Asphalt is an essential raw material for making pavements and walkways, and has been so since decades. The finished material used for pouring on pavements is also known as asphalt concrete due to being a mixture of fresh asphalt and filtered aggregate. Asphalt sales in US have significantly improved over the years due to increased pavement renovation projects and new construction. With a total revenue of $26 billion, asphalt manufacturing industry and asphalt sales industry remains a significant contributor to the US economy.
Asphalt can be made into different variants depending on the soil type, usage pattern and applicable conditions where the asphalt base is to be installed. Asphalt cement retains the same properties and is constant, and so is the aggregate. What makes these variants different is the difference of ratio of mixtures of components, and the method of mixing, such as heating, direct mixing or addition of external accelerators to give the asphalt some special properties depending on requirement. Common variants of asphalt used throughout US are:
Hot Mix Asphalt
Hot mix asphalt is a
combination of asphalt cement and aggregate that are uniformly mixed and applied.
In this case, both the aggregates and asphalt cement are heated prior to mixing
to ensure that asphalt cement sticks properly in the gaps between aggregate,
hence giving rise to the term hot mix. Hot mix asphalt is more effective when
mixed on-site, which is then applied directly to the pavement. It can resist
all kinds of weather, and snow melts faster on hot mix asphalt pavement making
it perfect for use in chilly areas. It can also expand and contract without
breaking, making it suitable for use in warmer areas such as Midwest as well.
It is usually built for high traffic pavements such as freeways and airport
runways.
Warm Mix Asphalt
Warm mix asphalt has a
distinct advantage over hot mix asphalt: its significantly lower drying time,
which makes it suitable for usage in time-constrained scenarios when pavements
need to be built quickly. Various mixtures such as zeolites, emulsions and
waxes are often mixed to regular hot asphalt to produce warm mix asphalt. The
asphalt cools of very quickly, resulting in the term warm mix. It is used for
construction of regular pavements and high traffic pavements. The ability to
add different additives means the finer properties of warm mix asphalt can be
modified depending on usage scenario, such as added strength or durability.
Cold Mix Asphalt
Cold mix asphalt does
not require heated aggregates or asphalt cement; they are directly added and
ground together. Cold mix asphalt is usually suitable for small scale
applications or temporary scenarios, such as repairing a patch of pavement or
mending cracks and potholes. They are avoided on roads with high traffic due to
low durability. The quick application time of cold mix asphalt means it is
perfect for usage as a quick fix to any existing pavement damages.
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