Coal Tar vs Asphalt: Difference and Comparison

Key Takeaways

  1. Coal Tar: Coal tar is a thick, black liquid derived from coal while producing coke or coal gas. It is commonly used in various applications, including road pavement, roofing materials, and sealants. Coal tar provides excellent waterproofing and durability properties.
  2. Asphalt: Asphalt, or bitumen, is a black, sticky, semi-solid form of petroleum. It is extensively used in road construction and maintenance. Asphalt is mixed with aggregates to create asphalt concrete, forming the top road layer. It offers flexibility, weather resistance, and a smooth riding surface.
  3. Difference: While coal tar provides waterproofing properties, asphalt offers flexibility and weather resistance for durable road surfaces.

What is Coal Tar?

A derivative of coke and gas emitted by coal is known as coal tar. It is a by-product obtained when a hydrocarbon is carbonized; for instance, coal carbonization uses coal tar as a by-product. It is black or brown and is mainly found in liquid form.

Coal tar is either found in liquid r semi-solid forms. It consists of phenols and heterocyclic components along with PAHs. When coal tar is distilled, it emits major properties of the pitch. Certain organic substances like wood and coal are destroyed to produce coal tar.

Coal tar has bitumen quantity present in it. Depending on the manufacturer, it may vary. Coal tar is highly carcinogenic; it can cause cancer as it contains PAHs in higher quantities. Other than that, coal tar is used to treat psoriasis and is applied to the skin; it is combined with ultraviolet light for therapy.

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Coal tar is used for surfacing roads in the paving industry, and railroad works. Coal tar is used in generic medication, and it is also used in synthesizing dyes. They are used as raw materials in hair dyes as well.

Coal tar is also used for roofing and manufacturing green blocks, paints, and photographic materials.

What is Asphalt?

A sticky and dark by-product found during the refining of petroleum consisting of hydrocarbons is known as asphalt or bitumen. Asphalt consists of minerals and bitumen and is either solid (glassy) or liquid.

Asphalt is used in building roadways. Asphalt used for surfacing roadways is made by mixing sand, crushed stones, and other reclaimed materials. Asphalt glue is another component obtained from heavy crude oil compounds.

When heated, asphalt is softened and elastic. Asphalt can protect various surfaces from weathering and damage if sprayed in the right quantities. It is used for soundproofing and waterproofing in households. Mainly, asphalt is used as a binding agent or as an adhesive.

At early ages in Mohenjo-Daro, asphalt was used to stop water between the reservoir walls. In many middle eastern countries, asphalt is used to seal waterworks and pave streets even today. The major commercial source of asphalt was an island from Trinidad, but it declined as petroleum became the major source.

Various vein asphalts like gilsonite are used as heat-resistant enamels and can be found by mining. Petroleum asphalt has an extremely flexible form and can be used as a light oil for road or heavy industrial works.

Difference Between Coal Tar and Asphalt

  1. Coal tar is a derived material; conversely, asphalt is a composite material.
  2. Coal tar is found artificially as it is a by-product. Conversely, asphalt is found naturally.
  3. Coal tar is comparatively riskier for human health than asphalt.
  4. The amount of polycyclic aromatic hydrocarbons (PAH) is extremely high in coal tar; conversely, the amount of polycyclic aromatic hydrocarbons (PAH) is relatively lesser in asphalt.
  5. Coal tar is a by-product of coke; on the other hand, asphalt is a mixture of stones and sand.
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Comparison Between Coal Tar and Asphalt

Parameters Of ComparisonCoal TarAsphalt
TypeDerived materialComposite material
OccurrenceArtificialNatural
PAH levelMoreLess
Health riskMoreLess
ColourBlackBrown or black
Bitumen levelLowHigh
ConsistencyLiquid or semi-solidLiquid or glassy-solid
References
  1. https://www.sciencedirect.com/science/article/pii/S0045653510007320
  2. https://onlinelibrary.wiley.com/doi/abs/10.1162/jiec.2007.1106

Last Updated : 30 July, 2023

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