Pavement Preservation Processes – Base Stabilization

Base Stabilization is an effective pavement rehabilitation technique that provides public and private sectors with a strong, durable base capable of withstanding a wide range of traffic loads. It creates an improved homogenous material which utilizes the entire thickness of the existing bituminous layer and a portion of the underlying granular materials thereby reducing material transportation costs and construction durations. Chemical and Bituminous stabilization are two widely recognized realms of the process frequently used world wide.

Bituminous stabilization is accomplished with the use of asphalt or emulsion while

Chemical stabilization is achieved with the addition of lime, Portland cement, fly ash, or calcium chloride.

A wide range of pavement distresses including longitudinal and transverse cracking, rutting, and raveling may be treated by bituminous or chemical stabilization to provide a substantial pavement structure.

Successful construction of the stabilization process starts with concise, well defined tender documents. The following sample tender form and special provisions provides insight on how to initiate the project correctly.

Chemical Stabilization

Although most chemical agents are not prominent in Ontario as sole stabilizers, chemicals provide additional stiffness and life to the effective pavement structure.

Calcium Chloride is a Dust Suppressant and a stabilizing agent that is successfully used on rural gravel roads supplying a strong base for a surface treatment such as a Chip Seal. This combination gives exceptional life cycle cost savings and has been readily implemented throughout Ontario.

The calcium effectively stabilizes the road base by attracting the moisture and resisting evaporation, providing a dense, durable base. The calcium penetrates into the road, coating dust particles and binding them together preventing dust loss to the atmosphere. By reducing dust loss, maintenance costs are reduced and the road integrity is maintained for a longer duration.

Calcium Chloride is applied to the road at a predetermined rate of 3.5 litres per square metre, based upon a 150 mm treatment depth. This total application rate is split into two applications, the first to provide the base stabilization and the second to seal the surface. The individual rates of application for these two steps are 2.5 and 1.0 litres per square metre respectively.

Unlike Calcium Chloride, Chemicals such as lime, Portland cement, and fly ash are primarily used in small percentages in conjunction with a bituminous stabilization process. These chemicals provide additional stability without sacrificing flexibility to maintain exceptional durability.

Approximately 1% by mass of Portland cement is generally incorporated into the Expanded Asphalt mix design to provide additional stiffness, increased Physical Requirements, and fine material to comply with the Gradation Requirements published in the Ontario Provincial Standard Specification for Expanded Asphalt Stabilization (OPSS 331). The cement is applied directly to the surface of the road prior to stabilization and is simply mixed with the Expanded Asphalt treated material.

Lime is generally added in the amount of 1-2% based upon the plasticity index of the in-place material. The addition of lime successfully absorbs the water and effectively decreases the moisture content.

The silica and alumina in Fly Ash form complex cementitious materials.