Asphalt Essay: Types, Ingredients, Production, and Compaction Methods

This essay delves into the multifaceted world of asphalt, a crucial material in civil engineering. It begins by defining asphalt and differentiating various types, including coal tar pitch, petroleum asphalt, natural asphalt, porous asphalt, hot mix asphalt, and mastic asphalt, outlining their unique characteristics and applications. The essay then explores the key ingredients of asphalt, emphasizing the critical role of aggregates in providing strength and stability to construction projects, and discusses the properties and classification of different rock types used as aggregates. The asphalt production process is explained, detailing the extraction of asphalt from crude oil through distillation and the use of artificial aggregates. Furthermore, the essay examines the grading, shape, and texture of aggregates, and their classification based on origin, texture, and density. The concept of porosity in aggregates is also discussed. The essay concludes with an in-depth analysis of asphalt compaction methods, including initial, static, and vibratory compaction, as well as the equipment used. It highlights the importance of test reporting and safe handling procedures when working with asphalt, making this a comprehensive resource for students and professionals alike.

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Asphalt
The definition of asphalt is a black or brown, tar-like substance that is used to cover roadways
and is usually mixed with gravel.
Types of asphalt
1. Coal tar pitch
This is a type of asphalt that results from coke production. It is the byproduct of black residue
that remains in the distillation still after the process of distillation has been completed. Moreover,
this type of asphalt is usually similar to the refined tar with an exception to its physical properties
(Oikonomou, 2005). The most common method to distinguish this asphalt with the refined tar is
the substance softening point. The tar pitch does emit a special smell when heated to high
temperatures.
2. Petroleum asphalt
This is the residue of crude oil after distillation. The asphalt is usually dark in color with a shiny
outlook. It is also resistance to very high temperatures and contains little volatile organic
compounds due to the high temperature that it is usually subjected to the distillation process.
Even though, there are usually some hydrocarbons that exist which can cause danger to humans.
3. Natural asphalt
This kind of asphalt is usually found deposited in the underground as a result of their
accumulation over time. Fortunately, such asphalts are usually harmless to humans due to their
natural evaporation and oxidation.

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4. Porous asphalt
This asphalt allows water and other liquids to pass through the ground surface into the
underground beds. This type of asphalt is found below the car parking lots where they assist in
the enhancement of stormwater so as to improve its quality as it seeps underground.
5. Hot Mix Asphalt
This asphalt is the most recommended for the construction of the driveways. This is because it
gives the best design features and finished appearances. In addition, it is usually strong and can
withstand thawing and freezing. The hot mix asphalt is also resistant to salt water and requires
low maintenance (Zimmermann, 2002). Generally, the asphalt is the cheapest among the types of
asphalt discussed above.
6. Mastic asphalt
It is also known as sheet asphalt. It contains fewer amounts of bitumen content. As such , it is the
most suitable for the construction of floors, roofs, footing paths.
Key ingredients of asphalt

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Importance
Aggregate do play an important part in providing strength to concrete during the construction
process. In addition, the transition zones of concrete is the region between an aggregate and
cement paste and is responsible for providing compressive strength to cement (Hollon, 2001).
Properties of rock types
Although aggregate is considered inert filler, it is a necessary component that defines the
concrete’s thermal and elastic properties and dimensional stability. Aggregate is classified as two
different types, coarse and fine. Coarse aggregate is usually greater than 4.75 mm (retained on a
No. 4 sieve), while fine aggregate is less than 4.75 mm (passing the No. 4 sieve). The

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compressive aggregate strength is an important factor in the selection of aggregate (Linden,
1997).
Asphalt production
Asphalt can be manufactured from either oil refinery of naturally through deposition. For
example, a manufacturer from crude petroleum oil is obtained through separation of various
fractions through the distillation process. After the separation of the fractions from the
distillation, the end products are usually paraffin, gasoline, asphalt, lubricating oil among others.
Due to the high density of asphalt, it is usually deposited at the base of the distillation chamber.
The refining process begins at the piping of the crude from the storage tank to the tubers where
the temperature is highly raised (Geller, 2004). This always happens to achieve primary
distillation. After this, it is made to enter atmospheric distillation tower. Here, the crude oil is
subjected to pressure which makes the lighter and most volatile components to vaporize. It is
then separated on further heating and pressurization to obtain gasoline, kerosene and diesel oil
among other petroleum products. The heavy residue that is left is referred to as topped crude
(Evangelista and Brito, 2007). The topped crude is usually moved to vacuum distillation which
removes high boiling fractions so as to reach the asphalt.
Artificial aggregate is a light mixture of fly ash binders and water. They are usually round
shaped. However, it can be made into any other irregular form.

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Artificial aggregates are usually advantageous in that it is very firm, have a very fast
absorbability and a low volumetric weight. This property usually makes it to be used in concrete
mortar without changing their consistency.
Grading of aggregates
Fine aggregates- according to the international standards specification for the architects, such
aggregates pass 4.75 mm in diameter size. The aggregates may be described as natural sand,
crushed stone sand or crushed gravel sand (Zakaria et al., 2006).
Uses of aggregates
Aggregates are usually important in that they provide strength during the construction process.
The fine aggregates, for instance, the fine aggregates ensures that there is no weakness in the

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construction structure. In addition, the fine aggregates are responsible for the maximum surface
area coverage with the concrete to achieve a smooth layer (Paranavithana and Mohajerani,
2006).
Aggregate shape and texture
The shape and texture of aggregate are usually important for effective compaction, workability
and construction purposes. Different shapes of an aggregate are preferred by different purposes
in which it serves. For instance, the shape of an aggregate defines its ability to interlock with
each other therefore providing stiffness and strength in the construction process. There are also
rounded particles that are known to create less particle to particle interlocking as compared to the
angular counterparts.
Classification of aggregates based on origin
i. Natural aggregates
Natural aggregates are those that are naturally occurring and are buried within the river, lakes or
ocean beds. They are characterized with round shaped, smooth surfaces with waterborne
fragments of rocks. They are usually graded in different sizes. There are those with larger gravel
pieces while others have smaller gravel sizes (Van et al., 2000). They are constituted with
minerals such as the granite, limestone, sandstone among others.
ii. Bye product
This includes the materials that arise from industrial wastes and other engineering operations
which possess best qualities of aggregates. Examples include cinder found from burning of coal
locomotives.

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Classification based on texture
i. Fine aggregates
Fine aggregates in most cases do consist of the natural sand or even the crushed stone with the
majority of the particles passing through a sieve of 9.5mm.
ii. Coarse aggregates
In this case, the coarse aggregates are usually obtained from the crushing or breaking down of
rocks with the help of explosives and machines leaving large particles of aggregates of sizes
ranging from 6mm or above. They are necessary for construction purposes as well.
Classification of aggregates based on density
The aggregates may be classified with reference to their nature of weighing. For instance, there
are normal weight aggregates, heavyweight aggregates, and lightweight aggregates. The normal
weight aggregates are the natural mineral aggregates and do have a bulk specific gravity of about
2.5. This is the most commonly used class of material in the developed and developing countries.
The heavyweight aggregate is usually synthetic in nature and may have a typical weight of about
2100kg/m3. Some of the most common types of the heavyweight aggregates are the magnetite,
hematite, limonite, and barite (Linden et al., 2003). Lightweight aggregates are usually sourced
from the manufactured varieties of aggregates. They do have a bulk density less than 1100kg/m3.
Porosity of aggregates

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In between the aggregate particles there exist voids filled with air. The amount of the voids does
determine the nature of porosity of each given aggregate. Besides the air, the voids may also
contain water particles. The size of the voids between the particles does have an effect on the
design process of some construction processes. For instance, those constructions that require
finely divided aggregates do have less amount of pore space. As such, if the coarsely divided
aggregates are used then the resultant outcome will not be effective.
Compaction of asphalt
Asphalt compaction means the process of reducing the air asphalt mixture by means of external
forces thereby making the particles to be more closely packed and arranged (Isenring et al,
1999). Compaction results in an increased density of the mixture. There are various coverage
techniques that are used in the process of asphalt compaction. These techniques include
Initial Compaction by Use of a Finisher
This is done using a low pre-compaction light roller to press the mixture of air and asphalt into a
dense degree. High compaction heavy rollers are not encouraged since they are prone to
damaging the uniformity of the layers. Below is a diagram of the process
Static Compaction

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This process is attained by using the deadweight of the roller and is mostly done using the
pneumatic rollers and the tandem rollers. It has a low effect on the mixture and normally applied
when the initial compaction was low.
Vibratory Compaction
This is a technique used for optimum compaction. It is always applied to increase the
relationship between the density of the mixture and the deadweight (Ahmedzade and Sengoz,
2009). Below is an illustration of how it is conducted
Equipment’s used in compaction

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There are various equipment’s that are used in compaction which includes the tamper, pneumatic
steel roller, and the wheel roller
Tampers
These are machines that are used for compaction in situations where the large compacting
machines have failed are cannot be used (Chang and Meegoda, 1999). They are powered by
gasoline engines
Steel wheel rollers
These are the type of equipment that self-propelled such that they apply steel drum in the
compression of the underlying mixture of air and asphalt. Normally, these rollers pose one or
more drums but not more than three (Appleman et al., 2016). The most common rollers used is
the 2 drum since it is static and vibratory and have a wider range of diameter. Besides, their
weight can be enhanced through a process of compact effort where the wheels are ballasted with
either water or sand
Below is a picture of the steel wheel roller

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Pneumatic wheel rollers
These kind of rollers are also self-driven and they use pneumatic tires in compression of the
underlying mixture of air and asphalt (D'Angelo et al, 2008). They employ tires that are not
threaded on the axles for complete compaction. The tire contains a pressure regulating device
which varies the tire pressure depending on the extent of compaction required. Below is a
picture of the pneumatic wheel rollers
These wheel rollers are most preferred due to some advantages listed below