My father had a friend whose response to any question about his general well-being was always “Oh, not so dusty!” by which he meant that everything was bearable and manageable and he would not complain. Keeping our ground “not so dusty” has been a challenge for many years as well, and we have seen different remedies recommended, tried, and used. From talking to those who could suffer in health (and bank balance) from too much dust, it seems we may at last be winning the battle. The solutions are scientific, as they are for many of today’s problems. One of the key words heard is polymer. Few of us are scientists, and we might not be able to come up with a quick definition of polymer, but most of us have heard of the Stone Age, the Bronze Age, the Iron Age, and the Steel Age for the human race; our times may be called the Polymer Age.
A polymer is defined in one dictionary as “a compound composed of one or more large molecules that are formed from repeated units of smaller molecules.” That may not help us too much, but let’s add that polymers have been in nature since the beginning (in such things as rubber, starch, and cellulose). One analogy is that a polymer-based product is like a cake; it combines many little ingredients to make one, big delicious result. Human attempts to create polymers are comparatively new, but they have been most successful and the polymer industry is said to be bigger now than the steel, aluminum, and copper industries combined. Some of the names may be familiar: Teflon, Dacron, Kevlar, polyethylene, and polyurethane. You use plastic bags and containers? They rely on polymers to make them lightweight, strong, and economical. Clothes, packaging, and floor coverings rely on polymers. They have improved the quality and affordability of products as diverse as pipes and adhesives, windshields and insulation, golf clubs and playground equipment. So don’t shake your head in disbelief when somebody tells you polymers may help you solve your dust problems.
While users will naturally have their favorite solutions for dust control, the one fact accepted by most people working on sites where the soil is disturbed is that water can be the least effective and most expensive method. If you live in a community where the summers are hot and dry, you will probably have witnessed an application of water to the ground that disappeared within minutes, leaving the dusty surface ready for the next gust of wind or rolling wheels. The momentum for developing polymer-based solutions for dust control came from the failure of water to satisfy users with areas larger than a few square yards to manage.
Along with the polymer-based solutions we find others, such as those that involve calcium chloride. There have been some that showed promise as dust controllers but have been banned because of their harm to the rest of the environment. In this article we present some dust control products, with comments from their producers about advantages and disadvantages of various solutions. There may be more than one acceptable solution for our dust problems; our homework and research can tell us which is most appropriate. It’s rather like selecting the right brand of vehicle or construction equipment. There are several good choices available and we have the luxury of picking the ones we like.
Emulsions That Bond
“DirtGlue Light polymer emulsion is typically used for soil stabilization encompassing dust control as well as stormwater control, sediment controls, and SWPPPs [stormwater pollution prevention plans],” observes Chris Rider for DirtGlue Enterprises, based in Amesbury, MA. “It functions by bonding the individual soil particles together to prevent them from moving. Erosion control for embankment stabilization is one use, and we have used it for capping stockpiles and controlling sediment to eliminate TSS [total suspended solids] in stormwater runoff.” DirtGlue is a water-based, biodegradable polymer-based emulsion. It is a liquid soil stabilizer designed to protect seed and soil from wind and water erosion. The rates of application will depend on your specific site, of course, but (when correctly applied) it forms a three-dimensional matrix in or on the soil and acts as a semi-permeable, membrane-like structure that can hold seeds and soil in place but still allows oxygen and water to penetrate. DirtGlue is rated as non-hazardous by the EPA.
If there are three priorities for dust control solutions, they are that the products used must be affordable, long-lasting, and environmentally friendly. These priorities are given different levels of emphasis as local regulations are developed or enforced or become more stringent. In some states, for example, many petroleum-based products have been banned because of their harmful effect on neighboring land and waterways. The cost of labor to apply the products is also a consideration that should never be neglected; it affects affordability.
Repairing the damage of wind and water erosion is expensive. “Prevention is a more efficient and economic solution,” notes Rider. “DirtGlue offers a long-term [three to 18 months] and cost-efficient solution for dust control. Our company is a major contributor in our industry’s fight to become more environmentally friendly with less labor costs.” Is DirtGlue, then, just another polymer product? Yes and no. The manufacturer uses a proprietary polymer additive/mix but includes no vinyl acetate copolymers, as some other products do. “Our mix is several times more UV stable and shows excellent low-temperature application characteristics,” says Rider. “It also offers superior flexibility through a wide temperature range. It has much higher adhesive qualities, relative to the copolymers, so it has better bonding capabilities.” From the environmental perspective, the polymer emulsions from DirtGlue are non-corrosive and non-flammable, do not change the pH of the soil, contain no harmful chemical solvents, do not emit any volatile organic compounds (VOCs), and have shown no harmful effect on people, animals, plants, fish, or other aquatic life.
More Emulsions
Increasing environmental consciousness and the growing recognition that labor reduction is a key for business survival led Cognis to the development of Terra Control Soil Stabilizer, a soil-stabilizing polymer dispersion based on polyvinyl acetate. Cognis is an international company with successful projects in places as widespread as Germany, Malaysia, Algeria, Australia, Bulgaria, and the United States. Its US headquarters is in Cincinnati, OH. Terra Control contains materials that are also used as cosmetic and food additives; it is completely biodegradable.
Cognis explains that polyvinyl acetate is a “liquid crust” that strengthens the surface of the soil. It forms a three-dimensional network structure in the upper inch or so of the soil. It fixes seed material to the soil grains and promotes good (often faster) germination, because rain and oxygen can permeate through the crust. The polyvinyl acetate dispersion holds water in the soil longer and protects that soil and plants from rapid dehydration. In a test in Texas, the density of vegetative cover was 24% higher than untreated control (clay) and 67% higher than the sand pot. In France, testing showed resistance to winds of more than 80 mph. (That resistance, of course, will depend on the dosage and correct application!) A dust suppression project that sparked our interest was in Bulgaria, where the product was applied to a waste stockpile. A full vegetative cover was observed only 40 days after the treatment, despite low moisture content in the soil, low rainfall, and high temperatures. The dust levels were reduced immediately after application.
One of the appreciated qualities of Coherex (from Tricor Refining in California) is its stability. It can be stored for long periods without impairing its quality, if kept in clean containers and protected from extreme temperatures. Coherex is a concentrated non-volatile emulsion comprising semi-liquid natural petroleum resins, which form a film to bind the dust, and a wetting solution. The resins are suspended in water and not water-soluble, so the product will not leach out of the soil. This product has shown no harmful effects on plants and animals; it has been used to help germination at such sites as the Los Angeles International Airport. Correct application for each site is important, and the manufacturer will advise users on appropriate dilutions and frequency.
“Coherex provides a modern method for erosion control through proper soil conditioning,” comments Jim Brownridge for the manufacturer. “When it contacts dusty ground, it coats the dust particles and forms cohesive membranes that attach themselves to adjacent particles. This chain-like bond produces large agglomerates too heavy to be dislodged by wind. Treatment with our product is a most effective approach to soil stabilization because the required cohesiveness is imparted to the soil without drastically altering its original makeup.”
Calcium Chloride
It’s the percentage of calcium chloride in the solution that matters. You can find applications for it with solutions from 5% to 45%, with the weight of the solution and its freezing point varying greatly. (At 20%, for example, the freezing point of the solution would be -4ºF. At 32% its freezing point would be -27ºF.) The Dow Chemical Co. (Dow) offers Liquidow calcium chloride in concentrations ranging from 28% to 42%. One of its best known applications is for de-icing, where the 32% is used, but it has been successful for dust control at a wide range of sites, especially on unpaved roads.
Calcium chloride is hygroscopic, meaning it attracts moisture from the air; on unpaved surfaces this keeps the dust down. It also resists evaporation, and that, says the supplier, is why one application lasts such a long time compared with other methods of dust control. Calcium chloride helps bind aggregate particles together, and the chemical actually goes down several inches into the surface to ensure that enemies like frost and traffic wear are less effective. That tends to reduce maintenance costs for treated surfaces.
Calming the Apache Trail
The Arizona Department of Transportation (ADOT) was searching for a new and more economical way to suppress the dust and improve the road safety of a stretch of road once known as the Apache Trail. The department chose Soiltac, a copolymer dust control agent from Soilworks LLC, based in Gilbert, AZ. That’s a beautiful part of the country, and it was no surprise that Daimler-Benz Chrysler chose the area for its Jeep Press Show event. The company wanted to use 22 miles of unpaved road (east of Phoenix and Mesa) along the scenic canyons of the Salt River on Star Route 88. The dust control treatment began near Tortilla Flat, along the dangerous, sinuous, unpaved sections of gravel road that end at Roosevelt Dam. The coordinators of the press event were Event Solutions, and the controlling product was applied by Highland Environmental Control, based in Phoenix.
The road originally went through the Superstition Mountains, linking Apache Junction at the rim of the Greater Phoenix area with Theodore Roosevelt Lake. The trail is traveled constantly by domestic and foreign visitors, with an average daily traffic of 800 vehicles, but, to retain its historic aspect, it remains unpaved. The road consists of primarily decomposed granite and was extremely dusty. Three truckloads of Soiltac totes (14,000 gallons) were brought to the site, and 90,000 gallons of Soiltac dilution were applied. The entire application took two days to complete.
Soilworks is the manufacturer of Soiltac soil stabilizer and dust control agent. It is a liquid copolymer that is biodegradable and safe for the environment, and it can stabilize and solidify any soil or aggregate, as well as provide erosion control and dust suppression. When applied to the soil or aggregate, the copolymer molecules coalesce to form bonds between the soil and aggregate particles. “The key advantage of Soiltac originates in the long, nanoparticle molecular structure that has the molecules linked and cross-linked together,” observes Chad Falkenberg, president of the company. “As the water dissipates from the soil or aggregate, a durable and water-resistant matrix of flexible solid-mass is created. Once cured, our product becomes completely transparent and leaves the natural, native landscape appearing untouched.”
For all these products, you must apply them correctly. Read the instructions, if you’re doing it yourself! Proportions matter significantly. “It is important to know the product and the dilution rates to get the best application possible,” notes John B. Nagel of Highland Environmental, who did the Apache Trail project. “Once that is understood, application can be done with little or no hassle. If not applied correctly, you are essentially throwing money out the window. That is why it makes sense to hire experienced people to do the job correctly.”
The rate of application of Soiltac will determine its final status. For dust suppression and erosion control, modest rates are used to create a three-dimensional cap or surface crust. Heavier rates of application will generate cement-like qualities, useful for the stabilization and solidification found in the construction and maintenance of roads. Adjustments to the rate of application (and Soilworks will tell you how to do this) can make dust control effective for weeks or even months and years.
Sementing the Soil
Soil-Sement is a polymer emulsion from Midwest Industrial Supply Inc., based in Canton, OH, and having almost 30 years of experience in dust control. It’s the configuration of the polymers that gives Soil-Sement its effectiveness. The strength and length of its polymer molecule formulation gives it a chemical structure that comprises molecules attached in relatively straight-linked chains, and then cross-linked among other chains or grids that may be 100,000 molecules long. It’s claimed to be a “true giant” contrasted with the much smaller molecular structure of calcium, oil, petroleum resin, and asphalt emulsion products (which generally range from 100 to 10,000 molecules). The resulting product can be as resilient as rubber or as strong as steel. “Especially today,” says Julie Mamula at Midwest Industrial, “this product emphasizes that all polymers are not made equal. Add to this that we work with each customer to develop a customized dust or erosion control program. We will do complete location surveys, soil evaluations, a review of state and local air-quality regulations and other critical data.” In Canton, Midwest Industrial has more than 160,000 square feet of manufacturing and warehouse facilities, plus satellite operations in other locations of the US, Canada, and Europe.
Longevity is another feature of dust control products that users seek and appreciate. In a test (in Arizona) where there was heavy traffic, both wheeled and tracked, it was determined that the opacity of the dust plumes in the Soil-Sement-treated areas was lower than the 20% required at the property line (after six months) and even lower than that 20% after 12 months. In another test, where this product was tested along with petroleum resins and asphalt emulsions, it was noted that it maintained an effectiveness rating within 10% of the initial application, where the effectiveness of the other types of products dropped considerably.
It has been encouraging research, finding what’s available today for dust control in many different situations. We have not mentioned all we found and you can be sure that there are other solutions, other brand names, on the market, solutions that are, nonetheless, chemical or scientific in nature. At first it seemed nonsensical that water-such an everyday item and so familiar to most people-has become the most expensive solution for most communities. But it is water + something else that is becoming the favorite solution for dust problems. As long as those “something elses” become more and more affordable, long-lasting, and environmentally safe, dust control will be a challenge that every community can face and solve.
