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Difference between Bitumen and Tar

Bitumen is a byproduct of refining petroleum crude through distillation. In its refined form, petroleum can be anything from the simplest hydrocarbon gas—methane—to the hardest bitumen, whose components have molecular weights in the millions. Thermoplastic amorphous aromatic rubber (TAR) is a byproduct of destructive distillation. Paving grades refer to bitumen that is used for waterproofing structures and industrial floors, whereas industrial grades are used for paving roadways and airfields.

Fig1: Bitumen

What is Bitumen?
Bitumen, also known as asphalt, is a black, sticky, highly viscous liquid or semi-solid form of petroleum. It is a naturally occurring substance and is one of the primary components of crude oil. Bitumen is a complex mixture of hydrocarbons, mainly aromatic compounds, and polycyclic hydrocarbons. Bitumen is widely used for paving and repairing roads. A binder or adhesive holds together aggregates, such as sand, gravel, and crushed stone, to create asphalt concrete. This mixture is then used to pave roads, highways, airport runways, and other surfaces. Bitumen provides strength, durability, and resistance to weather and traffic loads, making it ideal for road construction.

Apart from its use in road paving, bitumen has various other applications. It is used in waterproofing products, such as roofing felt, membranes, and shingles. Bitumen also manufactures coatings, sealants, adhesives, and insulation materials. In some regions, bitumen is utilized as a fuel source for heating and industrial processes.

How is Bitumen Made?
The procedure for the manufacturing of bitumen can be described as follows:

Properties Of Bitumen:
(i) Viscosity: Bitumen has a high viscosity, which means it is thick and flows slowly. This property allows it to adhere to aggregates and form a strong bond, making it an excellent binder for road construction.

(ii) Adhesion: Bitumen exhibits strong adhesive properties, allowing it to stick to various surfaces such as aggregates, concrete, and metals. This property is essential for creating durable asphalt pavements and waterproofing structures.

(iii) Waterproofing: Bitumen is highly impervious to water, making it ideal for waterproofing applications. It is a barrier, preventing water penetration and protecting structures from moisture damage.

(iv) Elasticity: Bitumen displays elasticity, meaning it can deform under stress and return to its original shape once removed. This property allows bitumen pavements to withstand traffic loads and temperature changes without significant cracking.

(v) Thermal Properties: Bitumen has good thermal stability and can withstand various temperatures. It remains solid at lower temperatures and does not melt or flow excessively at high temperatures, which is crucial for maintaining the structural integrity of roads in different climates.

(vi) Durability: Bitumen is known for its durability and resistance to aging. It can withstand the effects of weathering, oxidation, and chemical attacks, ensuring the longevity of asphalt pavements.

(vii) Flexibility: Bitumen pavements have inherent flexibility, enabling them to accommodate slight movements in the underlying soil or traffic loads without cracking. This flexibility contributes to the overall strength and durability of asphalt roads.

(viii) UV Resistance: Bitumen resists sun ultraviolet (UV) radiation. It can withstand prolonged exposure to sunlight without significant degradation or color fading, making it suitable for outdoor applications.

(ix) Insulating Properties: Bitumen has relatively good thermally and electrically insulating properties. It can act as a thermal barrier, reduce heat transfer, and provide electrical insulation in certain applications.

(x) Recycling: Bitumen is a recyclable material that can be reclaimed and reused in various ways. Reclaimed bitumen can be incorporated into new asphalt mixtures, reducing the demand for new bitumen and promoting sustainability in road construction.

Uses of Bitumen:
(i) Road Construction: Bitumen is primarily used in road construction and paving. It is a binder in asphalt concrete, creating durable and flexible road surfaces. Bitumen binds the aggregates, providing strength and resistance to heavy traffic loads.

(ii) Roofing and Waterproofing: Bitumen is widely used in the construction industry for roofing and waterproofing purposes. It is a waterproofing material in flat roofs, forming a protective layer against water penetration and providing excellent weather resistance.

(iii) Pavement Preservation: Bitumen-based products are used for pavement preservation to extend the life of existing asphalt roads. Techniques like chip sealing and slurry sealing involve applying bitumen emulsions or thin layers of bitumen on the road surface to seal cracks, prevent moisture intrusion, and improve skid resistance.

(iv) Airport Runways: Bitumen is used in constructing airports and taxiways due to its ability to withstand heavy aircraft loads. Asphalt concrete with bitumen provides a smooth, durable surface for safe landing and takeoff.

(v) Bridge Deck Waterproofing: Bitumen membranes are employed to waterproof bridge decks, protecting the underlying structure from water damage and corrosion. These membranes provide a flexible barrier that prevents moisture ingress, extending bridges’ lifespan.

(vi) Pipe Coating: Bitumen coatings protect pipes against corrosion and abrasion. The coatings provide a protective layer that ensures the longevity and integrity of the pipes, particularly in oil and gas transportation.

(vii)Paints and Coatings: Bitumen is used to manufacture paints and coatings. Bituminous paints provide excellent corrosion resistance and are applied to metal surfaces, such as pipes, tanks, and structural elements, to protect them from the elements.

Fig2: Tar

What is Tar?
Tar is a black, sticky liquid with a high carbon concentration. Tar is a highly viscous liquid. Similar to bitumen, tar is a mixture of several chemical compounds. Tar is a pitch-black substance. Temperature extremes have a profound effect on tar. Tar is hard and brittle at low temperatures and malleable and liquefied at high ones. Because of this, tar is not a good choice for places with extreme temperature swings. Tar has a low viscosity compared to bitumen. Tar’s low cost and abundance make it a versatile substance with many applications.

How is Tar Made?
Here are the primary steps involved in making tar:

Uses of Tar:
(i) Roofing: Tar is widely used in roofing materials, particularly in built-up systems. It is combined with roofing felt or fiberglass layers to create a durable and waterproof barrier.
(ii) Waterproofing: Tar is an effective waterproofing agent to seal and protect various construction elements. It can be applied to foundations, basements, tunnels, and underground structures to prevent water infiltration and damage.
(iii) Road construction: Tar forms asphalt when mixed with aggregate materials. Asphalt is extensively used in road construction for surfacing roads and highways. It provides a smooth, durable, weather-resistant surface that can withstand heavy traffic loads.
(iv) Paving and surfacing: Tar-based materials like asphalt are used for parking lots, driveways, walkways, and other surfaces. These materials offer excellent strength, flexibility, and resistance to weathering, making them suitable for a wide range of applications.
(v) Preservation of wood: Tar, specifically creosote derived from coal tar, is utilized for preserving wood in construction. It is commonly applied to utility poles, railway ties, and other wooden structures to enhance their resistance to decay, insects, and fungi.

Difference between Bitumen and Tar:

In summary, bitumen and tar is black, sticky substances used in construction applications, but they differ in composition, manufacturing processes, physical properties, and environmental considerations. Bitumen is derived from petroleum, while tar can be obtained from various organic materials. Bitumen is widely used in road construction and has lower environmental concerns, whereas tar’s usage has decreased due to its toxicity and environmental impact.

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2. Applications & Uses of Bitumen in Construction. (2020, February 12). Applications & Uses of Bitumen in Construction -BuildersMART.
3. What is Tar | Uses of Tar | Difference Between Asphalt and Bitumen & Tar | What is Road Tar (2023). (2020, December 3). HPD TEAM.
4. Darbandizadeh, M. (2020, September 14). What are the Differences between Bitumen, Tar and Asphalt? Infinity Galaxy.
5. Definition and difference between bitumen and Tar – Advantages and disadvantages of Bitumen. (2020, May 16). Definition and Difference Between Bitumen and Tar – Advantages and Disadvantages of Bitumen.
6. M. (2022, November 5). Difference between Bitumen And Tar – MDM Tool Supply. MDM Tool Supply.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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