From hiking trails to temporary airstrips, polymer and enzyme soil stabilization products cover a range of needs.

By Janis Keating

Despite all the work done by earthmoving equipment, each year wind and rain move much more soil than man could ever hope to shovel. And because soil is a finite commodity, one has to hold on to as much of it as possible.

Plantings aid in this quest; the roots of trees and forbs help bind the soil, keeping it in one spot. Some spaces, such as dirt roads and trails, however, can't or shouldn't be seeded, so what are the options for holding the soil? Water has traditionally been used on dirt roads for temporary dust suppression, but the oft-resultant mud not only impedes the area's use, it can also cause more eventual erosion - the mud can be carried away on shoes, tires, or treads, and the gullies caused by heavy equipment can collect rainwater and cause washouts. If, as in the case of new home construction, the high-trafficked soil will eventually be planted, the cycle of water-mud-traffic can compact the soil so much that the homeowner will have a tough time getting anything to grow.

Many such problem areas are now being resolved by chemical intervention, with environmentally safe polymers that bind the soil, making it resistant to wind and water erosion. These surface-applied chemicals usually create cationic actions that bind dust particles together, forming a semihard surface that resists wind, rain, and the ravages of traffic.

A Chemical for Every Need

Midwest Industrial Supply in Canton, OH, offers a number of soil-binding products for a variety of applications. Arena Rx, for example, eliminates airborne dust in equine arenas, allowing humans and horses alike to breathe more easily. Diamond Dr is a dust control agent specifically designed for ball fields. Dust Fyghter, a chloride dust suppressant, absorbs moisture from the air and locks it into the soil. Dustract breaks down water's surface tension, increasing the attraction and encapsulation of dust particles. Hydro-Plus, which includes a wetting additive, helps eliminate heat or soil conditions that cause water to drain from seed, fertilizer, or mulch mix.

EK35 uses environmentally friendly synthetic fluids and rosins to provide a dust-suppressing weighting mechanism while acting as a durable, reworkable binder. Designed for intense-use traffic sites (even for tracked and chained vehicles) with heavy powder or surface dust, EK35 does not dry or cure but acts as a continuously active suppressant. The product, which is applied without water, works well with all aggregate materials and soil types.

Soil-Sement, one of Midwest Industrial Supply's most popular products, prevents fugitive dust while providing erosion control. It can be applied to many surfaces and substrates, including unpaved roadways, well-graded aggregates, and clay, silty, or sandy loam soils. The product can also be used on storage piles of coal, minerals, ore, and limestone; on mine tailings, ash ponds and landfills; and on radioactive- and asbestos-containing soils. Soil-Sement can be used in compliance with PM₁₀ air-quality and National Pollutant Discharge Elimination System stormwater requirements.

Sante Tulli, superintendent of Stavola Construction in Tinton Falls, NJ, uses Soil-Sement for dust control in housing development projects. "We spray it onto the soil out of a water truck. It looks like Elmer's Glue when it comes out," he says. "You get a little film atop the soil, which keeps dust to a minimum. You can walk on that film without cracking it.

"We started using it three or four years ago," Tulli continues. "We spray it on housing development pads. If no one drives big equipment on it, it will last eight months to a year. We're very happy with it, and it keeps the area soil erosion people happy."

Desert-Tested

Envirotac 11 is at work in the Middle East for US Operation Enduring Freedom

Environmental Products and Applications in Palm Desert, CA, has offered Envirotac II since 1986, producing more than a million pounds a month for a variety of applications: dust control on landfill slopes, mining operations, freeway shoulders; in power plants on dissipation ponds; and in residential neighborhoods for erosion control.

"It's like liquid plastic. It makes the soil water-resistant; although, when used in smaller quantities, it can be used as a tackifier," describes John Vermillion, the company's president. "It's easy to apply with a [hydroseeding machine] or a water truck." Envirotac II can be added to a hydroseeding mix. "It will enhance the growth of seeds because it bonds with the seed and holds onto the dew to keep the seed moist, to aid in germination. But it won't hold too much moisture, which could make the seed moldy. It holds a certain amount of water but blocks water out if it gets too much."

The product poses no environmental concerns, Vermillion says. "Envirotac II is like a water-based paint - it won't leach and is cured within 12 to 2 hours. Eventually UV [ultraviolet] light breaks it down, and it dissipates into the soil, but by then the vegetation will have grown up. In the case of mining applications, Envirotac II will be reapplied. It holds up one to three seasons, depending on the amount of rain. Other customers spray Envirotac II on coal to keep it from igniting. It's also used for erosion and dust control, like on unpaved roads."

The product was put to an unusual use recently during United States military operations in Afghanistan.

"We donated some to the troops in Afghanistan so they could spray it down on the sand, creating an area where they could land planes and helicopters," explains Vermillion. Envirotac II allowed the troops to create an "instant" airstrip. It doesn't require lengthy cure times (as does cement), and the relatively small amount of Envirotac II required eliminated the need for shipping large volumes of construction materials. It was first used at Camp Rhino, Afghanistan, on November 25, 2001; taking into account the product's viscosity, the US Marines created a colorful name for it: "Rhino Snot."

Suppress That Dust!

The scarifying, application, and compacting process for DirtGlue

From its offices in North Andover, MA, chemical giant Rohm and Haas Company supplies the industry with PaveCryl Suppress, a product that offers dust suppression and road stabilization. According to the company, the vinyl/acrylic emulsion provides optimum penetration and bonding when applied to fine or granular materials such as soil or dust-producing gravel. Treating an area with PaveCryl Suppress results in a durable water-resistant surface.

"Although it's water-resistant, the surface is still permeable," says Anthony Mariniello of Rohm and Haas's Road Construction Chemical Group. "And it is, of course, a water-based product. When applied to a surface at dust-suppression strength, it's like a 'liquid crust.'" At higher dilution levels, PaveCryl Suppress can be used in a hydroseeding mix. "Sunlight eventually breaks it down, unlike MC-70 oil, which never dries and is always in the environment."

Chris Rider, owner of DirtGlue Enterprises in Mendon, MA, offers an anecdote about his product's genesis: "Rohm and Haas originally made the formulation for the paint industry, so paint could be water-based. They found problems with production; the formula wouldn't work with paint, so they used to throw it away. Environmental Products & Applications put it on the ground to suppress dust, and the formula turned out to be better than the alternatives."

Glues Dirt, and Much More

"I learned of this product about 16 months ago and started my own firm," Rider continues. "I'm not exclusively doing slopes and roads; I have even been experimenting with the product for unrelated uses. For example, I recently built an addition to my house and, instead of using tar to seal the concrete before backfilling, I sprayed the foundation with DirtGlue. It went on smoothly, not leaving any air bubbles, as tar can. It dried in 15 minutes, instead of tar's two to three days, and I effectively sealed the foundation, giving it a plastic-type coating. Since I backfilled, it will never be exposed to UV, so it shouldn't break down. I believe DirtGlue's eventual uses will be limited only by one's imagination."

Rider has also used DirtGlue for its original intent. "Many roads in rural Pennsylvania are dirt roads, which get washed out by snowmelt. The state also has 18,000 miles of gravel roads. Pennsylvania offers a Dirt and Gravel Road Program, in which towns get 100% reimbursement for road repair as long as they have state-approved training. One goal of the project is to keep silt and pollutants out of the streams; Pennsylvania wants no more oil going down on gravel roads," he points out.

"Penn State presents agricultural demos, which include new technology, during which about 100,000 people show up for each of the three-day events," he continues. "We did a demonstration, an application at Penn State, putting DirtGlue on farm lanes. To show farmers this indeed could be done easily, we used old tractors from the 1950s, with a manure spreader, to spread the DirtGlue, to 'blow' it onto the road. There were no negative comments with our results. Roads are likely the best application for high-concentration DirtGlue because it contains two different polymers plus a UV stabilizer, so you wouldn't use it at this strength on a slope because it doesn't break down."

For dirt or gravel roads, Rider explains proper application: "First, you scarify the surface. If the use is light parking, you'd scarify maybe to 3 or inches, up to 8 to 10 inches if it's a road at a quarry, for example. Apply this to the entire depth to saturate the soil. Next, grade it when it's wet - very little sticks to the blade. The last step is very important: Compact it, probably with a vibratory compactor, when it's wet. The less air, the stronger the bond."

When he receives his basic mix from Rohm and Haas, it's "50% solid and 50% water," Rider says. "Depending on the application, we dilute it between four-to-one to 12-to-one. It's about the same texture as latex paint and smells slightly like Elmer's Glue before it dries. DirtGlue can be an excellent additive to hydroseeding; wind or water can't erode it, and it acts slightly as a nutrient when it breaks down. We've noticed that birds don't bother it either."

Rider confirms that DirtGlue is safe for the environment. "It's not actually water-soluble but waterborne. It has a high LC50 [lethal concentration in water having 50% chance of causing death to aquatic life] - 50,000 ppm for 96 hours was a lethal dose for trout."

Materials to which the product has been applied can be recycled. "Unlike asphalt, you can reuse the stuff, such as gravel, that's been sprayed with DirtGlue," Rider points out. "In fact, you could probably spray this on concrete abutments, to keep them from spalling from salt. Of course, you'd first have to remove anything loose or moldy. You'd have to give it a maintenance coat once a year, to fill in any nicks or scratches, but the repairs would be virtually invisible and stronger than the original. DirtGlue bonds to itself very well."

A Weapon Against Drought?

According to an abstract published by the Cognis Corporation of Cincinnati, OH, and Duesseldorf, Germany, the company's Terra-Control Soil Stabilizer, a polyvinyl acetate-based formulation, forms a three-dimensional membrane structure that holds seeds and soil in place while allowing water and oxygen penetration (see the article "Environmentally Favorable Erosion Control With a Polyvinyl Acetate-Based Formulation" at www.kiwipower.com/QEI_Atlas_article.html).

Various tests and field trials in the US, Europe, Australia, Malaysia, and Africa revealed that Terra-Control improved soil structure by increasing water and air permeability, the stability of soil aggregates, and infiltration/drainage. The product was also shown to reduce water demand; test plots of lettuce seedlings that received applications of Terra-Control yielded identical plant biomasses to the control groups while reducing water demand between 5% and 50%. Even in Algeria's sandy soil, with temperatures of 35-0C (95-10F), soil saturation was improved 30-0%. 

Other trials with the product revealed that seeds germinated two to five days earlier and that grasses had a higher germination rate (more than 20%). The product also helped retain soil during strong precipitation and despite wind erosion.

With such results, it's clear that chemistry is developing an arsenal against drought.

The abstract also states that no toxic effects against plants, soil bacteria, and fungi are known and that acute toxicity of the primary degradation products of the ingredients is accordingly very low. Toxicity to fish (golden orfe) and Daphina magna (acute, 8 hours) rated an LC50 > 100 mg/l; toxicity to bacteria (Pseudomonas putida) for the same period rated LC0 >10,000 mg/l.

An Enzyme You Can Drive a Truck Over

Nashville, TN's Cypher USA, a subsidiary of Cypher International, produces a similar product, EarthZyme. The multienzyme product was developed as an aid for the workability, mixability, binding, and compaction of soil, improving stability in road, dam, and landing-strip construction. The biodegradable product is suspended in water, and its cationic action binds soil particles together.

When used on unsealed roads, EarthZyme creates a strong, dense pavement. Trials show that when EarthZyme is used, unsealed-road maintenance can be reduced significantly; less dusting occurs, and gravel might last up to two years longer before resheeting is required.

If used on subgrade materials, EarthZyme shows its greatest effect on clay, a soil type that can bond itself into a concretelike material. (Because of the properties of the three main soil types, most chemical intervention products work much better on clay than on sandy or loam soils.) When applied to natural subgrades, EarthZyme has produced California Bearing Ratio increases of 30-0%; -5% increases in density can also be achieved, and reductions in both optimum moisture content and plasticity index can occur. Such improvements in soil strength can reduce the need for the purchase and transport of base gravels. EarthZyme can increase the physical characteristics of lower-quality base-course material with too high a clay content, bringing it to a suitable seal standard.

With so many products available that appear to be environmentally friendly, that can decrease erosion while also decreasing the use of other materials such as gravel, and that might aid in allowing arid soil to flourish and bloom, it's evident that chemical intervention is a process worth considering.

Writer Janis Keating is a frequent contributor to Erosion Control.

EC - January/February 2003