Although bitumen has long been a popular additive used to increase road surface strength, there are disadvantages to its use that must be considered before it is chosen for a soil stabilization project. Usually, asphalt serves as a binder in bituminous stabilization. The type of bituminous soil stabilization technique applied in a given project usually falls under one of these four categories: soil bitumen, sand bitumen, water proof clay concrete, or oiled bitumen.
While bitumen might indeed a good soil stabilization option in many situations, the following disadvantages should be considered to ensure that bitumen is indeed appropriate to the particular needs of a given project:
- Initial reduction in shear strength- When bitumen is used for soil stabilization in saturated soils, it can often temporarily decrease the shear strength of the soil because of the fluid it contains. However, the soil will increase in shear strength as it dries.
- Brittleness- Bitumen has a tendency to become brittle over time. This tendency can weaken the strength of soils stabilized using bitumen. However, this disadvantage is often worked around in bituminous soil stabilization by combining bitumen with other additives.
- Burning risk- In any project where bitumen is used in road construction, there is a risk of burning. This is because bitumen must be added when it is very hot. It must be at least 180˚ C when applied to soil mixtures to function effectively as a soil stabilization additive.
- Environmental considerations- There are a variety of different additives that are considered to be environmentally friendly options for meeting soil stabilization needs. However, bitumen is not considered to be among these "green" alternatives. Soil stabilization methods typically identified as being environmentally friendly include using enzymes, biopolymers, synthetic polymers, sodium chloride, and tree resins.
- Cost- The cost of using bitumen is relatively high in comparison to the cost of using other common soil stabilization additives like cement and lime. For this reason, bitumen is sometimes used in combination with these more affordable materials to keep costs down.
- Limitations in soil types and environments- Great care must be taken when using bitumen to ensure that it is properly used in only the appropriate situations. Bitumen must only be present in stable soils at between 2 and 4 percent. It is best used in hot and dry environments, and it is considered effective in either silty or sandy soils with a 25 to 35 percent liquid limit.
For professional help with soil stabilization, hire professional contractors, such as Geotech Solutions Inc.