffness and phase angle Construction of mater curves of stiffness and phase angle is of great

significance because:

it can describe rheological properties of bitumen under a wide range of loading frequencies for a selected temperature value;

a comparison of stiffness and phase angle values of the modified and unmodified binders is better described by master curve values than frequency sweep results;

an effect of modification on the ageing effect of the binder can also be better explained and clarified using master curve values than the frequency sweep results.

BLACK DIAGRAM

The black diagram relates the complex modulus with the phase

angle value and is unique for a selected binder type. The black

diagram is seen as a fingerprint of the binder. It can tell us how

the two values are related under wide temperature ranges

SHORT TERM AGEING EFFECT ANALYSIS

The short term ageing effect analysis is performed based on the

master curves of the stiffness and phase angle values

PREPARATION OF SPECIMENCHARACTERIZATION OF AGGREGATES

In order to access the suitability of the aggregate for road

construction, the mechanical and physical properties of

aggregates are tested in laboratory.

Crushing value

los angles abrasion value,

impact value,

specific gravity of course and fine aggregate,

combined elongation and flakiness index

MARSHALL STABILITY TEST

The Marshall stability of the mix is defined as the maximum

load carried by the specimen at a standard test temperature of

60 degree Celsius the temperature which represents the

weakest condition for a bituminous pavement in use.

The steps involved in this test are

• Mixing

• Compaction

• Mix properties

MIXING PROCESS

The coarse and fine aggregate were taken in the specified

proportions so as to produce compacted bituminous mix specimens

of thickness 63.5mm approximately and the weighed quantity of

bitumen corresponding to each percentage was added to the heated

aggregate and thoroughly mixed at the specified mixing temperature,

using a mechanical mixer.

COMPACTION METHOD

To evaluate the effect of compaction on mix properties two types of

compaction methods were adopted. Standard Marshall Compaction

and modified Marshall Compaction efforts were analyzed by

comparing the volumetric properties and performance parameters of

mixes prepared with different types of compaction hammers

MIXING PROPERTIES

The important properties of the mix are

theoretical specific gravity(Gt)

the bulk specific gravity of the mix(Gm)

percent air voids(Vv)

percent volume of bitumen(Vb)

percent voids in mineral aggregate(VMA) and

percent voids filled with bitumen(VFB)

SECOND PHASE

Tests are to be performed on modified and standard dense

bituminous mixtures and the comparison of the test results to

see the effect of the clay modification on the performance of

the asphalt mixtures.

The performance tests selected for comparison are:

i. Indirect tensile strength test

ii. Resilient modulus test

iii. Dynamic creep test

iv. Fatigue resistance test

DYNAMIC CREEP TEST

Dynamic creep test is performed to:

determine the resistance to permanent deformation of the standard and modified dense mixtures at high temperatures and make a comparative analysis;

investigate the effect of variation of temperature and level of applied pressure on the permanent deformation resistance response of the modified and standard dense mixes.

INDIRECT TENSILE STRENGTH discusses on:

Test result analysis and comparison of indirect tensile strength values of the modified and unmodified dense asphalt mixtures;

comparison of the fracture energy of the modified and unmodified asphalt mixtures

RESILIENT MODULUS TEST

The resilient modulus test is performed to :

Determine the elastic moduli of the modified and standard dense mixtures and develop master curves for each mix;

Make a comparative analysis of resilient modulus values between the standard and modified dense mixtures.

FATIGUS RESISTANCE TEST

Fatigue resistance test is performed to determine the fatigue resistance of the standard and modified dense mixtures at different test temperatures and loading conditions and

to make a comparative analysis of their fatigue resistance.

MODELS USED IN THE STUDY ARE

Using regression analysis, fatigue equations were developed.

The linear regression models of fatigue life (Nf) with resilient

modulus (Mr) are developed and Linear Regression equation

between Fatigue life (Nf) and Initial strain (Ɛ)

ANOVA analysis was done between the fatigue life of the

control with nano-modified mixes at 5% binder content for

VG30. The null hypothesis is their means are equal and the

alternative hypothesis is their means are not equal.

OUTCOME• From the previous studies Tests performed on binders and

dense asphalt mixtures proved that the nanoclay modifications helped to increase the stiffness, to improve the rutting resistance of the standard 40/60 binder.

In addition, the indirect tensile strength and fracture energy values are increased due to modification.

The nanofill modification helps to improve the ageing resistance of the 70/100 binder in the short term and long term too.

However, when it comes to fatigue resistance performance, the standard binders/mixtures were performing better than the nanoclay modified binders /mixtures especially at low test temperatures.

REFERENCES ASTM D5581 (1996). “Resistance to plastic flow of bituminous mixes

using Marshall Apparatus”.

ASTM D6931 (2007). “Standard Test Method for Indirect Tensile (IDT)

Strength of Bituminous Mixes

Fundamental Characterization of Asphalt Clay Nano-Composites

Dr. John Read and Mr. David Whiteoak, 2003, The Shell Bitumen Hand

book, UK

NCHRP report 459, 2001, characterization of modified asphalt binders in

superpave mix design, Washington D.C.

TRB report number 1454, 1994, Asphalt concrete mixture design and

performance,Washington D.C.

TRB report number 1590, 1997, Asphalt mixture quality characteristics and

performance, Washington D.C.

REFERENCES TRB report number 1789, 2002, bituminous paving mixtures materials and

construction,Washington D.C.

TRB report number 1832, 2003, bituminous paving mixtures, Washington

D.C.

TRB report number 1488, 1995, unmodified and modified asphalt binders,

WashingtonD.C

D.B Ghile, A.A.A. Molenaar, M.F.C. van de ven, J. Besamusca, CROW

conference WW2006, Nanotechnology applied to bitumen to improve

asphalt mixture behavior Doorwerth, The Netherlands

Prf.dr.A.A.A. Molenaar, D.B Ghile, Ir.M.F.C. van de ven ,December 2005,

report number 7-04-110-25, CROW report, Effect of nano-clay modification

on rheology of bitumen ,The Netherlands