Where traditional dust suppressants are to be applied in road environments, there are numerous dictating factors that must first be considered.

These include the following:

  • Road surface moisture content during application;
  • Hydrological conditions such as precipitation and appropriate drainage;
  • Mechanical stability of the road surface;
  • Fines content in the wearing course material; and
  • Road base properties and subgrade constituents.

Consequently, the efficacy of common dust suppressants is considered to have a limited applicability in practice.

Along with the application of water, typical dust suppression techniques involve the use of palliative compounds such as lignosulfonates, calcium, or magnesium chlorides. As an example, the different types of road dust suppressants employed in a US State are as follows:

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  • Lignin sulfonate products – 41%;
  • Water – 33%;
  • Magnesium Chloride products – 8%;
  • Emulsified asphalt products – 8%;
  • Calcium Chloride products – 4%; and
  • Other products – 6%.

Lignin sulfonate is a waste product from the paper-making industry. When used as a dust suppression agent, the lignin polymers work by binding soil particles together. When it comes to weather conditions, the applications are only effective under dry conditions with low humidity. There are also significant limitations associated with in situ material; if the wearing course contains little fine material or excessive loose gravel, these dust suppressants are not suitable. As such, although lignin is an effective dust control measure, there are limitations to its applicability.

Water is still one of the most frequently employed dust suppression techniques, even in the developed world. Although water moisture prevents fugitive dust by binding fines to gravel, it must be applied frequently to maintain adequate moisture. At the same time, surfaces cannot be over watered causing road instability. Consequently, although effective, the constant application of water to maintain dust suppression means that it is a labor-intensive process, has high associated equipment costs and has the potential to interrupt general traffic services and work activities.

Magnesium and calcium chloride products have similar effects. Both groups of dust suppressants depend heavily on air humidity level. MgCl2 attracts and retains moisture at a relative humidity equal to or greater than 32% (at 25°C), whilst CaCl2 needs at least 29% relative humidity (at 25°C). The use of magnesium chloride tends to yield a harder surface than calcium chloride. Consequently, it lends itself to more applications in unpaved trafficable surfaces. Both products however, can form a slippery surface when wet, which can jeopardize traffic safety. Furthermore, they are water soluble and thus not suitable for regions with high rainfall events.

Emulsified asphalt is a mixture of asphalt and water that penetrates the soil surface. For efficient application, the asphalt is mixed into the top few centimeters of surface with a grader. The asphalt application causes emissions of volatile organic compounds (VOCs) and contributes to the creation of ground-level ozone and particulate matter, which are the main causes of smog. Additionally, these dust suppressants can contaminate waterways due to runoff and thus are rarely used nowadays.

Although there are many readily available dust suppression methods on the market, there is still potential for vast improvements in the application of products and their relationship with climatic conditions, varying wearing course materials, environmental impacts, road stabilization and driving surface quality. Global Road Technology’s (GRT’s) specialists have succeeded in developing  dust suppression products specialized for driving surfaces. As GRT’s products have a binding property, they also have the ability to contribute significantly to road stabilization. GRT products form flat, stable and non-slippery surfaces. Additionally, are applicable under all weather conditions and in all wearing course types.

GRT Managing Director Troy Adams said dust suppression products also perform well economically. A comparative analysis was undertaken on a 10 km stretch of road whereby traditional watering methods were compared with GRT dust suppressants. After a 3 month trial, the use of GRT products yielded a 40% cost saving over traditional water dust suppression. Additionally, the use of the GRT product also allowed for significant water conservation – up to 99.67% in this case. Furthermore, the transportation and treatment operations required for GRT dust suppression is less than that required by traditional watering, resulting in minimal operational and traffic disturbances.

For more information on Global Road Technology please contact GRT.