Sept. 16, 2016 01:46

Tackifiers

tackifiers_soilerosion

Likes and dislikes are a funny thing. Virtually everyone likes candy; it only starts getting interesting once you ask what kind of candy someone likes. Take coconut, for instance; people either love it or hate it, with no in-between. As for myself, once I detect a flake if coconut in something, I'm immediately repulsed. If I may mix metaphors for a moment, it feels like fingernails on a blackboard to me. Oddly enough, I love the flavor of coconut, I just can't stand its texture.

You as a contractor also have favorites when it comes to the tools and products you use to do your work. Though a much less trivial matter than picking a candy bar, you arrive at these preferences in a similar manner, by trying things out and seeing how they ‘taste.’ Over time, you discover what works best for you in the applications you use them for, is the most cost-effective, and causes the least amount of hassle. That is what you’ll use.

So it is with tackifiers. There are lots of good ones out there, but not everyone who does hydroseeding, soil stabilization or dust control work uses the same ones. Some contractors love guar, while others prefer plantago; many more swear by the anionic polyacrylamide (PAM) formulas. No matter what these professionals use, they all have good reasons for their preferences, based on experience, and the way these materials behave.

Let’s start with guar. It’s derived from the seeds of the cluster bean plant, formally named cyamopis tetragonalobus, and is usually imported from India, where the conditions are right for growing it. It’s processed into a water-soluble paste called guar gum that’s also used as a thickener in foods and drugs. Slippery when wet, it gets sticky when it dries.

Guar was the next tackifier hydroseeding professionals turned to after they were forbidden to use asphalt. As a natural product, guar is environmentally benign. And, because it comes from a legume, it puts nitrogen back into the soil. For many years, it was the cheapest and most-used seed glue, and the preferred one for tacking straw. It was in short supply for a while, but it’s once again abundant and fairly inexpensive.

You’ll often hear about “crosslinked guar.” Crosslinking is a chemical process that reduces watersolubility, increasing the plant derivative’s bond strength and longevity.

Since guar has a relatively weak molecular structure, forming long chains that are easily broken when wetted, crosslinking gives it a greater ability to withstand rain events, even prolonged, heavy ones.

Tackifiers or combinations of tackifiers that are crosslinked are better for steeper slopes and for areas where a failure could result in sediment or pollutants entering bodies of water.

Plantago is another plant-based tackifier, made from the ground-up protective coating of the plantago seed, also known as psyllium. Good for stabilizing soils, plantago is used in both hydroseeding and dust control applications.

Anionic polyacrylamide (PAM) is a biodegradable chemical that’s also used in controlling dust and stopping sedimentation flows on construction sites. Wastewater treatment plants use it as a flocculant to remove pollutants.

Guar, plantago and PAM are the Big Three tackifiers used in hydroseeding applications. “The trend over the last eight or ten years has been towards PAM,” said Ray Badger, CEO of Turbo Technologies, Beaver Falls, Pennsylvania. “It seems to be taking over, probably because it does as good a job as the other tackifiers, costs less, and you need less of it.”

“Three pounds of PAM will treat an acre that would require 30 pounds of guar.” In his opinion, PAM is also a bit better at holding slopes.

The EPA considers PAM safe to use. Despite this, there is some debate as to whether or not it’s harmful to marine life. This may be a result of confusing anionic PAM with cationic PAM.

Anionic PAM is the type that’s used in hydroseeding and dust control, and is considered to be environmentally safe. Cationic PAM, on the other hand, is known to be highly toxic to aquatic life. You probably won’t run into the cationic variety, but it’s important to know the distinction.

Jim Scales, owner of Mid GA Hydroseeding, LLC, in Gray, Georgia, uses a combination product that has “a little bit of everything” mixed in. “It a guar gum type tackifer, with PAM mixed in. The polyacrylamides are great for soil stabilization, better at holding the mulch on the soil. And the guar gum binds the mulch together.”

It’s a case of the team being stronger than any single member. He finds that combining the properties of the two tackifiers works better than using either one of them by themselves. “If you just use guar, it’ll hold your mulch together, but won’t hold it to the ground.”

The natural tackifiers tend to be cheaper than PAM. Currently, a 50- pound bag of plantago can be had for around $25; PAM runs around $180 for that same amount. Guar, at the height of the shortage, was $120 per 50 pounds, but has since dropped below $100.

Erik Burr, owner of TerrawoRx, LLC, Albuquerque, New Mexico, likes plant-based tackifiers for a very specific reason. “We use a blended, plant-based combo, (our own formula), in our hydromulch. Once the tackifiers start to break down, they become a food source for the beneficial microbes, which in turn, makes the plant material healthier.”

There are several options for utilizing tackifiers in a hydroseeding application. A contractor can mix it into his seed, mulch and fertilizer slurry separately. Or, he can buy mulch with the tackifier already in it. Still another approach is to spray the seed, mulch and fertilizer first, then apply tackifier over it in a separate operation. If straw is used over the seeded area, the tackifier is sprayed over the straw.

Is it more advantageous to use a premixed mulch blend, or to add tackifier separately? Badger said that using a premix would save you a step, but can be more expensive. If you add the tackifier separately, you can vary the amount based on the steepness of the grade on the job you’re doing.

“If you’re doing something fairly flat, you can add less. But if you’re working on a site that’s fairly steep, the steeper it is, the more I would add. Adding tack separately gives you more control over that.”

However, many state DOTs don’t allow you to field-mix tackifier. The rulebook will say, “Hydromulch must be pre-blended by the manufacturer.” Matt Welch, technical manager at Profile Products, LLC, Buffalo Grove, Illinois, says it’s a quality control issue; the agencies kept running into situations where too little tackifier was being used.

Many manufacturers make their own tackifier formulations. “We make a custom blend that combines PAM, guar and psyllium,” said Badger. “It’s got the same amount of PAM in it as a straight PAM tackifier; but sometimes PAM can form gumballs. These other ingredients seem to keep it from doing that.”

Polyacrylamide does have a tendency to form little marble-sized balls, sometimes as a result of mixing slurry too fast. Or, dumping your PAM all at once into the mix; once it hits the water, the gumballs can start forming instantly. Why does this happen? Since PAM contains charged particles, it wants to form bonds with other charged particles. Adding it in slowly should prevent this issue.

At any rate, Badger says gum balling isn’t a serious problem, as he’s never heard of it causing a hydroseeder to clog. The issue can be avoided entirely by using a preblended hydromulch that already contains tackifier.

Both PAM and guar act as lubricants, but PAM lubricates more than a guar-based tackifier will. If you put your hand in a mix that has PAM in it, you’ll feel something between a slimy and a slippery feel, like soapy water, but stickier.

Phillip Kelly, owner of Affordable Hydroseeding in Wasilla, Alaska, appreciates this aspect of PAM. “I like that it creates a slippery slurry. Because it slides through the hose a little bit easier, I’m able to make my hydroseeding batches a little bit thicker. I can spray with a decent amount of force, and still be using my materials efficiently.”

The thicker slurry allows him to spray bigger areas, and still get proper coverage. It also holds up better on the steeper slopes.

Some contractors like to add a touch of extra tackifier as a kind of “insurance,” especially when dealing with very steep slopes. Be careful about doing this—add too much, and you could actually glue seeds shut. They may spray out, but they won’t germinate.

Contractors in Alaska are much more dependent on what’s available from local suppliers because of the high cost of shipping. Kelly says the place he gets all of his materials from no longer sells guar. That’s fine with him, because he doesn’t think he’ll ever want to use guar again.

“The stuff is kind of hard to handle, at least when I last bought it, because it came packaged in paper bags. If you accidentally got the bag wet, it clumped up and made a sticky, gooey mess, and you had to throw it out.”

The tackifier he uses now is an anionic linear copolymer of acrylamide in the form of scoopable crystals that can be used with any paper or fiber mulch products—and it comes in a plastic bucket.

He finds that he needs less of it to do the same jobs. “If I was still using guar, I’d need to carry more of it, and I only have so much weight capacity and space on my truck. If I can reduce the weight and volume of the materials I’m hauling around, that’s better for me.”

Does weather and humidity affect tackifier? “No, not so much,” said Scales. “But, if the ground is already wet from rain, you can go a lot further with your mix. The tack helps lock the moisture in a little bit better, and that’s important, because down here in Georgia, the dust just eats you up. Your hydromulch can just sort of roll up in it, and you have to spray more and more material to get the coat you’re looking for.”

Other contractors say that ground that’s already wet can be resistant to hydroseeding, as it has already reached its saturation point.

Dust control

There’s a long list of dust control and soil stabilization treatments, including PAM, latex emulsions, resinwater emulsions, pine rosin, lignin sulfate, calcium and magnesium chlorides and even soybean oil. Plantago is sometimes used as well.

Adam Bappe, a technical sales representative at Triton Environmental’s Commerce City, Colorado headquarters, says he’s always being asked, “What’s the best tackifier for dust control?” First, he says, you need to ask yourself some questions, such as: “How long do I need it to last?” “How much am I willing to spend?” “Am I treating a road that’ll be driven on?” “What’s the source of the dust, a construction site or an ash pile?” “You can use plantago and get yourself a month of longevity. If you need something that’ll last two or three years, you’ll need something more expensive.”

For long-term dust control on high-traffic roadways, the polyacrylamides are probably your best bet.

Once the natural tackifiers get wet, microorganisms start the biodegradation process. Plant-based tacks should only be used for short-term situations.

A periodic reapplication of PAM will probably be needed, especially in a long-term or high-use situation. Luckily, the effect is cumulative. The first repeat coat should be laid down after three months, but you can wait another six months after that to do the second one.

Obtaining a soil analysis is particularly important when you’re doing dust control, and especially when you’re using PAM tackifiers. They’re usually mixed with water, and the mixing ratio depends on the type of soil you’re going to be applying it to.

The texture of the soil is an important consideration. “If you have a very sandy soil, a polyacrylamide’s not going to do much for you, because it’s designed to bond with electrically charged particles,” said Welch. “But sandy soil doesn’t have a lot of charge to it. That’s why clay lumps together better than sandy soils will, because of the charged particles.”

Clay tends to be hydrophobic, or water-repellent, so a surface application probably won’t work. A better approach there is to get some aggregate, such as broken granite, and blend the PAM into it.

There’s no single tackifier that’s perfect for every single hydroseeding, soil stabilization or dust control application. What you choose will be determined by price, convenience, and availability, along with your own personal preferences based on experience with them in the field. Could the future possibly bring new tackifiers to the marketplace? All we can say to that is, “stick around!”

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