Table of Contents
Bitumen is a black viscous mixture of hydrocarbons obtained naturally or as a residue from petroleum distillation or purification. We will discuss the properties of bitumen in this post.
✔ Some of the desirable properties of bitumen are given below.
1. Desirable Properties of Bitumen
A good bitumen should have the following properties:
A good binder must bring all construction materials together and make it a single unit. So, bitumen should be highly adhesive in nature. It should bind materials together properly without affecting the properties of other materials.
Low adhesion leads to the stripping of materials ( like striping of aggregates in the flexible pavement) whereas high adhesion leads to the long life of roads, roofs, etc where bitumen is used.
Impurities present in the bitumen are the biggest reason behind the bad adhesion of bitumen in most cases.
b. Water Proof:
Mainly, bitumen is used in exposed works like road construction, waterproofing, roofing, etc. It has to tackle different climatic conditions including rain. So, it should be insoluble in water and should serve as a waterproofing agent.
Lower water-resistive property leads to lower durability and lower strength of bitumen. It also leads to low adhesion. Hence, bitumen should be highly resistive to the water.
Though mineral or filler materials ( like aggregate ) are the main bearing component; bitumen should also have sufficient strength to resist different live loads ( like wheel load ) & dead loads.
Bitumen should bind all construction materials together for a long time (about 20 years) in adverse weather conditions. For exposed work, it should have a minimum of 10 years of life and for non-exposed work, it should be about 20 years.
Bitumen should show a versatile nature. It must be workable during the construction phase and must be rigid in the operation phase.
Bitumen must be economical to use.
Although the cost of the bitumen depends upon the grade; it should be available at a cheap rate.
The hardness of the bitumen is determined using the penetration test.
In another word, Penetrating depth is the hardness.
The best hardness for different works are:
✔ Hard Coating asphalt – 10 mm penetrating depth
✔ Roofing Asphalt – 15 to 40 mm penetrating depth
✔ Waterproofing bitumen – up to 100 or more penetrating depth
✔ Bitumen should be hard enough to resist the action of loads.
h. Softening Point:
Higher the softening point value, lower will be the temperature susceptibility. So, bitumen with a high softening value is preferred for hot climates.
Ductility is the property of bitumen that permits it to undergo great deformation or elongation.
The value of ductility ranges from 0 to over 150 depending upon the types of bitumen.
Its value also depends upon the temperature, briquette dimension, pulling rate, etc.
j. Viscosity and Flow:
Viscosity should not be very low as well as very high because high viscosity leads to difficulties in the application of bitumen and low viscosity leads to improper binding of materials as it flows fast.
k. Water Content:
The bitumen should contain minimum water to prevent foaming of the bitumen when it is heated above the boiling point of water.
l. Loss on heating:
When bitumen is heated, it leaves out volatiles and causes a loss in mass or weight. So, the loss of bitumen on heating should be minimum.
m. Chemical Resistive:
Bitumen has to tackle different chemicals directly or indirectly (E.g. It has to tackle acids in the form of acid rain).
So, it should be highly resistive against chemicals.
2. Some of the General Properties of Bitumen
Here are some of the other properties of bitumen.
1. It is in solid or semi-solid or liquid states, black and sticky in nature.
2. It melts and gets softened on the application of heat.
3. It has low permittivity and high insulation.
4. It oxidizes slowly.
5. It is chemically inert and hydrophobic in nature.
6. It is insoluble and highly resistive toward the water.
7. It is colloidal in nature.
✔ The quality of bitumen depends upon the grade of bitumen.
✔ High-grade bitumen is durable, hard, waterproof, ductile, and is always resistive to alternate weather, chemical attacks, and many more. They also have a life period of 10 to 20 years.
✔ So, the use of high-grade bitumen should be done on quality works.
|Read More: 18 Differences between Bitumen and Tar|
|Read More: Flexible Pavement|
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