Bitumen Specifications and Characteristics
In order to specify the components of Bitumen different methods are used and in most of these methods Bitumen solved in sulfur carbon is divided in three major parts:
- Carbon: the part which is insoluble in tetra chloride carbon
- Asphaltine: insoluble part in solvents such as light aliphatic hydrocarbons such as ether
- Malton: solved part in light aliphatic hydrocarbons such as heptane. Maltons are divided into two minor groups, resins and oils, and while resin materials are brown and semi hard, they provide Bitumen flexibility and adhesiveness. Heavy oils make Bitumen soft, the more its amount the softer Bitumen will be.
The kind and the percentage of the mentioned materials depend completely on the oil or mineral basis of the Bitumen and the percentage of these materials can be changed with the help of their oxidation process.
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Natural Asphalt Petroleum Coal tar Wood tar
______________________ Bitumen |
| | Road tar
Gilsonite Lake asphalt Rock
The amount of Bitumen in rock asphalt (stone Bitumen) is changed from 7 up to 80 percent. In Iran rock asphalt has 70 to 80 percent Bitumen.
In the world more than seven kinds of Bitumen are produced which depends on climate and region conditions, but in Iran Bitumen production is limited to two kinds due to high expenses. At present 85/ 100 Bitumen with high penetration and 60 /70 with less penetration is produced. According to this classification in cold places 85/100 and in warm places 60/70 Bitumen are used.
The Bitumen flexibility makes asphalts lose their resistance in cold and hot climates. In desert regions,
In many countries in order to increase the Bitumen flexibility, polymer is added to it. In this way they increase the flexibility of the Bitumen. The production of multi grit Bitumen in developed countries isn’t an extraordinary or hard affair. They know that for five year Bitumen shouldn’t be repaired or dug, and they increase the life of asphalt to 20 years in this way, and never ignore its repair and maintenance.
Besides Bitumen type, roadbed and preparation of asphalt bed is also important. In making asphalt, 4 to 5 percent Bitumen and 96 percent other materials are used; many of the faults lie on drainage, improper roadbed, neglecting region traffic volume and uncoordinated fulfillment of the project. The method of fulfillment in asphalt section is not according to established principles, and in order to gain more benefit most of the norms are disregarded.