In general, asphalt is a very viscous hydrocarbon, which occurs in a dark brown to black color, and is produced from the distillation of petroleum. This distillation process can occur naturally, resulting in lakes of asphalt, or it can also occur at an oil refinery that uses crude oil.
Its importance lies in the fact that around 85% of the roads in the world are made with various types of asphalt.
What is asphalt?
Asphalt is a natural or artificial mix in which bitumen is associated with inert mineral matter. It is black or brownish-black in color. At a temperature between 50 and 100 ° C it is in a liquid state, while at a temperature below this it remains in a solid state.
Asphalt is a mixture of inert mineral matter, lime, alumina, lime, silica, etc. and a hydrocarbon known as asphalt bitumen.
In some places the asphalt is available in nature at a depth of 3 to 60 meters. It is known as natural asphalt.
The common variety used throughout the world is the waste asphalt, which is obtained by fractional distillation of crude oil.
Because it is a thermoplastic material, it softens as it heats up and hardens as it cools. It is the basic paving material in use today.
Types of asphalt and its components
Natural asphalt
Also Known As native asphalt. When obtained from lakes it is called lake asphalt. It is used to make pavements, to waterproof structures, to stop vibrations in machine, tunnel and subway foundations, in the manufacture of marine glue and in the lining of trenches.
Rock asphalt
It is a natural rock formation, usually limestone or sandstone, intimately impregnated throughout its mass with 6–14% bitumen.
Refined asphalt
It is obtained by heating the tar to expel the water and extract the mineral matter, segregating the impurities.
Components:
- Bitumen 52%
- Inorganic matter 38%
- organic matter 10%
Mastic asphalt
It is made by gradually adding pulverized natural rock to molten refined bitumen, stirring the mixture for about 5 hours (200–250°), and placing it in molds to cool. The mass consolidates into hard elastic blocks that can be cast when used for paving. It is strong, durable, non-absorbent, moisture-proof, non-flammable and silent. When non-bituminous limestone is mixed with residual-type bitumen, it is brown like synthetic mastic asphalt.
Liquid or residual asphalt
It is the viscous residue obtained by distillation of asphalt-based crude oil at 425 °C.
Cut asphalt
It is derived by distillation of asphalt in a volatile solvent. It contains about 80 percent asphalt and the rest solvents.
Artificial asphalt
It is the pitch residue obtained by evaporation of the volatile component of coal tar. It is formed by a mixture of coal, pitch, ground iron slag, sawdust, chalk, etc.
Composition:
- Bitumen 12%
- Minerals and sand 87%
- organic matter 1%
Asphalt cement
It is prepared by oxidizing asphalt at high temperature, the lighter oils evaporate and are extracted at their condensation temperature, leaving a residual material: asphalt cement. It is used for paving, waterproofing and expansion joints in concrete.
Asphalt properties and characteristics
Below is a summary table that shows the physical, chemical and characteristic properties of asphalt in general, which is used in construction.
| Asphalt | Properties and characteristics |
|---|---|
| Color | Brown, dark gray and black |
| viscosity | highly viscous |
| Density or specific weight | 0.92 to 1.02 |
| Manufacture or origin | Fractional distillation of crude oil |
| water affinity | Does not resist very well in the presence of water |
| Temperature changes and softening | Wide range of hardening temperatures |
| Durability | high |
| Hardening | Slow |
| Toxicity | it is not toxic |
| Solubility | In CS2 (carbon disulfide) |
Asphalt components in general
The asphalt is a construction material which can be separated into five large groups of components, which are characterized by having a great chemical similarity and because they behave in a similar way, they are described below.
- A = Asphaltenes: It is characterized because they are solid materials and because they have the appearance of a powder very similar to graphite but with a coarse grain. They are also dark brown, dark gray and black.
- PC = polar compounds
- A1 = First acidifine
- A2 = Seconds acidifine
- S = Saturates are called “maltenes” and have the consistency and appearance of heavy liquids.
Asphaltenes are soluble only in the presence of polar compounds. The first and second acidifin act as a medium to disperse dissolved asphaltenes and the saturated ones develop the setting characteristics of complete solution.
The ratio of PC / S should be 0.5 or greater to ensure that these components do not separate. The ratio of (PC + A1) / (S + A2) should be between 0.2 and 1.2 to ensure good properties. of aging.
Asphalt uses and applications
The asphalt It is a very interesting material due to its properties, in any case it is used in construction, agriculture, architecture, in the electrical industry and even in automobiles.
Asphalt to build roads
At present the main use and application that asphalt has in the construction industry is to build highways, railways, roads, train tracks and modern bridge fills.
In this case, the asphalt material has the appropriate properties for these applications such as: impermeability, binding capacity, it is weather resistant and provides flexibility to car and airplane runways.
The types of asphalt that are used for roads, tracks and tracks are laminated, compressed rock and putty.
Asphalt paints
In this case, bituminous asphalts are used as special ingredients in certain types of paints, which are basically used for damp walls and also on structures made of concrete.
Asphalt concrete
A certain percentage of asphalt is refined in such a way according to some specifications that give it binding properties, this type is known as asphalt cement and when mixed with fine to coarse aggregates such as basalt to make asphalt concrete.
This type of asphalt is used to pave highways and airport runways, where this material is characterized by its flexibility and resistance over time.
Other uses of asphalt
- Many architects use asphalt in the construction of dams, reservoirs, playgrounds, and parks.
- Farmers use asphalt to line the bottom of retention ponds where they raise fish and in livestock holding pens.
- Asphalt is also an ideal solution for flood control and soil erosion.
- Car manufacturers rely on asphalt to prevent rust and road noise on the fenders and hoods of cars.