CE 2020: Construction Materials Dr. B. Munwar Basha IIT Hyderabad Bituminous Materials.

CE 2020: Construction Materials Dr. B. Munwar Basha IIT Hyderabad

Bituminous Materials

CE 2020: Construction Materials Dr. B. Munwar Basha IIT Hyderabad 2

PETROLEUM AND PRODUCTION

Petrolem = Petra + Oleum Rock + Oil

Petroleum is often called crude oil, fossil fuel or oil.

It is called a fossil fuel because it was formed from the remains of tiny sea plants and animals that died millions of years ago.

When the plants and animals died, they sank to the bottom of the oceans.

Here, they were buried by thousands of kms of sand and sediment, which turned into sedimentary rock.

As the layers increased, they pressed harder and harder on the decayed remains at the bottom.

The heat and pressure changed the remains and, eventually, petroleum was formed.


How coal formed

Over millions of years, due to high temperatures and pressure…

the trees became fossilized, forming coal.

Millions of years ago trees died and fell to the bottom of swamps.

Over time they became covered by mud and rock.


How oil and natural gas formed


Where We Get Oil?

The world's top five crude oil-producing countries are: Saudi Arabia Russia United States Iran China


Concentration of Oil

Structural Traps Fault Anticline Salt dome

http://www.priweb.org/ed/pgws/systems/traps/traps_home.html


Concentration of Oil


1. Boiling point2. Density3. Odour4. Viscosity

Light-heavy : Low boiling point and relative density

Heavy-heavy : High boiling point, viscous.

Because crude oil has Fe, Mg, Ca, P, V, S, Zn, Co, clay, water and other residuals, it has to distillate for internal combustion engines.

Petroleum is defined by 4 physical categories historically


1 World 85.220.000

2 United States 20.680.000

3 European Union

14.380.000

4 China 7.880.000

5 Japan 5.007.000

6 India 2.722.000

7 Russia 2.699.000

8 Germany 2.456.000

9 Brazil 2.372.000

10 Canada 2.371.000

11 Mexico 2.119.000

12 Korea, South 2.080.000

13 France 1.950.000

14 United King

dom

1.763.000

15 Italy 1.702.00

0

16 Spain 1.611.00

0

17 Iran 1.600.00

0

18 Indonesia 1.564.00

0

19 Saudi Arabi

a

1.000.000

20 Netherlands 984.200

26 Turkey 676.600

2009 Oil consumption bbl/day

http://www.theodora.com/wfbcurrent/world/world_economy.html

http://www.theodora.com/wfbcurrent/united_states/united_states_economy.html

http://www.theodora.com/wfbcurrent/european_union/european_union_economy.html

http://www.theodora.com/wfbcurrent/european_union/european_union_economy.html

http://www.theodora.com/wfbcurrent/china/china_economy.html

http://www.theodora.com/wfbcurrent/japan/japan_economy.html

http://www.theodora.com/wfbcurrent/india/india_economy.html

http://www.theodora.com/wfbcurrent/russia/russia_economy.html

http://www.theodora.com/wfbcurrent/germany/germany_economy.html

http://www.theodora.com/wfbcurrent/brazil/brazil_economy.html

http://www.theodora.com/wfbcurrent/canada/canada_economy.html

http://www.theodora.com/wfbcurrent/mexico/mexico_economy.html

http://www.theodora.com/wfbcurrent/korea_south/korea_south_economy.html

http://www.theodora.com/wfbcurrent/france/france_economy.html

http://www.theodora.com/wfbcurrent/united_kingdom/united_kingdom_economy.html

http://www.theodora.com/wfbcurrent/united_kingdom/united_kingdom_economy.html

http://www.theodora.com/wfbcurrent/italy/italy_economy.html

http://www.theodora.com/wfbcurrent/spain/spain_economy.html

http://www.theodora.com/wfbcurrent/iran/iran_economy.html

http://www.theodora.com/wfbcurrent/indonesia/indonesia_economy.html

http://www.theodora.com/wfbcurrent/saudi_arabia/saudi_arabia_economy.html

http://www.theodora.com/wfbcurrent/saudi_arabia/saudi_arabia_economy.html

http://www.theodora.com/wfbcurrent/netherlands/netherlands_economy.html

http://www.theodora.com/wfbcurrent/turkey/turkey_economy.html


Crude oil is a mixture. It contains hundreds of different

compounds. Some are small but most are large. Nearly all of these compounds contain

carbon and hydrogen only. They are called hydrocarbons. Also some other compounds contain small

amounts of N and S. Why?

Hydrocarbons are molecules that contain carbon and hydrogen only.

Crude Oil


Element

Percent range

Carbon 83 to 87%

Hydrogen

10 to 14%

Nitrogen

0.1 to 2%

Oxygen0.05 to 1.5%

Sulfur0.05 to 6.0%

Metals < 0.1%

Composition by weight

Hydrocarbon

Average

Range

Paraffins 30%15 to 60%

Naphthenes 49%30 to 60%

Aromatics 15% 3 to 30%

Asphaltics 6%remainder


Oil Refining

Typical Oil Gasoline C4 to C10 27% Kerosene C11 to C13 13% Diesel C14 to C18 12% Heavy gas oil C19 to C25 10% Lubricating oil C26-C40 20% Residue >C40 18%


The hydrocarbons in crude oil are essential to our way of life

We use them as fuels for most forms of transport.

We also use them as raw materials from

which a HUGE range of useful everyday substances are made

The importance of oil


Crude oil is a mixture of hydrocarbons with a VERY wide range of sizes.

Crude oil itself has no uses because its properties are not definite.

To make crude oil into useful substances we have to separate the mixture into molecules of similar size.

This is done in an oil refinery in a process called fractional distillation.

The physical property used to separate the fractions is boiling point.

Making Oil Useful


Oil drilling occurs both at sea and on land, depending on the size and profitability of the oil deposits located.

The first step is the transport of the crude oil from its natural location to the refinery.

Once obtained from the ground, the oil is transported by ship, truck or pipeline to the refinery.

From the Field to the Refinery

Extraction process of crude oil from the Sea


Oil Rig from air


• To separate it into useful products begins.

• Have complex stages and each part have several processes.

• The very first step is to break up the crude oil.

Fractional Distillation Of Crude Oil


Distillation Distillation separates chemicals by the

difference in how easily they vaporize. The two major types of classical distillation

include continuous distillation and batch distillation.

Continuous distillation, as the name says, continuously takes a feed and separates it into two or more products.

Batch distillation takes on lot (or batch) at a time of feed and splits it into products by selectively removing the more volatile fractions over time.

Many industries use distillation for critical separations in making useful products. These industries include petroleum refining, beverages, chemical processing, petrochemicals, and natural gas processing.


Fractional distillation of crude oil is the first step in the production of many of the materials we have come to rely on in modern life.

All our fossil fuels, virtually all our plastics, detergents and commercial alcohols are made from products of this process.

In order to separate the different length chains in the crude mix, it is heated to a very high temperature.

The temperature cannot be set higher than this as there is a risk that the lighter fractions will ignite.



Distillation is the most common form of separation technology used in petroleum refineries, petrochemical and chemical plants, natural gas processing.

Industrial distillation is typically performed in large, vertical cylindrical columns known as "distillation or fractionation towers" or "distillation columns" with diameters ranging from about 65 centimetres to 6 metres and heights ranging from about 6 metres to 60 metres or more.

The distillation towers have liquid outlets at intervals up the column which allow for the withdrawal of different fractions or products having different boiling points or boiling ranges.

By increasing the temperature of the product inside the columns, the different hydrocarbons are separated.

The "lightest" products (those with the lowest boiling point) exit from the top of the columns and the "heaviest" products (those with the highest boiling point) exit from the bottom of the column.



Industrial Distillation Of Crude Oil


Fractional Distillation


27

Major products of oil refineries1.Liquid petroleum gas

(LPG)2.Gasoline (also known as

petrol)3.Naphtha4.Kerosene and related jet

aircraft fuels5.Diesel fuel6.Fuel oils7.Lubricating oils8.Asphalt and Tar9.Petroleum coke


Fractional distillation is used in oil refineries to separate crude oil into useful substances (or fractions) having different hydrocarbons of different boiling points

Major products of oil refineries


Asphalt

The products refined from the liquid fractions of crude oil can be placed into ten main categories Asphalt

Asphalt is commonly used to make roads. It is a colloid of asphaltenes and maltenes that is separated

from the other components of crude oil by fractional distillation.

Once asphalt is collected, it is processed in a de-asphalting unit, and then goes through a process called “blowing” where it is reacted with oxygen to make it harden.

Asphalt is usually stored and transported at around 150 C.


Diesel

Diesel is any fuel that can be used in a diesel engine. Diesel is produced by fractional distillation between 250° Fahrenheit and 350° Fahrenheit. Diesel has a higher density than gasoline and is simpler to refine from crude oil. It is most commonly used in transportation. Fuel Oil Fuel oil is any liquid petroleum product that is burned in a furnace to generate heat.Fuel oil is also the heaviest commercial fuel that is produced from crude oil.

Diesel and Fuel Oil


GASOLINE Gasoline is an extremely flammable

fuel source for automobiles and other vehicles and equipment.

A liquid, it can be colorless, pale brown or pale pink.

Gasoline is not a single substance.

There is no such thing as pure gasoline.

Gasoline is produced by refining petroleum, and it consists of a complex mixture of over 120 hydrocarbons.


Gasoline

It is mainly used as fuel in internal combustion engines, like the engines in cars.

Gasoline is a mixture of paraffins, naphthenes, and olefins, although the specific ratios of these parts depends on the refinery where the crude oil is processed.

Gasoline refined beyond fractional distillation is often enhanced with iso-octane and ethanol so that it is usable in cars.

Gasoline is called different things in different parts of the world.

Some of these names are: petrol, petroleum spirit, gas, petrogasoline, and mogas.

Kerosene

Kerosene is collected through fractional distillation at temperatures between 150° Fahrenheit and 275° Fahrenheit. It is a combustible liquid that is thin and clear. Kerosene is most commonly used as jet fuel and as heating fuel.

Gasoline and Kerosene


36

Liquefied Petroleum Gas

Liquefied petroleum gas is a mixture of gases that are most often used in heating appliances, aerosol propellants, and refrigerants.

Different kinds of liquefied petroleum gas, or LPG, are propane and butane.

At normal atmospheric pressure, liquefied petroleum gas will evaporate, so it needs to be contained in pressurized steel bottles.

Lubricating Oil

Lubricating oils consist of base oils and additives. Different lubricating oils are classified as paraffinic,

naphthenic, or aromatic. Lubricating oils are used between two surfaces to reduce friction and wear.

The most commonly-known lubricating oil is motor oil, which protects moving parts inside an internal combustion engine.

Liquefied Petroleum Gas and Kerosene


Paraffin Wax Paraffin wax is a white, odorless, tasteless, waxy solid at

room temperature. The melting point of paraffin wax is between 47° C and 65°

C, depending on other factors. It is an excellent electrical insulator, second only to Teflon®,

a specialized product of petroleum. Paraffin wax is used in drywall to insulate buildings. It is

also an acceptable wax used to make candles.

Bitumen Bitumen, commonly known as tar, is a thick, black, sticky

material. Refined bitumen is the bottom fraction obtained by the

fractional distillation of crude oil. This means that the boiling point of bitumen is very high, so

it does not rise in the distillation chamber. The boiling point of bitumen is 525° C.

Bitumen is used in paving roads and waterproofing roofs and boats. Bitumen is also made into thin plates and used to sound proof dish washers and hard drives in computers.

Paraffin Wax and Bitumen


Why do these fractions condense over a boiling range?Fraction Boiling Range (oC)

Fuel gas Below 40

Petrol 40 - 175

Kerosene 150 - 240

Diesel 220 – 275

Lubricating oil 250-350

Bitumen >350

cool

hot

Fuel gas

Petroleum

Kerosene

Diesel

Lub. Oil

Bitumen

Fractional Distillation


Fuel gas

Petrol / gasoline

Naphtha

Paraffin / Kerosine

Diesel fuel

Fuel and lubricating oil

Bitumen

Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gas

Fuel for cars and motorcycles, also used to make chemicals.

Used to make chemicals used everwhere.

Fuel for green house heaters and jet engines, manufacture of chemicals.

Fuel for lorries and trains.

Fuel for the heating systems of large buildings, fuel for ships, lubricating oil.

Roofing, and road surfaces.

Uses of each fraction


In general, the bigger the molecule the higher the boiling point.

0

50

100

150

200

250

300

350

0 5 10 15 20

No. Carbon atoms

B.Pt

(oC)

The boiling points of molecules


Here are the boiling ranges of some fractions obtained from distillation of petroleum.

Fraction Boiling Range

(oC)

Number of carbons

Fuel gas Below 40Petrol 40 - 175Kerosine 150 - 240Diesel 220 - 275

1-5

5-109-1413-

17

boiling ranges


What is Bitumen? In North America, bitumen is commonly

known as “asphalt cement” or “asphalt binder.”

Asphalt pavement is a mixture of about 5 percent bitumen (asphalt cement) and 95 percent small stones, sand, and gravel.

Bitumen (asphalt cement) is produced by distillation of crude oil during petroleum refining.

It also occurs naturally. Bitumen can be divided into broad

categories based on physical properties and specifications for different uses. Straight-run bitumen is used in paving Oxidized bitumen is used in roofing

42


Coal is a fossil fuel mined from ancient deposits.

It is a black mineral of plant origin which is chemically, a complex mixture of elemental carbon, compounds of carbon containing hydrogen, oxygen, nitrogen and sulphur.

Coal is believed to have been formed about 300 million years ago under the Earth by a process called carbonization.

Carbonization is the process of slow conversion of vegetable matter to coal under the Earth due to the action of high pressure, high temperature, anaerobic bacteria and absence of oxygen.

What is Coal Tar?


Formation of coal in flow diagram


Types of coal

Depending upon the extent of carbonization, coal can be classified into four types as follows:

Classification of coal Peat 11% , Lignite 38% (Soft coal / brown coal) Bituminous 65% (Household coal) Anthracite 96% (Hard coal)

Peat is the first stage in the conversion of vegetable matter to coal while anthracite is the last.


Distillation or Destructive distillation of coal ?

The process of heating coal in the absence of oxygen to obtain useful products is called destructive distillation of coal


Product Formed/collected in Uses

Coal Tar (complex mixture of carbon compounds)

Bottom of the test tube B. Liquid residue insoluble in water

Can be distilled to obtain: Benzene — solvent Toluene — manufacture of explosive TNT Naphthalene — insect repellent

Coal gas (CH4+CO+H2)

Combustible gas insoluble in water. Escapes through the side tube

Industrial fuel

Liquor ammonia (NH4OH)

Soluble in water present in test tube

Manufacture of nitrogenous fertilizers

Coke (98%C) Solid residue left behind in test tube A

i) Reducing agent in metallurgy ii) Manufacture of water gas and producer gas — Industrial fuel

Products formed and their uses


8

Comparison between Asphalt and TarSIMILARITIES:

1. Composed principally of Bitumen.2. Black or dark brown in color.3. Cementitious.4. Water repellent.

DIFFERENCES:1. Distinguished by odor (tar has an aromatic odor).2. The insoluble portion in natural asphalt is mineral matter,

while the insoluble in tar is free carbon.3. Tar molecules tend to be aromatic (ring or cyclic), while

asphalt molecules tend to be aliphatic (straight chain)4. Tar is more temperature susceptible5. Tar can coat aggregates better and is more water

resistant.6. Asphalt is more weather resistant.7. Asphalt can occur in natural form or come as a by-product

of petroleum refinery. Tar does not occur in natural form, but comes as a by-product in the manufacture of coke or water-gas.

8. Fumes from heated tar cause health hazards such as severe eye and skin irritation.


9

Bituminous

Tar

Comparison between Asphalt and Tar


0

The composition of bitumen Bitumen is a complex combination of hydrocarbons with small

quantities of sulphur, oxygen, nitrogen and trace quantities of metals such as vanadium, nickel, iron, magnesium and calcium.

Crude oils normally contain small quantities of polycyclic aromatic hydrocarbons (PAHs), a portion of which end up in bitumen.

Although some of these PAHs are suspected of causing cancer in humans, the concentrations are extremely low and no causal link to cancer in humans has been established.

Most bitumens manufactured from a range of crude oils contain:

Carbon 82 - 88%Hydrogen 8 - 11%Sulphur 0 - 6%Oxygen 0 - 1.5%Nitrogen 0 - 1%


1

Broad chemical components of bitumen It is convenient to separate bitumen into two broad chemical

groups, called asphaltenes and maltenes Maltenes are further subdivided into saturates, aromatics and

resins


2

Asphaltenes Asphaltenes are fairly high molecular weight, n-

heptane insoluble solids that are black and glassy. They make up 5 - 25% of the bitumen, and contain

carbon, hydrogen, some nitrogen, sulphur and oxygen.

The asphaltenes content has a significant influence on the rheological properties of the bitumen.

Increasing the asphaltenes content produces a harder, more viscous binder.


3

Resins Resins are largely composed of hydrogen and

carbon, with small amounts of oxygen, sulphur and nitrogen, making up 30 - 50% of the total bitumen.

These dark brown solids or semi-solids act as a dispersing (peptising) agent for the asphaltenes.

Being polar in nature, they are strongly adhesive. The properties of resins characterise to a degree the

type of bitumen, i.e. "solution" (SOL) or "gelatinous" (GEL) (see Bitumen structure.)


4

Aromatics Aromatics are dark brown, low molecular weight,

viscous fluids making up 40 - 65% of the total bitumen, and the ability to dissolve other, high molecular weight hydrocarbons.

The aromatic content of the bitumen determines to a significant extent its compatibility with polymers used for modification.


5

Saturates

Saturates are straw coloured or white, viscous oils with a molecular weight similar to that of aromatics.

They contain both waxy and non-waxy saturates and make up 5 - 20% of the bitumen.


A fluid is defined as a material which will continue to deform with the application of a shear force. However, different fluids deform at different rates when the same shear stress (force/area) is applied.

Viscosity is that property of a real fluid by virtue of which it offers resistance to shear force.

For a given fluid the force required varies directly as the rate of deformation. As the rate of deformation increases the force required also increases.

The force required to cause the same rate of movement depends on the nature of the fluid.

The resistance offered for the same rate of deformation varies directly as the viscosity of the fluid.

As viscosity increases the force required to cause the same rate of deformation increases.

Viscosity of Fluids


,F

StressA

dShear Rate

dt

h

L

ForceArea

LStrain

h

Viscosity of Fluids


Dynamic Viscosity

1 centi-Poise = milli Pascal-second

SI Unit: Pascal-second

Shear stress

Shear rate

Slope of line

Newton’s law of viscosity states that the shear force to be applied for a deformation rate of (du/dy) over an area A is given by,

where F is the applied force in N, A is area in m2, du/dy is the velocity gradient (or rate of deformation), 1/s, perpendicular to flow direction, here assumed linear, and μ is the proportionality constant defined as the dynamic or absolute viscosity of the fluid.


Dynamic Viscosity The dimensions for dynamic viscosity μ can be

obtained from the definition as Ns/m2 or kg/ms. The first dimension set is more advantageously

used in engineering problems. However, if the dimension of N is substituted, then

the second dimension set, more popularly used by scientists can be obtained.

The numerical value in both cases will be the same.

N = kg m/s2 ; μ = (kg m/s2) (s/m2) = kg/m/sThe popular unit for viscosity is Poise named in

honour Poise = 0.1 Ns/m2

Centipoise (cP) is also used more frequently as,

cP = 0.001 Ns/m2


Kinematic Viscosity The ratio of dynamic viscosity to the density is

defined as kinematic viscosity, ν, having a dimension of m2/s.

Later it will be seen to relate to momentum transfer.

Because of this kinematic viscosity is also called momentum diffusivity.

The popular unit used is stokes (in honour of the scientist Stokes).

Centistoke is also often used.1 stoke = 1 cm2/s = 10–4 m2/sof all the fluid properties, viscosity plays a very important role in fluid flow problems.The velocity distribution in flow, the flow resistance etc. are directly controlled by viscosity.


Typical Viscosities (Pa.s)

Asphalt Binder --------------- Polymer Melt ----------------- Molasses ---------------------- Liquid Honey ----------------- Glycerol ----------------------- Olive Oil ----------------------- Water -------------------------- Acetic Acid --------------------

100,0001,0001001010.010.0010.00001

Courtesy: TA Instruments


Newtonian Fluids

Shear stress

Shear rate

Examples:

• Water

• Milk

• Vegetable oils

• Fruit juices

• Sugar and salt solutions

• Fluids of the most commonly encountered in fluid engineering are water and air, and also, include structurally simple fluids with low molecular weight, are found to obey “Newton’s law of viscosity”.

• Such fluids are referred to as Newtonian fluids.

• The Newton’s law of viscosity states that the shearing force is proportional to the shear rates


Different types of Fluids

Shear stress

Shear rate

Newtonian

Pseudoplasti

c (or S

hear

thinning)

Dilata

nt (or S

hear

thick

ening)

Bingham PlasticCass

on Plastic

Non Newtonian Fluids


Non-Newtonian Foods In a general sense, fluids that exhibit characters not

predicted by the Newtonian constitutive equation (linear) are non-Newtonian.

The exceptions to the Newtonian fluids are not of rare occurrence, and in fact many common fluids are non-Newtonian.

Some examples are: paints, solutions of various polymers and molten plastics; food products such as apple sauce, ketchup and other mammalian whole foods; synovial fluid found in joints, blood and other organic fluids; many solid-liquid and liquid-liquid suspensions such as fibers in a liquid paper pulp, coal slurries, emulsions of water in oil or oil in water, and so on.

The so-called non-Newtonian fluids, as mentioned above, are often found in many fields of engineering fluid mechanics as well as in bio-medical fields, and exhibit interesting, useful and even exciting characteristics differed from those found in Newtonian fluids.


5

Bitumen Structures The molecules in the bitumen further fall into two

functional categories - polar and non-polar molecules:1. Polar molecules form the network of the bitumen

and provide the elastic properties;2. Non-polar molecules provide the body of the

bitumen and its viscous properties. These two categories of molecules co-exist, forming

a homogeneous mixture. Their weak interaction results in the Newtonian

behaviour of bitumen at high temperatures, where the viscosity change is directly proportional to the temperature change.


6

"solution" type (SOL) bitumen In the presence of sufficient quantities of resins and

aromatics of adequate solvating capacity, the asphaltenes are fully dispersed, or peptised, and the resulting micelles have good mobility within the bitumen.

In such cases the bitumen is known as a "solution" type (SOL) bitumen as shown in Figure 6.


7

"solution" type (SOL) bitumen If the aromatic or resin fraction is not present in sufficient

quantities to peptise the micelles, or has insufficient solvating capacity, the micelles can associate together.

This leads to structures of linked micelles, and these types of bitumen are known as "gelatinous" (GEL) types and are depicted in the Figure.


8

Temperature Bitumen is a thermoplastic hydrocarbon

material which softens when heated and turns into a glassy state when cooled.

The following states generally describe the consistency of bitumen at various temperatures: At low road temperatures - a brittle solid; At room temperature - a sticky semi-solid; At high service temperatures - a

viscoelastic1 substance; At elevated temperatures - a viscous

liquid.


9

Viscoelastic properties Bitumen displays both elastic and viscous behaviour,

depending largely on temperature and load duration.

This viscoelastic character of bitumen results in its varied response behaviour under varied loading times and temperatures changes.Elastic behavior

At low temperature and short duration loads: Bitumen tends to act as an elastic solid,

returning to its original position after removal of the load; Excessively low temperature in conjunction

with rapid loading may cause brittle failure and cracking;

Prolonged low temperature can cause a build-up of internal stress resulting in cracking.


0

Viscoelastic properties Bitumen displays both elastic and

viscous behaviour, depending largely on temperature and load duration.

This viscoelastic character of bitumen results in its varied response behaviour under varied loading times and temperatures changes.Viscous behavior

At elevated temperature and long duration loads:

Bitumen acts as a viscous fluid - i.e. it undergoes plastic deformation that is not recovered

Flow takes place as adjacent molecules flow past each other

The force resisting this flow is related to the relative velocity of sliding


Many materials display time dependence in their elastic response

gum bread dough cheese

Viscoelastic materials possess both elastic and flow characteristics

Viscoelastic properties


Viscoelastic properties


Consider a material placed under a weight. A constant stress is applied, and we measure how the strain (∆h/h) changes with time

O r i g i n a lh

F

C o m p r e s s e d

∆ h

Elastic Material


Elastic Material

Originalh

F

Compressed

∆h ∆h

Time

Instantaneouselasticdeformation

Instantaneouselasticrecovery

force applied

force removed

Elastic Material


Originalh

F

Compressed

∆h

Instantaneouselasticdeformation

∆h

Timeforce applied

force removed

retardeddeformation(creep)

Instantaneouselasticrecovery

retardedrecovery

permanent deformation

Viscoelastic Material


Viscoelastic Material Unlike purely elastic substances, a viscoelastic

substance has an elastic component and a viscous component.

The viscosity of a viscoelastic substance gives the substance a strain rate dependent on time. Purely elastic materials do not dissipate energy (heat) when a load is applied, then removed.

However, a viscoelastic substance loses energy when a load is applied, then removed.

Hysteresis is observed in the stress-strain curve, with the area of the loop being equal to the energy lost during the loading cycle.

Since viscosity is the resistance to thermally activated plastic deformation, a viscous material will lose energy through a loading cycle.

Plastic deformation results in lost energy, which is uncharacteristic of a purely elastic material's reaction to a loading cycle.

Specifically, viscoelasticity is a molecular rearrangement.

When a stress is applied to a viscoelastic material such as a polymer, parts of the long polymer chain change position.

http://en.wikipedia.org/wiki/Viscosity

http://en.wikipedia.org/wiki/Hysteresis

http://en.wikipedia.org/wiki/Polymer


Rheology of Bitumen


What is Rheology of Bitumen?

Study of flow and deformation behavior of Bitumen

Rheology is the science of the flow and deformation of fluids and constitutes a fundamental engineering property of bitumen. The rheological properties of bitumen are influenced by both its temperature and chemical composition and the structure - or physical arrangement - of the molecules


Elastic Response


Viscous Response


Maxwell Model


Kelvin-Voigt Model


Combination of Maxwell and Kelvin-Voigt


Burger’s Model

Burger's model is often used to characterize the response of bitumen to imposed stresses.

A spring and dashpot in series (Maxwell model);o Spring and dashpot in parallel (Kelvin-Voigt model).


Burger’s Model


Burgers Model


Low temperature and short duration loading

At low temperatures and/or high frequency (short duration) loads, bitumen tends to act as an elastic solid, returning to its original position after removal of the load.

This almost purely elastic behavior can be represented by a simplified Burger's model as a spring in series with the Kelvin-Voigt model or even a spring only.

Excessively low temperatures in conjunction with rapid loading may cause brittle failure and cracking. Prolonged low temperatures can also cause a build-up of internal stresses in the bitumen, resulting in cracking as it interacts with the rest of the pavement structure.


High temperature and long duration loading At elevated temperatures and/or low frequency (prolonged duration) loads, bitumen acts as a viscous fluid.

It will undergo plastic deformation i.e. the deformation is not reversible.

Flow takes place as adjacent molecules slide past each other, the resulting friction or resistive force being related to the relative velocity of sliding.

The relationship of this resistive force and the relative velocity (of sliding) is termed "viscosity".

Under conditions of elevated temperature, pavements bound with bitumen will tend to rut under repeated applications of wheel loads, and the rutting will occur at a rate dependent on the temperature and rate of loading.

This plastic behavior of the bitumen at high temperatures can be offset by the interlocking action of the aggregate, which serves to resist permanent deformation.


Intermediate temperature behavior At intermediate temperatures bitumen displays

both elastic and viscous behaviour as represented in the Burger's model.

After an instantaneous elastic response, a gradual increase in strain with time takes place until the load is removed.

The change in strain with time is caused by the viscous behaviour of the material.

On removal of the load, the elastic strain is recovered instantaneously and some additional recovery occurs with time - known as delayed elasticity.

Ultimately a permanent residual strain remains, i.e. rutting, which is irrecoverable and is directly caused by viscous behaviour.


Response of asphalt in a simple creep test


Advantages of the viscoelastic behaviour of bitumen The most common state of bitumen is viscoelastic,

enabling it to exhibit the advantageous properties of both elastic and plastic materials;

As a binder it provides excellent adhesive properties with mineral aggregates;

Bitumen acts as a lubricant when heated, thereby facilitating spraying, coating of aggregates during hot mix manufacture, as well as compaction during laying;

Bitumen cools to become a glue, forming part of the solid matrix.

With a binder well-matched to the loading and temperature conditions, the most common response is elastic or viscoelastic, with only a limited plastic behavior.


Cutback Bitumen Cutback bitumen is a blend of penetration grade bitumen and

petroleum solvents. The choice of solvent determines the rate at which the bitumen will "set up" or cure when exposed to air. A rapid-curing (RC) solvent will evaporate more quickly than a

medium-curing (MC) solvent. The viscosity of the cutback bitumen is determined by the

proportion of solvent added - the higher the proportion of solvent, the lower is the viscosity of the cutback.

The solvent used in cutback bitumen is sometimes also referred to as the "cutter" or "flux".

When the solvent has evaporated, the binder reverts to the original penetration grade.

The advantage of cutback bitumen is that it can be applied at lower temperatures than penetration grades because of its lower Bitumen Solvents viscosity. A disadvantage is that cutback bitumen consumes non renewable energy resources which are ultimately lost through evaporation.


Creep: deformation that occurs over period of time when a material is subjected to a constant stress (at constant temperature)

Creep


1

2

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5

6

² L

Fixed end

Strain

Stress

Stress

Time

Time

Time

Time

Stress

Hookean solid

Newtonian Fluid

Viscoelastic

Solid

Liquide


Elastic Material: stress increases

immediately with strain and remains constant

Newtonian Fluid: stresses increases with application of strain, quickly declines to zero

Viscoelastic material: stress increases immediately, declines gradually over time. viscoelatic solid-decline is gradual and levels off

at e viscoelatic liquid, stress declines rapidly and

goes to zero


To illustrate how viscoelastic materials respond to applied loads it is common practice to represent material behaviour by a system of springs to simulate the elastic components, and dashpots to simulate the viscous behaviour as follows:

• Spring:1. o Elastic deformation;2. o Not time dependent;3. o No permanent

deformation.• Dashpot:

o Viscous deformation;o Time dependent;o Some permanent deformation.• Spring-dashpot in parallel Delayed elastic deformation;Time dependent;o No permanent deformation.


Elastic Response


Viscous Response


Maxwell Model


Bitumen plays a vital role in road construction typically as binder.

Application condition requires bitumen to behave as mobile liquid.There are three ways to reduce its viscosity:• Heat it• Dissolve it in solvents• Emulsify it.

In heating it involves some: • Energetic • Environmental and • Health problems As process is inefficient and involvesLoss of heat and even fumes causing air pollution

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In case using solvents: We make use of volatile dilatants like kerosene petroleum which adds to its cost although viscosity get reduced as it is uneconomical.


Types and grades of bituminous binders

Penetration grade bitumen

Penetration grade bitumen can be manufactured by straight-run distillation or by blending two base components (one hard such as 35/50 pen and the other soft such as 150/200 pen). Penetration grade bitumen is used either as a primary binder or base bitumen for the manufacture of:

1. Cutback bitumen;2. Modified binders;3. Bitumen emulsions.


Cutback Bitumen Cutback bitumen is a blend of penetration grade bitumen and

petroleum solvents. The choice of solvent determines the rate at which the bitumen will "set up" or cure when exposed to air. A rapid-curing (RC) solvent will evaporate more quickly than a

medium-curing (MC) solvent. The viscosity of the cutback bitumen is determined by the

proportion of solvent added - the higher the proportion of solvent, the lower is the viscosity of the cutback.

The solvent used in cutback bitumen is sometimes also referred to as the "cutter" or "flux".


Polymer modified bitumen The rheological properties of conventional binders

may be modified by the introduction of:• Elastomers;• Plastomers;• Crumb rubber;• Hydrocarbons.

Modification is costly and is normally justified when bituminous surfacings are subjected to severe conditions such as:

• Steep gradients;• Very high road surface temperature;• High traffic loading; or• Heavily trafficked intersections.

Modification may also be advantageous for surfacings on highly flexible and cracked pavements, where an improvement in the rheological properties of the bitumen is required.

Use in such applications should be guided by expert opinion.


Polymer modified bitumen

In addition to the primary aims above, the range of properties improved include

1. Durability;2. Aggregate retention;3. Resistance to permanent deformation;4. Resistance to fatigue cracking;5. Cohesion (internal strength);6. Elasticity;7. Viscosity less susceptible to temperature

changes.8. Modification agents



The primary aim of the modification of bitumen for use in structural layers is to increase the resistance of these layers to permanent deformation at high road temperatures without compromising the properties of these layers over the rest of the prevailing temperature range.

The use of polymer modified bitumen to obtain improved performance is rising as a result of increases in tyre pressures, axle loads and higher traffic volumes.

Improved performance can be achieved in two ways, both of which are aimed at reducing the permanent strain:1. An increase in the elastic component with an

associated reduction in the viscous component; and

2. Stiffening of the bitumen to reduce the total viscoelastic response of the layer.



Modification is achieved by the introduction of polymers (including crumb rubber), aliphatic synthetic wax or naturally occurring hydrocarbons.Polymers can be broadly categorized as "elastomers" (sometimes referred to as thermoplastic elastomers) for improving the strength and elastic properties of a binder, and "plastomers" (sometimes referred to asthermoplastic polymers) for increasing the viscosity of the bitumen.


Types and varieties of Modifiers


Bitumen Additives

A number of bitumen additives are employed, particularly in asphalt. These additives are not intended to modify or improve the rheological properties of bitumen; rather the intention is to improve certain performance characteristics to extend the service life of the asphalt.


What are emulsions?

An emulsion is a dispersion Of small droplets of one liquid in another liquid.

Emulsions can be formed by any two immiscible liquids, but in most emulsions one of the phases is

water. Oil-in-water (O/W) emulsions are those in which the continuous phase is water and the disperse

(Droplet) phase is an “oily” liquid. Water-in-oil (W/O) “inverted” emulsions are those

in which the continuous phase is an oil and the disperse phase is water.

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Types of emulsions:

(a) O/W emulsion, (b) W/O emulsion, (c) multiple W/O/W.

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BITUMEN EMULSION

Bitumen Emulsion is a 2-phase system consisting of • Bitumen• Water• Other Additives

• The bitumen is dispersed throughout the water phase in form of discrete globules, held in suspension by electrostatic charges stabilized by emulsifier

• The Emulsion contains 40-75% of bitumen,.1-2.5% emulsifier, 25-60% water and other ingredients Typically of 0.1 – 50 µm in diameter.

• It is mainly dark brown in color after breaking changes to black.

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WHY BITUMEN EMULSIONS ?

Primary objective is to use for road surfacing without much heating.

As main advantages this improves the handling of bitumen at room temperature.

Promotes surface interactions . Its mixture with the aggregate attains full strength. Economical and saves energy . Reduced atmosphere pollution. Water can also added before use to dilute as per

requirement. Rains can not effect it at the time of use and after use.


Types

Bitumen emulsions can be divided into four classes:

1) Cationic emulsions.2) Anionic emulsions.3) Non-ionic emulsions.4) Clay-stabilized emulsions.

The first two are most widely used

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Cationic emulsions If an electric potential is supplied

between two electrodes immersed in an emulsion containing positively charged particles of bitumen, they will migrate to the cathode.

This emulsion is said to be cationic.

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Anionic emulsions

If an electric potential is supplied between two electrodes immersed in an emulsion containing negatively charged particles of bitumen, they will migrate to the anode.

This emulsion is said to be anionic.

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Non-ionic emulsions

If the bitumen particles in the emulsion are neutral, then they will not migrate to any of the pole.

These type of emulsions are NON-IONIC.

Mainly used in road ways.

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Clay-stabilized emulsions

These are mainly used for industrial applications.

In these materials, emulsifiers are fine powders, often natural or processed clays and bentonites.

Particle size is very much less when compared with the bitumen particles in emulsions.

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Manufacture of Bitumen emulsions

Bitumen emulsions can be manufactured using batch process or continuous process.

Bitumen emulsions are made in continuous inline processes involving dispersing technologies like rotor stators, colloidal mills and static mixers.

High shearing forces are required for producing emulsions.

Colloidal mills contain high speed rotors. Hot bitumen and emulsifier are fed

simultaneously into colloidal mill.

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Manufacturing conditions The speed of rotors is in the range of

1000-6000 revs/min.

Bitumen is generally heated to temperature of 100-140 degree Celsius.

The viscosity of the bitumen is kept less than 2 poise.

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Figure 2. Schematic diagram of a bitumen emulsion plant


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As an alternative to colloid mill, a static mixer can be used.

This contains no moving parts.

The high shear necessary to produce an emulsion is generated by pumping the input materials at high speed.


Properties of bitumen emulsion

It is stable under transportation ,storage & application condition.

But it may break soon after application.It may have low viscosityIt may flow due to irregular spraying but not due to road

irregularities

Important properties of Bitumen emulsion:1. Stability2. Viscosity3. Breaking4. Adhesivity

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Emulsion stability

This property indicates the resistance ability to change properties over time.

As stability is very important in storage , transport & use.

Stable emulsion will change over time slowly. Reason for instability can be physical or chemical

process. As emulsion is a example of colloidal system in non

equilibrium state. Emulsion will go through several process like

flocculation, sedimentation, and coalescence leading to instability of emulsion

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Emulsion Viscosity

The viscosity of the bitumen emulsion is important for pumping and transportation.

In some applications, for example surface dressing, bitumen emulsion is sprayed on the road.

In this case the viscosity is critical. As it should be low enough to permit even

spraying but at the same time high enough to prevent run-off, once it is sprayed on the road.

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Emulsion breaking

Bituminous emulsions are designed to “break” deliberately in contact with moist aggregates, releasing a binder film on and between the mineral aggregates.

There can be two kind of breaking:1. Breaking of anionic bitumen emulsions2. Breaking of cationic bitumen emulsions

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Uses of Bitumen emulsion

Crack Filling: To stop entering water in structural layer of pavement Bitumen emulsions preferably containing rubber are used as they are inexpensive and effective.

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Grouting: It is the method of construction or stabilizing of road surfaces and footpath. Emulsion is applied to compacted dry aggregate and due its low viscosity it penetrates through void structure of the aggregate.


Soil Stabilization: For agricultural land where fresh top soil is susceptible to surface erosion ,bitumen emulsion can be used as binding agent also helps in retaining soil moisture & improving thermal insulation

Slip layer & concrete curing: Bitumen emulsions are used to create a membrane between layers of concrete to retain strength of upper layer by preventing water seepage into lower layers by avoiding rigid adhesion. Also it is sprayed on top surface to avoid evaporation of water.

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CE 2020: Construction Materials Dr. B. Munwar Basha IIT Hyderabad Bituminous Materials.

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Transcript of CE 2020: Construction Materials Dr. B. Munwar Basha IIT Hyderabad Bituminous Materials.