Often dust control products are referred to as a dust palliative. This would mean some sort of additive or material that you place on the surface of your road, lot, or yard that provides a dust control.
pal·li·ate
[pal-ee-eyt] verb (used with object), pal·li·at·ed, pal·li·at·ing.
to relieve or lessen without curing; mitigate; alleviate.
pal·li·a·tive
[pal-ee-ey-tiv, -ee-uh-tiv] adjective
serving to palliate.
Dust Palliative Basics
Dust palliatives are substances applied to a road surface to reduce airborne dust. They may be applied every few hours on a busy construction site, or every few years at a site with little traffic. There are many, many kinds of dust palliatives, and many companies produce them. It’s big business, because “fugitive dust” must be controlled at many construction and industrial sites across the nation.
The basic categories of dust palliatives include water, water absorbing products, petroleum based products, organic non-petroleum based products, electro-chemical products, polymer products, synthetic fluids, enzymes, and clay additive products. Many publications describe their characteristics and differences.
Very briefly, the important characteristics separating the different palliatives include:
Occasionally it may seem desirable to use a Bio-Degradable product. However, if you think about it that implies that the treatment is designed to fail as it is supposed to decompose rapidly. (See Definition Below) This should only be desired for especially short term applications.
Types of Palliatives Used
pal·li·ate
[pal-ee-eyt] verb (used with object), pal·li·at·ed, pal·li·at·ing.
to relieve or lessen without curing; mitigate; alleviate.
pal·li·a·tive
[pal-ee-ey-tiv, -ee-uh-tiv] adjective
serving to palliate.
Dust Palliative Basics
Dust palliatives are substances applied to a road surface to reduce airborne dust. They may be applied every few hours on a busy construction site, or every few years at a site with little traffic. There are many, many kinds of dust palliatives, and many companies produce them. It’s big business, because “fugitive dust” must be controlled at many construction and industrial sites across the nation.
The basic categories of dust palliatives include water, water absorbing products, petroleum based products, organic non-petroleum based products, electro-chemical products, polymer products, synthetic fluids, enzymes, and clay additive products. Many publications describe their characteristics and differences.
Very briefly, the important characteristics separating the different palliatives include:
- Is the palliative liquid, or powder. Does it dissolve in water?
- Is a road surface re-workable after it is treated with the palliative?
- When the palliative is applied, does the palliative need to be incorporated into the top few inches of road surface?
- Will the palliative wash or erode away? How soon?
- How frequently will re-application be needed?
- Is the palliative corrosive to equipment or vehicles?
- What precautions are needed in using the palliative?
- Is it hazardous to humans when used according to the instructions? What about if no one reads the instructions?
- As the palliative eventually washes or erodes off the road surface, how does it affect surrounding ecosystems? What does the palliative break down into, and where will it go?
Occasionally it may seem desirable to use a Bio-Degradable product. However, if you think about it that implies that the treatment is designed to fail as it is supposed to decompose rapidly. (See Definition Below) This should only be desired for especially short term applications.
- ‘Biodegradable means that a material has the proven capability to decompose in the most common environment where the material is disposed of within 3 years through natural biological processes into nontoxic carbonaceous soil, water, carbon dioxide or methane.’
Types of Palliatives Used
- Water - Water (!)
- Water Absorbing Products - (Deliquescent Salts) - Magnesium chloride, Calcium chloride
- Organic Nonpetroleum Products - Lignosulfonate, Tall oil emulsions, Molasses/sugar beet products, animal fats, Vegetable oils
- Electrochemical Products - Enzymes derived from food products
- Synthetic Polymer Products - Acrylic Co-Polymers (Styrene, Vinyl), Polyvinyl Acetates
- Synthetic Fluids - Severely hydrotreated, hydrocracked, Hydro-isomerized, high viscosity synthetic iso-alkane
How Do Palliatives Work?
Some Palliatives Work by Increasing Moisture Content
Moisture in the surface of dirt roads causes particles to stick together. The moisture content of dirt roads can be increased either through spreading water or application of salts which attract water.
Though water is available in almost all communities, moving water to unpaved roads can be a problem. Larger communities may have water trucks to take advantage of local water supplies. Smaller communities may not have such equipment. When water can be applied, it only provides a short term reduction in dust. Regular, light watering is better than less frequent, heavy watering.
The application of deliquescent salts to road surfaces can control road dust. A deliquescent salt, like calcium or magnesium chloride, absorbs water from the air. Soils treated with these salts have higher water content than untreated soils. Slippery wet roads and vehicle corrosion are disadvantages of salt application. Also, rainfall eventually removes salts from the roadway.
Some Palliatives Work by Binding Particles Together
This group of dust palliatives includes chemicals which bind fine particles together or onto larger particles. These chemicals fall into several groups, such as petroleum-based, organic nonpetroleum oils, electrochemical stabilizers, and synthetic polymers. When particles are bound together, they can be bound in small clumps or in the case of stabilization level of application, the entire road can be bound together in a solid matrix.
Petroleum-based Binders include emulsified asphalts, cutback asphalt, and Bunker C. These agents coat particles with a thin layer of asphalt increasing particle mass and decreasing the chance of becoming airborne. Emulsified asphalt is a mix of asphalt and water which penetrates road surface dirt. This works well when the asphalt is mixed into the top inch or two of road surface with a grader. These products can contaminate waterways due to runoff and are not often used anymore.
Organic Nonpetroleum Dust Suppressants include lignosulfonates, and resins. Lignosulfonates result from the manufacture of paper when lignin is extracted from wood. Lignin is a natural polymer and can bind soil particles together. Lignin occurs in solution with sodium, calcium, ammonium, or magnesium bisulphate. Resins made from combining lignosulfonates and additives can neutralize adverse effects. Lignosulfonates are water soluble and can move out of, or deeper into, a roadway surface with rainfall. These products corrode aluminum unless calcium carbonate is present. Lignosulfonates work best with fine dusts such as clay particles having a high plasticity in dry environments. Glacial tills typically have low plasticity. Lignosulfonates may be of limited value in controlling dust in Alaska.
Electrochemical Stabilizers include sulphonated petroleum, ionic stabilizers, and bentonite. These products neutralize soils that attract water and allow bonds to form between particles. Electrochemical stabilizers need to be worked into the road surface, requiring equipment that may not be available in remote rural communities.
Synthetic Polymer Products and Synthetic Fluids include polyvinyl acrylics and acetates, and high viscosity synthetic iso-alkanes. They bind soil particles and form a semi-rigid film on the road. These products are either liquids or powders that are mixed with water. Products are applied in liquid form and require drying. Temperatures during the curing should not approach freezing. Traffic should be diverted from treated areas until after drying - which can take 3-24 hours depending on temperature and humidity.
When selecting an acrylic co-polymer such as MaxxSeal 100 or MaxxSeal 200 you can choose application rates to provide anything from short term dust control to long term dust control or even soil stabilization to provide improved road strength up to 7 times the normal potential strength. (See Chart) This is when your road has been transformed from a loose aggregate material into a solid matrix with entire surface bound together.
Some Palliatives Work by Increasing Moisture Content
Moisture in the surface of dirt roads causes particles to stick together. The moisture content of dirt roads can be increased either through spreading water or application of salts which attract water.
Though water is available in almost all communities, moving water to unpaved roads can be a problem. Larger communities may have water trucks to take advantage of local water supplies. Smaller communities may not have such equipment. When water can be applied, it only provides a short term reduction in dust. Regular, light watering is better than less frequent, heavy watering.
The application of deliquescent salts to road surfaces can control road dust. A deliquescent salt, like calcium or magnesium chloride, absorbs water from the air. Soils treated with these salts have higher water content than untreated soils. Slippery wet roads and vehicle corrosion are disadvantages of salt application. Also, rainfall eventually removes salts from the roadway.
Some Palliatives Work by Binding Particles Together
This group of dust palliatives includes chemicals which bind fine particles together or onto larger particles. These chemicals fall into several groups, such as petroleum-based, organic nonpetroleum oils, electrochemical stabilizers, and synthetic polymers. When particles are bound together, they can be bound in small clumps or in the case of stabilization level of application, the entire road can be bound together in a solid matrix.
Petroleum-based Binders include emulsified asphalts, cutback asphalt, and Bunker C. These agents coat particles with a thin layer of asphalt increasing particle mass and decreasing the chance of becoming airborne. Emulsified asphalt is a mix of asphalt and water which penetrates road surface dirt. This works well when the asphalt is mixed into the top inch or two of road surface with a grader. These products can contaminate waterways due to runoff and are not often used anymore.
Organic Nonpetroleum Dust Suppressants include lignosulfonates, and resins. Lignosulfonates result from the manufacture of paper when lignin is extracted from wood. Lignin is a natural polymer and can bind soil particles together. Lignin occurs in solution with sodium, calcium, ammonium, or magnesium bisulphate. Resins made from combining lignosulfonates and additives can neutralize adverse effects. Lignosulfonates are water soluble and can move out of, or deeper into, a roadway surface with rainfall. These products corrode aluminum unless calcium carbonate is present. Lignosulfonates work best with fine dusts such as clay particles having a high plasticity in dry environments. Glacial tills typically have low plasticity. Lignosulfonates may be of limited value in controlling dust in Alaska.
Electrochemical Stabilizers include sulphonated petroleum, ionic stabilizers, and bentonite. These products neutralize soils that attract water and allow bonds to form between particles. Electrochemical stabilizers need to be worked into the road surface, requiring equipment that may not be available in remote rural communities.
Synthetic Polymer Products and Synthetic Fluids include polyvinyl acrylics and acetates, and high viscosity synthetic iso-alkanes. They bind soil particles and form a semi-rigid film on the road. These products are either liquids or powders that are mixed with water. Products are applied in liquid form and require drying. Temperatures during the curing should not approach freezing. Traffic should be diverted from treated areas until after drying - which can take 3-24 hours depending on temperature and humidity.
When selecting an acrylic co-polymer such as MaxxSeal 100 or MaxxSeal 200 you can choose application rates to provide anything from short term dust control to long term dust control or even soil stabilization to provide improved road strength up to 7 times the normal potential strength. (See Chart) This is when your road has been transformed from a loose aggregate material into a solid matrix with entire surface bound together.
Advanced thought on the desired end results is very beneficial in making your ultimate decision regarding the best product for your project.
Ref – Dust Palliative Basics – Alaska Department of Environmental Conservation
Advanced thought on the desired end results is very beneficial in making your ultimate decision regarding the best product for your project.
Ref – Dust Palliative Basics – Alaska Department of Environmental Conservation