• Asphalt refining •Uses and properties

•Asphalt cement and physical tests •Asphalt cement grading system

•Rheological properties and pavement performance

The term bituminous materials is generally used to denote substances in which bitumen is present or from which it can be derived [Goetz and Wood, 1960].

Bituminous mixtures are generally used to denote the combinations of bituminous materials (as binders), aggregates and additives

Asphalt and bitumen : petroleum products Tar : dark colored product obtained from

destructive distillation of organic substance like coal, wood and bituminous shale’s.

Bitumen: A heavy fraction from oil distillation (also occurs as part of natural asphalt).

Tar: A viscous liquid obtained from distillation of coal or wood. Rarely used in construction currently in the UK.

Asphalt: A mixture of bitumen and mineral filler. Note that Hot Rolled Asphalt is a road surfacing material.

Defined as a mixture of bitumen with a substantial proportion of inert mineral matter.

Bitumen is used as a binding material in asphalt Asphalt is used primarily for road construction

and roofing materials due to its remarkable waterproofing and binding properties. The hard surfaces of roads, for example, depend on the ability of asphalt to cement together aggregates of stone and sand.

Natural Sources

Lake asphalts (Bermudez and Trinidad)

Gilsonite - occur in faults, large deposit in Utah, very hard substance, used in varnish/paper/powered form on roads

Rock asphalts - sandstone or limestone impregnated with asphalt (0 to 20% asphalt), usually too expensive for use in paving, found in KY, OK, AR, AL, TX, UT, CA

Petroleum Asphalts

Asphalt is obtained from crude oil by a process called FRACTIONAL DISTILLATION

Crude oil is a mixture of different hydrocarbons which are mutually soluble - fractional distillation is used to separate the fractions based on boiling point

Asphalt binder is simply the residue left over from petroleum refining

The composition of base crude oil from which asphalt is refined can vary widely and thus the asphalt yield from different crude oil sources can also vary widely

Crude oil is heated in a large furnace to about 340° C and partially vaporized.

It is then fed into a distillation tower where the lighter components vaporize and are drawn off for further processing.

The residue from this process (the asphalt) is usually fed into a vacuum distillation unit where heavier gas oils are drawn off.

Asphalt cement grade is controlled by the amount of heavy gas oil remaining.

Depending upon the exact process and the crude oil source, different asphalt cements of different properties can be produced.

Additional desirable properties can be obtained by blending crude oils before distillation or asphalt cements after distillation.

Bitumen or asphalt or their blend with flux oils having adhesive qualities for making mastic asphalt

Mastic asphalt : prepared by mixing the required mineral filler (eg. limestone, dust, sand or grit and coarse aggregate) with black bitumen heated to a liquid form. On cooling, it consolidates to a hard elastic block

Tough, durable, non-absorbent, damp proff, non-inflammable and noiseless

Types: Asphalt cement

Asphalt cutback

Asphalt emulsion Asphalt cement is an asphalt which has been

specially refined as to quality and consistency for direct use in the construction of asphalt pavements. An asphalt cement has to be heated to an appropriate high temperature in order to be fluid enough to be mixed and placed

Cutback asphalt is a liquid asphalt which is a blend of asphalt and petroleum solvents (such as gasoline and kerosine). A cutback asphalt can be mixed and placed with little or no application of heat. After a cutback asphalt is applied and exposed to the atmosphere, the solvent will gradually evaporate, leaving the asphalt cement to perform its function as a binder.

Emulsified asphalt (or asphalt emulsion) is an emulsion of asphalt cement and water that contains a small amount of emulsifying agent. In a normal emulsified asphalt, the asphalt cement is in the form of minute globules in suspension in water. An emulsified asphalt can be mixed and applied without any application of heat. After an asphalt emulsion is applied, sufficient time is required for the emulsion to break and the water to evaporate to leave the asphalt cement to perform its function as a binder. In an inverted emulsified asphalt, minute globules of water are in suspension in a liquid asphalt, which is usually a cutback asphalt. Inverted asphalt emulsions are seldom used in pavement applications.

Asphalt cement : hot-mix asphalt concrete for the surface layer of asphalt pavements

Asphalt concrete : patching and repairing asphalt and PC pavements

Liquid asphalts : pavement maintenance applications – fog seals, chip seals, slurry seals and microsurfacing

Asphalt pavement

Microsurfacing for preventive maintenance measure

Roof coverings, flashing, water-proofing of roofs

Damp proof courses Flooring material Tanking of basement floors (building water

barriers in basement)

Consistency of asphalt is greatly affected by temperature

Low temperature : Hard & brittle High temperature : Soft Grade of asphalt cement should be selected

according to climate Soft grade : cold climates Hard grade : hot climates

Robertson et al. (1991) describe asphalt behavior in terms of its failure mechanisms

Aging

Rutting

Fatigue cracking

Thermal cracking

Stripping

Bitumen is a black, oily, viscous material that is a naturally-occurring organic byproduct of decomposed organic materials

Becomes soft at moderate temperatures Extensively used for surfacing of road and

airport pavement

Straight run bitumen : bitumen distilled to a definite viscosity of penetration

which does not require further treatment like heating Blown bitumen : can be modified by heating until it becomes a liquid and

then passing air under pressure by which all the volatile compounds in it can be driven out.

Blow bitumen has a high softening point that if exposed directly to the sunrays for any length of time, it does not get soft.

Very hard in ordinary room temperature. Soluble in some solvents Commonly used for manufacturing joint fillers

Penetration grade

Basic form of bitumen and has to be heated before application

Cutback bitumen

Bitumen combined with other petroleum distillates

Bitumen emulsion

Product in liquid form formed in aqueos medium and stabilizing agents

Plastic bitumen Consists of bitumen thinner and suitable filler made

into a plastic form

Can be used for filling crack in masonry, stopping leakages etc.

Cutbacks Bituminous materials in solvents

Residual bitumen Solid substance at normal temperature and is

obtained as a residue during distillation of high-resin petroleum

Obtained when bitumen is combined with plastics

Also known as polymerized bitumen In this process, bitumen is not heated to high

temperature in its manufacture Lighter oils are also preserved in modified

bitumen, thus improving its flexibility and resistance to weathering

Modified-polymer bitumen are used for preparation of waterproofing works

Atactic Polypropylene (APP)

Plastomer

Generally stronger and stiffer

Sequenced Butadiene Styrene (SBS)

Elastomer

Greater flow for expansion and waterproofing qualities

Bitumen is specified by the term ‘penetration’ Penetration grade bitumen is semi-solid ay

ambient temperature and required to be heated to make it fluid enough for applications such as waterproofing

Specification 80/100 – penetration of standard needle at temperature of 25oC of depth between 80-100mm.

Tar is different from bitumen and there is different types of tar

Coal tar

Wood tar

Mineral tar

Obtained by heating coal in closed iron vessels to form coke

As the residue of the distillation of coal to produce coke, coal tar is a thick black liquid the consistency of a thick pudding

Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous.

Mostly used for roads

Raw coke

Obtained by distillation of pine wood and other resinous wood

Contains creosote oil – strong preservative property for wood and also repels termites if applied on wooden posts buried in the ground

Creosote is the portion of chemical products obtained by the distillation of a tar that remains heavier than water, notably useful for its anti-septic and preservative properties

Obtained by distilling bituminous shale’s In addition to use as a preservative of wood,

also used as a water proofing paint in many situations due to very good adhesive power

A graded stone mixture coated with tar is used for tar macadam and when the mixture is coated with bitumen, it is called bitumen macadam

Used for pavements and walkways Mastic asphalt : used in city roads for smooth

riding surface

Property Asphalt Bitumen Tar

Existing state Solid or semi-solid Usually solid at normal temperatures

Solid as a viscous liquid

Colour Blackish brown Dark black Deep black

Effect on heating Burns with smoke and become plastic at 250oC

Becomes liquid on heating

Becomes less viscous on heating

Adhesive power Not much Good Very good

Carbon content Less More Most

Setting time Not much Not much More

Resistance to acid and water

Good Good Less

Paint

Used for manufacture of bituminous paints and other surface treatment

Industrial blown or R grade is mainly used for this purpose

Roofing

Roofing felts and shingles (covering of roof) are made of fibres or plastics impregnated with penetration-grade bitumen and coated with blown-grade bitumen

Damp proofing

Prefabricated mats which are sprayed with blown bitumen are used for damp proofing

Also used as small ‘water retaining, bituminous walls’ at refuse disposal sites to prevent pollution from spreading

Tanking of basements

Asphalt and bitumen are the usual choices for water proofing of basements known as tanking of basement

Tanking is a term that is used when asphalt is formed to completely seal a void or area to keep moisture/water out or as a tank to keep liquid in.

Protection of structures

Used as a protecting coating (by impregnation) for concrete elements such as piles, slab etc.

Over this coating, organic binders of 10-15mm thickness are also applied to prevent bitumen from eroding of

Pavements

Extensively used for the construction of roads, runways, taxiways, etc.

Preservation of stones

Some of the materials used for stonework preservation from attach by salts and other substance present in the ground or in the atmosphere

One of the specifications for waterproofing in building work

‘The surface shall be painted uniformly with bitumen of approve quality such as “residual type”, “petroleum bitumen, penetration 80/100, hot cutback bitumen or equivalent after heating to the required temperature as per specification of the manufacturers shall be used.’

Measure of the hardness of the bituminous materials

The depth in milimeters to which the standard tapered needle penetrates vertically under a load of 100g in 5 seconds at a temperature of 25oc

This test measures only the consistency of the bitumen binders and has no relation to its binder capacity

Specification 80/100 => penetration between 80 to 100mm

Temperature at which the bitumen softens

Assemble the apparatus with the rings, thermometer and ball guides in position.

Fill the beaker with boiled distilled water at a temperature 5.0 ± 0.5oC per minute.

With the help of a stirrer, stir the liquid and apply heat to the beaker at a temperature of 5.0 ± 0.5oC per minute.

Apply heat until the material softens and allow the ball to pass through the ring.

Record the temperature at which the ball touches the bottom, which is nothing but the softening point of that material.