Chemical Stabilization

Chemical agents are becoming extremely popular within the recycling industry as sole stabilizers and as inhibitors for both cold-in-place reclycing and expanded asphalt stabilizaiton.

Magnesium 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 magnesium chloride effectively stabilizes the road base by attracting the moisture and resisting evaporation, providing a dense, durable base. The magnesium 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.

Magnesium 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 Magnesium Chloride, chemicals such as lime, Portland cement, and fly ash are primarily used in small percentages in conjunction with a bituminous recycling process to effectively increase the pH of the aggregate facilitating a stronger bond between the bitumen and aggregates. 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 increase the Physical Requirements and the filler content 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.