What is Asphalt? How is it Used?
What is Asphalt?
Nearly all construction materials in Malaysia contain asphalt. If you look closely, asphalt is all around you: roads, pavements, parking spaces, airport runaways, walking paths, driveways, highways. Asphalt has a great variety of uses too. What exactly does Asphalt contain to make it so versatile and important to the construction world around us? Read on to find out.
Simply speaking, asphalt is a mixture of three types of materials: , binders, and fillers. Aggregates comprise processed materials crushed rocks and stones, gravel, slags, and sand. Nowadays, to recycle waste debris and improve asphalt’s sustainability, construction and demolition leftovers (otherwise considered waste), aggregates are also used in asphalt.
Since all the aggregates used in asphalt are basically coarse materials, a binder is used to combine them together in a cohesive manner to form a usable mixture. Most often, bitumen, a viscous black mixture of hydrocarbons derived naturally or as a residue of petroleum distillation, is used as a binder for asphalt. A sticky petroleum by-product, bitumen helps to hold the aggregates together.
Types of Asphalt Depend on the Applications
Depending on where and what the asphalt will be used for, asphalt plant manufacturing facilities vary the consistency and quantity of ingredients in it to create different types of asphalt.
Types of asphalt take their names from the various temperatures at which they are manufactured: hot mix asphalt (HMA), warm mix asphalt (WMA), and cold-mix asphalt (CMA).
1. Hot Mix Asphalt (HMA)
Hot mix asphalt is produced and poured at a boiling temperature between 150 to 180 degree Celsius. Due to its flexibility and water-repellant properties, HMA is extensively used on city streets and highways.
2. Warm Mix Asphalt (WMA)
Warm mix asphalt is the cooler, environmentally friendlier version of its hot mix counterpart. Typically produced at 20 – 40 degrees lower than its equivalent HMA counterpart, the manufacturing process of WMA consumes less energy, thereby reducing up to 75% of fumes emission.
Its lower temperature has a lot of other advantages too. Lower temperature creates more favourable working conditions for the labour and crew. As it cools more slowly than the hot mix, paving activities become easier to handle. Operations where WMA is involved also take less time to become available for use.
3. Cold Mix Asphalt (CMA)
Cold mix asphalt is majorly used for construction surfaces that are exposed to less traffic and load. It is also used for certain winter projects and pothole repairs. As the name suggests, CMA is manufactured without heating the aggregate and the binder.
In the case of CMA, the bitumen is emulsified in water and breaks during compaction or mixing, thereby coating the aggregate itself and producing the final asphalt mixture. As the asphalt settles on the surface, the water evaporates with time and slowly, its strength increases. This makes CMA more affordable and user-friendly than HMA and WMA. It can also be packed and sold as a retail product.
Apart from the three major types of asphalt stated above, there are other, lesser know types used in different types of applications such as:
4. Cut-Back Asphalt
5. Mastic Asphalt
Mastic asphalt finds its application in waterproofing projects. As a mixture of asphalt, stone filler, and mineral powder heated and mixed at high temperature, mastic asphalt forms a dense and durable waterproofing substance.
Hot mix asphalt is used to pave interstate highways and roads that take up frequent, heavy loads. Warm mix asphalt is used on roads in cities and villages where less load is expected. It is also used in tunnels. Cold mix asphalt is used in both cold and warm places for repair works in potholes and cracks.
Cut-back asphalt is used as a stabilizing agent in mixes and sometimes in fog seals, slurry coats, and tack coats. In building construction, mastic asphalt is used as a waterproofing layer for rooftops and storage rooms.
There are other lesser-known applications too where asphalt is used. Builders use it in construction of dams and reservoirs. It is used in public places’ constructions such as parks, walking paths, cycling tracks, and parking spaces.
Asphalt structures are preferred methods of stopping soil erosion. Bitumen based liquid-applied sound deadeners (LASDs) are applied on car bodies to curb vibrations and noise resonance through sheet metal when driving on rough surfaces.