Soil stabilization is essential to build and maintain infrastructure. But with dozens of products on the market, which one should you use? Or, should you choose more than one?
In this blog, we’ll explore the pros and cons of 11 soil stabilization methods to help you decide which one(s) are right for your project:
Lime is a limestone derivative that undergoes chemical changes during processing. It stabilizes expansive soils like clay by reducing swelling and shrinking. Its most common use is for paved road subbases, so soil won’t shift and crack the pavement.
Lime reduces construction downtime and over-excavation by drying and strengthening soil. It can absorb some toxic liquids, so it’s useful for environmental remediation as well.
Lime stabilization impacts the soil’s pH, microbes, and nutrients—which can be good or bad. Getting the right mix of lime into your soil takes work and geotechnical testing. Too much, too little, or the wrong quality produces poor results.
Lime is too costly for most unpaved projects. It also poses health risks that PPE can’t fully eliminate. It irritates people’s eyes, skin, and lungs, and long-term exposure can cause chronic and potentially fatal respiratory illnesses.
Cement stabilization mixes soil, water, and cement. Different projects use different types of cement, although Portland is most common. As cement hardens, it chemically binds soil particles together for a stronger surface. It works well with coarse soils and aggregates, so it’s common for paved road subbase.
Cement is extremely strong. Certain types are water-, chemical-, and weather-resistant, so they last for years.
Compared to other soil stabilization products, cement is brittle and prone to cracking. It requires the right temperature, soil moisture, and mixing process to work properly. And like lime, it’s expensive and often cost-prohibitive for unpaved projects.
Polymers are long, repeating chains of molecules. Most polymer soil stabilizers work like glue to bind soil particles together and improve load-bearing capacity and tensile strength. Other polymers work more like soap: they lubricate soil to make other stabilizers—like compaction—more effective.
Polymers are widely available and work on most coarse soil types. But they’re typically ineffective for fine soils, like clay, because the particles are too small. It’s basically like trying to glue glitter together.
While some polymers for building foundations can last for decades, polymers for road construction often break down within a couple years because they’re susceptible to moisture. Eventually, they need to be replaced. Synthetic polymers are made of plastics, so they can be environmentally harmful.
Magnesium chloride and calcium chloride pull moisture from the air and decrease water evaporation to suppress dust, and they lower water’s freezing point to prevent ice accumulation on roads.
Chlorides also stabilize soil by lubricating aggregates and soil particles so they can move more freely and press closer together during compaction, interlocking and sticking together longer. People sometimes mix calcium chloride with cement, a method that’s effective for combining dust suppression and strength.1
The biggest perk of chlorides is dust control. Dust suppression improves visibility and safety, plus it keeps dust from settling on and damaging property and plants.
Chlorides wash away in rain or snow, so you’ll typically have to reapply them and rework treated roads at least twice per year—especially after the spring thaw. Both magnesium and calcium chloride leach into soil and water. Enough buildup kills plants, pollutes waterways, and corrodes vehicles. Additionally, calcium chloride weakens over time, so soil may collapse.
Between the two, magnesium chloride is “safer,” but we still recommend finding eco-friendlier options whenever you can.
Mechanical soil stabilization relies on machinery to do the work. The two most common methods are compaction and over-excavation.
Compaction applies pressure to push soil particles together, creating a stronger surface. Dynamic compaction repeatedly drops weight on soil, while vibratory compaction uses a roller to “shake” it into place.
During over-excavation, equipment operators dig out unstable soil and keep digging until they hit stable soil or rock. Then, they export the old soil from the jobsite, import new soil, and backfill the excavated area to the appropriate depth. Some contractors add stabilization products like geosynthetics to the imported soil, too.
Compaction works on most soils, has no curing time, and uses no harmful chemicals. It also works best when you pair it with another soil stabilization method, such as Perma-Zyme, since compaction alone doesn’t usually last long-term.
Compaction requires the operator to know proper techniques to achieve best results. Soil must maintain optimum moisture content, so you’ll need water trucks and drivers. Dynamic compaction requires special equipment and disturbs people nearby.
Over-excavation removes and replaces low-quality soils. So, it guarantees that those soils won’t damage your infrastructure because they’re no longer on the jobsite. That’s a win!
That said, the costs of labor and material hauling are high. And if you don’t import the correct new material, you’ve just undone all your hard (and expensive) work.
Perma-Zyme is an enzyme soil stabilizer that chemically reacts with soil particles to bind them together. It strengthens soil up to 13 times and creates a hard, concrete-like surface that resists water and erosion to eliminate potholes, ruts, washboarding, and frost boils. It also significantly reduces dust for up to two years.
Perma-Zyme treated surfaces require little to no maintenance, saving you thousands of dollars over the product’s lifespan. And it’s a long lifespan:
It works in all climates and on a variety of projects—such as solar farm firebreaks, oil drilling pads, mining haul roads, pond linings, and the list goes on. You can also use it to lock in a gravel topcoat to prevent material loss. Perma-Zyme is 100% organic and eco-friendly, so it’s safe to use around people, animals, plants, and waterways.
Application may cost more upfront than some products, like chlorides or gravel, and you must compact the soil fully for optimal results. Perma-Zyme works better with some soils than others, so you may need to import compatible material. (The good news is, paying $0 per year for maintenance makes up for this quickly.) Finally, Perma-Zyme is designed to support traffic and water, so it’s not an acceptable method for stabilizing building foundations.
Aggregates are rocks that people process to certain sizes according to the job the aggregate must do. For example, quarry spalls are large, coarse aggregates favorable for heavy-traffic areas like construction entrances and over-excavation sites. Type II aggregate is a smaller coarse aggregate that’s easy to compact in paved road subbase.
Aggregates are strong, durable, and don’t contain harmful chemicals. Since they’re so common, it's easy to get information about what type and how much you need, as well as how much it’ll cost.
Hauling aggregate is expensive. Choosing the wrong size reduces effectiveness; for example, too fine of an aggregate creates too little friction and makes wet pavement slick and dangerous. Aggregates are dusty, and you’ll have to replace them frequently as they wash away or work into the soil.
Paving a road with asphalt, concrete, or chipseal stabilizes soil and solves maintenance problems unpaved roads face, like washboarding and mud. When it’s not possible or cost-effective to pave a whole road, some county road departments apply a bitumen emulsion, which is a stabilizer spray that mixes tiny pieces of asphalt called millings with water to harden soil.
Most major roads are paved for a reason… because paving works! However, it’s extremely expensive—costing $2 to $3 million per mile for rural roads—and heavy equipment can break pavement down quickly.2 Bitumen emulsions are cheaper, but the millings can be brittle and environmentally harmful.
It’s generally better to pair pavement with an eco-friendly solution. For instance, Perma-Zyme turns native soil into a strong subbase, reducing or eliminating the need for aggregate hauling and allowing for a thinner pavement topcoat. This expedites construction and saves you up to 80% compared to traditional methods.
Geosynthetics are a special type of polymeric soil stabilizer that can be made of fabric (geotextiles), plastic sheets (geomembranes), plastic nets (geogrids), and honeycomb-like containers (geocells). Engineers use different types of geosynthetics to stabilize soil and rocks in all types of projects, from landfills to ground stabilization to avalanche prevention.
Most manufacturers make geosynthetics easy to install with the proper technique. And with so many types of geosynthetics, you can find one for almost any project.
But, installation doesn’t always go as planned. Geotextiles and geomembranes in particular can rip during or after installation, and repairing them is difficult when they’re under an established structure. Some geosynthetics may clog, limiting drainage. And the more complicated the geosynthetics, the more they cost.
Fly ash is a byproduct of coal-fired power plants that works somewhat like cement or lime. This dry powder bonds, stabilizes, and strengthens soil. It also absorbs moisture, so it works well for oversaturated soils. It’s most common in paved road subbase.
The two main types of fly ash are Class C and Class F. Class C hardens when wet, while Class F needs both water and an activator such as gypsum to harden. The type of coal from which the fly ash comes will determine its class.
Fly ash typically costs less than lime or cement soil stabilization, so it can help you stick to your budget. Additionally, using coal’s byproducts eliminates waste.
The downside is that fly ash tends to be less accessible in regions that use less coal. As coal-fired power plants decrease in popularity, this product may become harder to obtain.
Grasses, trees, shrubs, and other types of plants are good for ground stabilization because their roots weave through the soil and hold it in place, reducing erosion. They’re most effective on slopes and in wet areas, where they soak up water.
Plants are the ultimate eco-friendly soil stabilizer. They house wildlife and purify air and water. They’re often cheaper than other methods, and they’re almost always more attractive.
However, you’re limited on where you can use plants—like alongside a road, not in it. Plants are weaker than some man-made solutions. And last but not least, you’ll have to choose species wisely because non-native plants can damage local ecosystems.
Now that you’ve gotten to compare the pros and cons of 11 different soil stabilizers, it's time to decide which one (or ones) will work best for your next project. To sum it all up, take a look at this handy chart:
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