Bitumen , how bitumen is used in infrastructure development

What is bitumen?

Bitumen is the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. However, in the construction industry, you may often hear bitumen either attached to the word asphalt (asphalt bitumen) or where the two terms are used interchangeably.
In general terms, Bitumen -a viscous and sticky liquid- is used to bind the stone, sand and gravel that make up the pavement for our roads and highways.

These is the difference between asphalt and bitumen.
Most roads all around the world are paved with this material, so it’s no wonder that 100 million tons or 700 barrels of bitumen are used each year. China leads the world in production at over 21 million metric tons, followed closely by the United States, which produces just under 20 million metric tons.*

In 2017, about 2.8 million barrels of bitumen were produced per day in the oil sands of Alberta, Canada, which holds the third-largest oil reserves in the world, after Venezuela and Saudi Arabia.
Bitumen is a common binder used in road construction. It is principally obtained as a residual product in petroleum refineries after higher fractions like gas, petrol, kerosene and diesel, etc., are removed. Indian Standard Institution defines Asphalt as a black or dark brown non-crystalline soil or viscous material having adhesive properties derived from petroleum crude either by natural or by refinery processes.

asphalt is a solid or semi-solid material from dark brown to black in colour. It is one of the thermoplastics found in nature, but today it is mainly produced in oil refineries. From a chemical-physical point of view, bitumen is a complex mixture of various hydrocarbons.Bitumen offers a high adhesive strength and watertightness.

It is resistant to most acids, bases and salts and was the first oil product that man has ever used in practice – preferably as an insulating compound or binder. Solid at room temperature, Asphalt can be emulsified with water after heating and recycled as well. Thanks to all these properties, bitumen is now an indispensable material in road construction and is also used in a wide range of industrial applications.

Understanding Asphalt

Asphalt is generally for industry use. Asphalt was first used for its natural adhesive and waterproofing characteristics, but it was also used as a medicine. It was used to bind building materials together, as well as to line the bottoms of ships. ancient civilizations traded the material. Herodotus, a fifth-century BC Greek historian, claimed that the walls of ancient Babylon contained bitumen.

Asphalt is composed of complex hydrocarbons and contains elements such as calcium, iron, sulfur, and oxygen. The quality of material and ease of production depends on the source and type of crude oil it is derived from. The material is used most often in road paving. Most roads in the United States are made of either bitumen or a combination of Asphalt and aggregates, such as concrete. Engineers replacing asphalt roads can reuse the material on other road projects. Manufacturers use it in the creation of roofing products due to its waterproofing qualities.

Under heavy loads, Asphalt can deform permanently, depending on the composition of the asphalt mixture, the ambient temperature, and the amount of stress places on the material. Asphalt oxidizes, which can leave the asphalt brittle and result in it cracking.

USES OF ASPHALT

Most refined bitumen is used in the construction industry. Mainly, it serves its use in paving and roofing applications. 85% of all Asphalt is used as a binder in asphalt for roads, runways, parking lots, and foot paths. Gravel and crushed rock are mixed with thick Asphalt, holding it together and it is then applied to roadways. 10% of the bitumen used worldwide is used in the roofing industry as its waterproofing qualities help make roofs function well. 5% of bitumen is used for sealing and insulating purposes in various building materials such as carpet tile backing and paint.
In addition to these main uses, Asphalt also has many minor uses. Other examples are soundproofing, explosives, mildew protection, a binder in briquettes, a backing to mirrors, shoe soles, fence post coating and soil stabilization.

asphalt (or asphalt) is primarily used, when mixed with mineral aggregates, to produce paving materials. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.
Most natural bitumen contain sulfur and several heavy metals such as nickel, vanadium, lead, chromium, mercury and also arsenic, selenium, and other toxic elements. Bitumen can provide good preservation of plants and animal fossils.
Naturally occurring crude Asphalt impregnated in sedimentary rock is the prime feed stock for petroleum production from “oil sands”, currently under development in Alberta, Canada. Canada has most of the world´s supply of natural Asphalt, covering 140,000 square kilometers (an area larger than England), giving it the second largest proven oil reserves in the world. The Athabasca oil sands is the largest bitumen deposit in Canada and the only one accessible to surface mining, although recent technological breakthroughs have resulted in deeper deposits becoming producible by in-situ methods. Because of oil price increases since 2003, upgrading bitumen to synthetic crude oil has become highly profitable.

As of 2006 Canadian crude bitumen production averaged about 1.1 million barrels (170,000 m3) per day and was projected to rise to 4.4 million barrels (700,000 m3) per day by 2020. The total amount of crude bitumen in Alberta which could be extracted is estimated to be about 310 billion barrels (50×10^9 m3), which at a rate of 4,400,000 barrels per day (700,000 m3/d) would last about 200 years.
In the past, bitumen was used to waterproof boats, and even as a coating for buildings with some additives.

The Greek historian Herodotus said hot Asphaltwas used as mortar in the walls of Babylon. It is also possible that the city of Carthage was easily burnt due to extensive use of Asphalt in construction.
Asphalt was also used in early photographic technology. It was most notably used by French scientist Joseph Nicéphore Niépce in the first picture ever taken. The bitumen used in his experiments were smeared on pewter plates and then exposed to light, thus making a black and white image. It was similarly used to print millions of photochrom postcards.

Thin Asphalt plates are sometimes used by computer enthusiasts for silencing computer cases or noisy computer parts such as the hard drive. Bitumen layers are baked onto the outside of high end dishwashers to provide sound insulation.

Asphalt also is used in paint and marker inks by some graffiti supply companies (primarily Molotov) to increase the weather resistance and permanence of the paint and/or ink, and to make the color much darker.
Asphalt was the nemesis of many artists during the 19th century. Although widely used for a time, it ultimately proved unstable for use in oil painting, especially when mixed with the most common diluents, such as linseed oil, varnish and turpentine. Unless thoroughly diluted, Asphalt never fully solidifies and will in time corrupt the other pigments with which it comes into contact.

The use of Asphalt as a glaze to set in shadow or mixed with other colors to render a darker tone resulted in the eventual deterioration of a good many paintings, those of Delacroix being just one notable example.

Properties of Asphalt

• Adhesion: Bitumen has the ability to adhere to a solid surface in a fluid state depending on the nature of the surface. The presence of water on the surface will prevent adhesion.
• Resistance to Water: Bitumen is water-resistant. Under some conditions, water may be absorbed by minute quantities of inorganic salts in the bitumen or filler in it.
• Hardness: To measure the hardness of Asphalt, the penetration test is conducted, which measures the depth of penetration in tenths of mm. of a weighted needle in Asphalt after a given time, at a known temperature. Commonly a weight of 100 gm is applied for 5 sec at a temperature of 77 °F. The penetration is a measure of hardness. Typical results are 10 for hard coating asphalt, 15 to 40 for roofing asphalt and up to 100 or more for waterproofing bitumen.
• Viscosity and Flow: The viscous or flow properties of Asphalt are of importance both at high temperature during processing and application and at low temperature to which Asphalt is subjected during service. The flow properties of bitumen vary considerably with temperature and stress conditions. Deterioration, or loss of the desirable properties of bitumen, takes the form of hardening. Resultantly, a decrease in adhesive and flow properties and an increase in the softening point temperature and coefficient of thermal expansion.
• Softening point: Softening point is the temperature at which a steel ball falls a known distance through the Asphalt when the test assembly is heated at a known rate. Usually, the test consist of a (3/8)in dia steel ball, weigh 3.5 gm, which is allowed to sink through a (5/8) in dia, (1/4) in the thick disk of bitumen in a brass ring. The whole assembly is heated at a rate of 9 °F per min. Typical values would be 240 °F for coating grade asphalts, 140 °F to 220 °F for roofing asphalt and down to 115 °F for bituminous waterproofing material.
• Ductility: The ductility test is conducted to determine the amount bitumen will stretch at a temperature below its softening point. A briquette having a cross-sectional area of 1 in2 is placed in a tester at 77 °F. Ductility values range from 0 to over 150 depending on the type of Asphalt

Bitumen has the following five characteristic properties

• Adheres
• Elastic
• Plastic
• Viscoelastic
• Ages
• Hardens

1.  ADHERES
Bitumen has excellent adhesive qualities provided the conditions are favorable. However in presence of water the adhesion does create some problems. Most of the aggregates used in road construction possess a weak negative charge on the surface. The Asphalt aggregate bond is because of a weak dispersion force. Water is highly polar and hence it gets strongly attached to the aggregate displacing the bituminous coating.
2.  ELASTIC
When one takes a thread of bitumen from a sample and stretches or elongates it, it has the ability to return to a length close to its original length eventually. For some bitumens this process may take longer than others. This property is referred to as the elastic character of bitumen.
3. PLASTIC
When temperatures are raised, as well as when a load is applied to Asphalt, the bitumen will flow, but will not return to its original position when load is removed. This condition is referred to as plastic behavior. Applying a load means that you put a weight on the bitumen in order to subject it to stress. This could be in a lab or in the bitumens final position in the road and it is done to assess the bitumens reaction to the load.
4.VISCOELASTIC
Asphalt has a Viscoelastic character. Its behavior may be either viscous or elastic depending on the temperature or the load it is carrying. At higher temperatures there is more flow or plastic behavior, while at lower temperatures and short duration loading, the bitumen tends to be stiff and elastic. At intermediate temperatures it tends to be a combination of the two.
5. AGES
Aging refers to changes in the properties of bitumen over time, which is caused by external condition. These changes are visible as cracks or crumbling areas. When bitumen is exposed to atmospheric conditions, the bitumen molecules react with oxygen, which results in a change of the structure and composition of the Asphalt.

This process of combining with oxygen, called oxidation, causes the bitumen to become brittle and hard and to change colour from dark brown or black to grey. This change is usually referred to as oxidative hardening or age hardening. This form of ageing occurs more frequently in warmer climatic or during warm seasons, causing older pavements to crack more easily. The condition can also occur where the surface films of bitumen are thin, or if there has been inadequate compaction during construction.

grades can be classified as follows:

• Penetration Bitumen (30-40, 40-50, 60-70, 85-100, 80-100)
• Viscosity Grade (VG-10, VG-20, VG-30, VG-40)
• Cutback  (Rapid-Curing, Medium-Curing, Slow-Curing)
• Emulsion  (CRS, CMS, CSS)
• Oxidized Bitumen (75/30, 85/25, 85/40, 95/25, 105/35, 115/15)
• Modified asphalt

Geologic Origin

Naturally occurring deposits of Asphalt are formed from the remains of ancient, microscopic algae and other once-living things. These organisms died and their remains were deposited in the mud on the bottom of the ocean or lake where they lived. Under the heat and pressure of burial deep in the earth, the remains were transformed into materials such as Asphalt, kerogen, or petroleum.

As asphalts are also found in meteorites and Archean rocks it is possible that some asphalts are primordial material formed during accretion of the Earth and reworked by bacteria that consume hydrocarbons. Bitumens are associated with lead-zinc mineralizations in Mississippi Valley-type deposits.

Tar and Natural Asphalt

Petroleum Asphalt is often confused with tar. Although Asphalt and coal tar are similarly black and sticky, they are distinctly different substances in origin, chemical composition and in their properties. Coal tar is produced by heating coal to extremely high temperatures and is a by-product of gas and coke production.

It was widely used as the binding agent in road asphalt in the early part of the last century but has since been replaced by refined Asphalt. Tar sands, also called oil sands, are deposits of a mixture of fine clay, sand, water, and variable amounts of Asphalt which is a black, high-sulfur, tar-like, heavy oil. Tar sands are sedimentary rocks and the Asphalt is an asphaltic substance. Typical tar sand is composed of approximately 83% sand, 13% Asphalt, and 4% water (by weight percent). Tar sands containing more than 6% by weight of Asphalt are considered to have commercial potential.

The difference between oil shale and tar sand is that the bituminous matter in shale is solid, whereas, the bituminous matter in tar sand is a highly viscous liquid. Oil which is particularly thick and viscous is called heavy oil, or more colloquially, tar or asphalt.

Naturally-occurring asphalt, sometimes also called natural asphalt, rock asphalt, lake asphalt or oil sand, has been used as an adhesive, sealant and waterproofing agent for over 8,000 years. But it occurs only in small quantities and its properties are quite different from refined bitumen.