dust control and soil stabilization
How do the application methods differ for long-term stabilization vs. temporary dust control?(spraying on a liquid mixture vs. tilling into the soil and compacting.)
Surfactants: As stated earlier these products make water wetter, so that more penetration is achieved. These products will not retain optimum moisture in the soil. Again frequent watering is necessary. They can however be used in preparation for the application of a Binder product or a Hygroscopic product, such as Dust-Off. Dust-Off is attracted to moisture and will penetrate to the pre-wetted depth of the road surface without blade-mixing. We use surfactants to accomplish this task when dealing with hydrofollic soils. The better the penetration of the road surface the longer the benefit of the treatment.Binders: To extend the life of binder type products, blade-mixing them into the soil is most effective for extended benefit or life. Binder type products when blade-mixed into the soil stabilize very well. The short fall is that some of them set up so hard that the road surface will start to crack and pot hole out. This requires a significant amount of time and maintenance to repair. Binder products are usually more expensive and require a significant amount of handling if they are to be applied properly.
Hygrosccpic Products: As stated earlier these products are more user friendly, and easier to maintain. They are usually significantly less expensive. Dust-Off magnesium chloride is a product that works very well in the southwest. Calcium chloride doesn't seem to perform as well in lower humidity conditions, as opposed to the magnesium chloride. Calcium chloride does perform quite well in the wetter climates. The only other short fall of calcium chloride is the corrosion factor. Calcium Chloride is slightly more corrosive than sodium chloride. Magnesium chloride, however is slightly less corrosive than ground water. Dust-Off has an anti-corrosive additive that reduces that to half the corrosion rate of ground water. It is however important that when applying Dust-Off (magnesium chloride) that good practice methods of preparation and application are observed. Of course this holds true with any of the products us. Rain fall will have an effect on these products in various ways. Light rain fall will actually re-activate the product and its ability to hold moisture. Heavy rain fall however will tend to weaken the product, and will cause the product to penetrate on a vertical plane deeper into the surface achieving deeper stabilization. However the surface will need a maintenance application to re-establish the stronger concentration that will continue to pull and hold optimum moisture in the surface, thereby providing adequate dust control.
What are the environmental implications of using these products?
All of these products come with a MSDS (material safety data sheet) which is required by law. I'm sure most all of the suppliers that have been in this industry can provide documentation to support the use of their product in specific applications and in compliance with current EPA mandates. We have an environmental impact study collecting data over a 3 year period and projected over a 50 year model. We also have participated in several monitoring programs, some of them were with the Department of Defense. Dust-Off is manufactured by Cargill Salt, a company that has been around many years. Cargill has taken every precaution to ensure an environmentally friendly product. South Western Sealcoating, Inc. as a supplier and applicator has participated in several of these monitoring programs, including some done with the Department of Defense.
Does storm water runoff from treaded surfaces carry any of the product with it, or are they fairly stable once applied?
This is an issue that should be asked of each supplier about their product. Some of these products do need to be applied in a manner that would preclude any concern in their application. Some may have to be kept an acceptable distance from any active stream beds. Dust-Off (magnesium chloride) has a built in safety factor in this regard. Heavy rain fall causes the product to penetrate on a vertical plane initially. We're talking inches not feet. Migration on a horizontal plane is checked by the amount of water it takes to move the product. Dilution is the safe guard. By the time the product moves from 3 to 5 ft. from the treated area on a horizontal plane the product has been diluted to the back ground level of the native soil. In effect the application of Dust-Off stays within the confines of the treated area.
South Western Sealcoating Inc.
Why choose a stabilization method rather than paving?
Less expensive is the obvious reason, what would be spent in paving a haul road or a county road would be excessive as compared to soil stabilization and dust control methods. As a rule of thumb what would be spent on paving a haul road, construction road, county road, etc. Would provide soil stabilization and dust control for a period of 10 to 15 years. In that same time frame the asphalt paving would require significant maintenance, if not re-paved. Of course storm water runoff is another issue as pertaining to asphalt paving.
What types of sites are these products best suited for?
Soil stabilization and dust control products are suited for any number of projects, from mining haul roads, to county roads, construction access roads, temporary roads, truck or equipment yards, large open areas, such as land fills.
How much traffic can unpaved roads treated with stabilization products handle?
The amount of traffic one of these roads can handle depends on the product being used, the method of application, the application rate, and the type of soil being treated. The preparation of the road prior to application of product is also extremely important. Some of the mining haul roads that we treat have 200 ton haul trucks running on them 24/7. We treat these roads with Dust-Off (magnesium chloride) once with a heavy application and then we will perhaps apply a light maintenance application. The maintenance applications will vary depending on the type of traffic, the configuration of the haul road, and the type of material used to build the haul road.
What Products are available?
There are any number of products that claim success for soil stabilization and dust control or erosion control. They vary form pure vegetable oil to asphalt emulsions, from polymers to surfactants. A couple that have had the most noted success are Lignin Sulfonate, and Magnesium Chloride.
Again the method of application and the rate of application are extremely important. The best approach would be to contact some suppliers with a long track record with a large customer base they have maintained over a period of years. Also ask to see any environmental impact studies around these products. Talk to there customers. Another important factor is the back ground of these suppliers and or applicators. Do they have a background in road construction and soil stabilization, or are they just chemical company's that want to provide there customer's with a product and have the customer do the application.
Brief description of how some of these products work.
These products for the most part fall into three categories:
Surfactants: or wetting agents, detergents, they make water wetter, causing the water to penetrate better and deeper. These products may reduce the amount of water necessary in providing dust control and soil stabilization, due to their penetrating ability. However they do not retain moisture in the soil, so frequent watering is still very necessary.Binders: Dustack Road Binder ( Lignin Sulfonate) These products work very well when blade mixed into the soil, however they don't perform as well with just a topical application. Some methods in applying these products call for dilution of the product in doing a topical application. The theory here is that by diluting the product with water the product will penetrate more. Problem is that product is filtered out with the top ¼ to ½ inch of the soil, the only thing that penetrates is the water. Therefore the more the dilution the more often a topical application is necessary. Again suppliers of these products for the most part try to sell the product to the customer and have the customer do the application. There are various problems with this thinking, the foremost is the lack of knowledge the customer has about how the product works and what makes the product work. Again these products work much better if blade-mixed into the top 1 ½ too 2 inches of the road surface. Hygroscopic Products: Dust-Off (magnesium chloride) These products work very well and are very user friendly, if the right method of application is applied, along with proper preparation of the road surface, and last but not least the concentration and rate of application. These products actually pull moisture out of the air and hold onto the moisture through the heat of the day. Magnesium chloride Dust-Off is an excellent soil stabilizer. The magnesium ions are positive charged, where as the soil is negative charged. The soil that absorbs the magnesium chloride becomes positive charged as well. These now positive charged particles of soil are attracted to the larger aggregate that is still negative charged enhancing compaction. The surface tension is increased and the road surface becomes resistant to the washboarding effect that is often associated with dirt road.