Sept. 15, 2015 09:00

Stick It!

Stick It
That’s so tacky!” When people say that, they usually don’t mean, “That’s so sticky!” Aside from the slang usage, the words ‘tacky’ and ‘tackiness’ don’t really refer to the tastefulness of the pink flamingoes on someone’s lawn, or the bad match of plaids and stripes that someone’s wearing. The meaning actually refers to how sticky something is.

In our world of soil erosion, dust control, soil stabilization and hydroseeding, tackifiers are the sticky stuff that makes soil particles on roads, construction sites or slopes hold together and stay put. They fall under the broad category of adhesives, with applications that run across a broad range of industries.

Some tackifiers come from natural, plant-derived sources, such as guar, starch and psyllium. Many others are synthetic, created in labs. Still others are combinations of plant-derived and synthetic materials. Also, there is some crossover between the tackifiers that are used in dust control and other soil stabilization applications and the ones used in hydroseeding.

For dust control and soil stabilization, the list of spray-on chemical soil treatments, also called palliatives, includes anionic asphalt emulsions, latex emulsions, acrylic polymer emulsions, resin-water emulsions, rosin derivatives, wood derivatives, calcium and magnesium chlorides and soybean oil.

Most of these will be biodegradable; make sure the ones you’re using are.

PAM, short for anionic polyacrylamide, is also used for dust control and soil stabilization, as is guar. These two are the most commonly used tackifiers by hydroseeding contractors.

Guar comes from the seeds of the legume cyamopis tetragonalobus, also called cluster bean. Guar gum, a water-soluble paste, is made from the plants’ seeds, and is a common thickener in foods and drugs. As a legume, it has the added benefit of putting nitrogen back into the soil.

Guar has traditionally been the cheapest and most-used tackifier for hydroseeding. But its price has soared recently, costing as much as 50 percent more than it used to, because the petroleum industry has started consuming a great deal of the supply in fracking operations.

PAM is a nontoxic chemical that’s used not only in hydroseeding, but also for controlling soil erosion and sedimentation on construction sites. It’s been used for many years as a flocculating agent in wastewater treatment and foodprocessing plants, furrow agriculture, mining, petroleum recovery and even personal-care products.

Anionic PAM works by targeting the smallest soil particles, fine silts, clays and colloidal materials as small as five to ten microns in size. It’s safe, effective and economical. There’s another type of PAM, called ‘cationic’ PAM. You probably won’t ever run across it; if you do, just know that it’s highly toxic to aquatic life and should never be used as a tackifier.

In the face of soaring guar prices, a lot of hydroseeding contractors have turned to PAM or PAM-andguar blends.

Cross-linking is an important concept to understand when we’re talking about tackifiers. It’s a chemical process that reduces water solubility and, therefore, increases bond strength and longevity. It makes a relatively weak molecular structure, such as guar has, a little bit stronger and less water soluble, so it can stand up better to rain events.

Randy Hamilton, national sales manager for Profile Products, LLC in Buffalo Grove, Illinois, explains the concept. “Guar, for instance, is slippery when wet, and as it dries, gets sticky. That’s what helps the wood fibers bond to soil surfaces. However, it’s water soluble. Its molecules form long chains that are easily broken apart when wetted.”

“The natural products are less long-term,” said Jim Lange, president and owner of Soil-Loc, Inc., Erosion Control & Stabilization Products, Scottsdale, Arizona. He’s also a soil-erosion contractor. “With the plantago (psyllium) and guar gum, once they get wet, microorganisms can take over pretty fast. They’re meant to hold for a short period of time. The polymers are going to be a lot longer-term.”

Cross-linked guar will last longer through more and heavier rainfall events than straight guar that isn’t cross-linked. Cross-linked tackifiers or combinations of tackifiers are better for steeper slopes, critical sites, and for sites or slopes that could impact nearby bodies of water—places where you just can’t afford to have failures.

Keeping down dust and stabilizing soils

Patrick Stanhope is chief estimator at A-Jay Excavating, Inc. in Atascadero, California. His company does a lot of road dust control and soil stabilization for a major power utility. This utility has hundreds of miles of transmission-line roads that they must be able to traverse in all types of weather, especially inclement.

On many jobs, he turns to a product that is a strong acrylic co-polymer (polymer emulsion). When that’s diluted with water, its long chain of polymer molecules penetrates the soil, forming a strong, hardbound surface.

“The polymer binds the soil particles together,” said Stanhope.

“Once that’s put down, it’s almost as hard as concrete. And if you want to put it deeper into the soil for an even stronger layer of protection, you can rototill it in, and add fiber to it if you’ve got really loose soil.”

This exact method saved the day on a recent power-utility job near Lompoc, California. “All the sand and soil was washing out from underneath a bunch of power poles. There were all these huge erosions, about four or five feet deep. We mixed the tackifier with polymer fibers, blended that into the soil, then compacted it. This tightened everything up and hardened it, and now, the site looks like a highway.”

“For dust control and erosion control, there are different chemical families,” said Bob Vitale, CEO of Canton, Ohio-based Midwest Industrial Supply, Inc. “One family is your polymer emulsions, and various engineered formulas. There are also fluid dust-control products and rosin-based products. We have one that is a combination of rosin materials and a glycerin, and some others that are combinations of rosins and polymers.”

When you’re considering what type of product to use, according to Vitale, there are a number of factors that come into play. You need to ask, what is the exact geological composition of the soil you’re working with? Is it sand, clay, loam, silty loam, sandy loam, a mix of clay and loam? If it’s a road surface, what kind of traffic will be running on it, i.e., what is the weight of the vehicles, and how many tires will they have? How fast will they be going? How well is the road surface presently constructed?

Then, determine the level of control efficiency you wish to achieve.

This may be mandated for you, as many industrial sites already have a certain benchmark in their airquality permits. You might have to keep the dust level under a certain percentage of opacity, say, five or ten percent.

“You shouldn’t think you’re going to totally eliminate dust by using any of these products,” Vitale cautions. “You’ll have to determine the level of control that’s acceptable, and then consider the site factors that are involved. For instance, if there’s an awful lot of spillage by the trucks that will be running on a road you’re treating, you don’t want to expend a whole lot of energy and money to create a wonderfully nice surface that, within a day or a week, is going to be covered up with a lot of that spillage.”

You also need to look at the frequency of application that will be needed. Many of the liquid-polymer products derive an additive benefit from repeated application. “A liquid copolymer should probably be reapplied every three months,” said Lange. “What happens is, once you do your initial application, and repeat it in three months, the next interval might be six months. Each time, it’ll be a longer interval between applications.”

A soil analysis is a critical first step, whether you’re doing dust control, soil stabilization or hydroseeding. “All soils should always have a soil test,” said Sandy House, a technical service associate at Profile Products. “Lots of companies that sell tackifiers and erosion-control products now offer soil testing; we do, and I know lots of others do, too. The analysis won’t tell you what type of tackifier to use, but it will tell you the properties of your soil, and then you can evaluate from there.”

“Lots of the polymer-type tackifiers are mixed with water,” said Stanhope. “So, once they analyze the soil, based on the results, they’ll adjust the mixing ratios for the product you’re going to use.”

There are other reasons why you need to know exactly what type of soil you’re dealing with. For instance, with a mostly clay soil, you can’t get by with just a topical application, as clay doesn’t accept water. “You’ll have to blend in some aggregate base, like a decomposed granite, and then blend the polymer product into that,” said Stanhope.

Clay isn’t as much of a dust issue as is a sandy loam. “Some of your sandy loams can get real silty,” he says. “Those are the ones that are real dust problems.”

Keeping the seeds in place

There are a couple of other plantbased tackifiers used in hydroseeding. One is starch, or amylum, a polysaccharide that is produced by all green plants as an energy store. Starch-based tackifiers retain moisture well through the hydrophilic, or water-loving, nature of their organic polymers. This allows them to both absorb and retain water.

The other is psyllium, the same soluble fiber you might add to your orange juice every morning. Composed of the finely ground muciloid coating of plantago ovata seeds, it dries to form a firm but rewettable membrane that binds soil particles together, but permits germination and growth of seed. It’s a good alternative to guar, as it’s readily available, works well and is inexpensive.

What type of tackifier is popular in your neck of the woods depends partly on climate. For instance, according to House, in many western states, guar, psyllium and starch are mainly used in hydroseeding, because of the arid, warm weather conditions found there.

Kevin Smith, owner of Always Green Hydroseeding in Coventry, Rhode Island, has been spraying seed for the past 11 years. He says that the biggest challenge for him is applying the right tackifier, in the right amount, to get the best holding ability so the seed stays in place for germination.

He adds that in the Northeast, especially in the spring and summer, the skies can open up at any time, and you can get a pretty good deluge. He’s done a lot of experimentation with different tackifiers, with the goal of constantly trying to improve on the ability to keep seed in place.

“I just go ahead and try different products, and see from the results what gives the best holding ability,” said Smith. “I started off using PAM. The polyacrylamide was good, but I learned that it didn’t really act like a tacking agent. What it did was add weight to the mulch, and made it stay in place that way. Currently, I’m using a wood-based mulch, with a polysaccharide tackifier already in it. That seems to be working out pretty well.”

Tackifier has another benefit. When it gets wet, it’s very slippery, so it acts as a lubricant, a ‘slickifier.’ “There are guys with jet-agitation machines that might have weak pumps,” said Doug Holmgren, owner and founder of Turf Blasters, a hydroseeding company based in Sioux Falls, South Dakota. “If they put additional tackifier into their tanks, that helps lubricate the material, and it’ll be less likely to clog their hoses in the mixing process.”

Tim Grenanco, owner and president of American Hydro Seeding in Warren, Michigan, agrees, saying that the tackifier not only makes his slurry slide through his hoses better, but “the slipperiness lets me get more horsepower out of my pumps, so I can shoot farther.”

When choosing tackifier for hydroseeding, cost is just one factor. The location where you’re seeding has something to do with the choice. If you’re spraying a typical, ‘dead flat’ residential lawn with an irrigation system in place, the potential for slope erosion is low, according to Hamilton.

“I always advocate using a guar, versus not,” Hamilton says. “Some people use it straight, with fiber mulch, with no tackifier, even if it’s fairly flat. The only time that might be acceptable is when you’ve got that dead-flat situation with an irrigation system installed, and you have 100 percent control over the water input. So I prefer guar to plantago (psyllium); I just think it’s a better performer. It’s more expensive right now, but it’s a better performer.”

Smith says the most important thing he tells his hydroseeding customers is that he needs to have at least one to two inches of nice, loose soil to work with. “So when I’m spraying the slurry, the tackifier can grab those soil particles and hold them so they don’t move. Then I can really drive in those seeds.”

If the soil is compacted, the slurry will splatter and slide, and you’re not going to get an even application. “It’s almost guaranteed that if you get a heavy rain, everything’s going to slide all over the place.” Also, neither seeds nor roots can penetrate compacted soil very well.

Another soil-related problem Smith has encountered is when he arrives at a job only to discover that someone has thoroughly watered the site. “That’s counterproductive. The ground will resist the hydroseeding, because it’s already reached its saturation point. Everything will just kind of puddle and sit there.”

Premixed or field-blended?

Many hydroseeding contractors prefer to mix their own slurries, putting in their own ratios of mulch, seed, water and tackifier. Others prefer to use premixed mulch blends that already have tackifier included.

“Some contractors are more comfortable making their own special concoctions in the field, and that’s fine,” says Hamilton. “That’s why companies produce stand-alone additives. However, I’m a big proponent of premixed mulches, where everything’s in the bag. That way, there’s no way a misapplication can occur in terms of rate.”

What he’s referring to is that sometimes, the hydromulch application rate can be off, the result of a simple mistake in the field. With a premixed product that includes fiber, tackifier and water-absorbing gels, premeasured precisely by the manufacturers, getting the application rate right is a lot easier.

Hamilton admits, however, that “ninety percent of contractors mix things properly in the field, because they shoot tankloads day after day. They know exactly how much of everything to put in, and could do it in their sleep. But when they’re batching a half or threequarters of a tankload, then it’s easier to goof up on the arithmetic.”

“It’s more convenient using the pre-blended mulch, because it’s already mixed at the right ratio,” says Smith, “and it’s one less step that I have to take when we’re spraying. The rate that we’re using for residential seeding is about 1,500 pounds per acre of mulch.”

Stand-alone tackifier products are available in a variety of package sizes—three or four pounds, 25- and 50-pound bags—tailored for different kinds of hydroseeding trucks.

Doug Holmgren advises new hydroseeding contractors not to be afraid to use a little extra tackifier. “It’ll help things bond better, and make your life easier in the process.”

Smith also believes in taking out some extra tacking insurance. “On days where I know I’m going to get a torrential rainstorm, I’ll take that extra step and add extra tacking agent into the mix,” says Smith. “I’ll add this tacking agent, even though there’s tackifier already mixed in with the mulch we’re using. One of the tacking agent’s advantages is that it has no cure time. It can get wet as soon as you spray it down, and it has the same holding ability as if it got wet the day after it dried. “

He uses a product that contains polyacrylamide flocculants and hydrocolloid polymers that are supposed to increase fiber-to-soil bonding. The bonding agent has the added advantage of not requiring any cure time. It’s a more costly product than regular tackifier, but he considers it “on-the-job insurance, because I know the more I use, the less likely I am to get callbacks.”

Smith says that nowhere is it more important to use enough tackifier than when dealing with a steep slope. He adds that some contractors will double the amount of tackifier they normally use when spraying a slope.

On steep 1:1 or 2:1 slopes, Smith employs a two-step approach. “First, we’ll spray the seed and mulch in a very thin layer, with about half the normal rate of hydromulch. We’ll really drive the slurry deep into the soil, penetrating the dirt as much as two inches.

We want that tackifier to really grab onto those soil particles, and hold those seeds, too.”

“We’ll let that first application dry, and then go back over it with straight hydraulic mulch and more tackifier. I find this holds much better, and keeps everything from sliding down the hill.”

However, too much of a good thing can backfire. Put in too much tackifier, and your slurry can become so thick it won’t shoot. You’ll have to dilute it by adding more water, and maybe a bit more mulch.

There are some other things to be careful about when dealing with tackifiers. Mixing it into the slurry too fast can cause cavitation. The equipment continues to spin around and around, but isn’t really producing slurry.

‘Gumballing’ can result from toorapid mixing. This happens when the tackifier doesn’t have enough time to mix with the mulch, and you find yourself shooting out little balls the size of vending-machine gumballs.

Then there’s ‘overgluing.’ To avoid this, Grenanco doesn’t add extra tackifier to his premixed cellulose mulch that already contains guar. “You can run into a danger with that. If you use too much tackifier, the seeds can’t open; they’re glued shut. You may be able to spray the slurry out okay, but you won’t get any germination.”

He says his cousin, who also has a hydroseeding business, was at first mixing tackifier in separately. When nothing he sprayed would grow, he discovered that ‘overgluing’ was the reason.

As every contractor knows, no matter how much tackifier you use or how good it is, there are still times when you’ll get callbacks. Smith says he can’t guarantee against washouts, because Mother Nature is going to do what she’s going to do. “I’ve learned that if you get a heavy enough rainstorm, with lots of water shear coming off of flat surfaces, there’s nothing you can do to stop it.”

There can come a point where rain isn’t just washing away hydroseed but soil, too. “You can have these big erosion problems. Sometimes you have to replace the topsoil before you can reseed, because everything has just been washed out, including the soil.”

Smith thinks water temperature has something to do with the gumballing process. To illustrate his point, he says, think about what happens when you put sugar in iced coffee as opposed to hot coffee. Which one dissolves faster? “It’s the same here. The colder the water, the longer it takes the tackifier to break down. It doesn’t have a chance to disperse in the mix, and it makes those gumballs.”

How you mix your slurry is just as important as what you mix. Don’t just load everything into the hydroseeder and then turn it on. Instead, have the machine running as you add each ingredient, especially the tackifier.

Without tackifiers, the work of erosion and dust control would be a lot harder, if not impossible. Thankfully, we have lots of alternatives to turn to, and as time goes on, there will surely be more. Here’s to tackiness!

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