Alchatek Blog

Are you a property owner/manager looking for a geotech contractor to help you with unstable soil, sinking slabs or structures, etc?  As a leading manufacturer of polyurethane lifting and stabilization products, we sell to contractors all over the United States.  Wherever your property is located, we likely know a contractor in your area who can provide an estimate for repairing your geotech problem. 

For a brief overview of the types of services these contractors may offer, see the video below...

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A home or commercial building is only as good as the foundation it’s built on. And regardless of how well-constructed a structure may be, most foundations settle. That’s just a fact of life. Shifting soil compaction and many other environmental conditions that tend to cause settling, however, should ideally be stabilized before significant structural damage is done.

One or two minor hairline or shrinkage cracks shouldn’t necessarily send off any warning bells – though both merit monitoring. But multiple or widening cracks indicate more serious problems and may lead to additional damage. For the property owner, this can disrupt business, displace occupancy, and cause a domino-effect of infrastructure woes serious enough to break the bank. Or worse. Litigation can result if preventative action isn’t taken before loss or injuries occur.

These factors alone make acting sooner rather than later imperative. Stabilization and lifting are key solutions to consider in cases of foundation or slab distress. How can you know for sure if slab lifting or soil stabilization is needed? Watch for these five warning signs:

Bulging or Cracked Floors

It’s estimated that 60 percent of homes built on expansive soils result in shifting and heaving in all or even just part of the foundation. One can’t-miss sign of distress caused by wobbly soil compaction is buckling and bulging wood floors or evidence of cracking concrete in other types of flooring.

Cracked Walls

When soil moisture levels are all over the map, you can be sure that problems will ensue. Poor drainage, soil decomposition, naturally occurring conditions, nearby sewer line damage, underground aquifers – all can play a role in fluctuating soil moisture levels that lead to foundational settling. Cracked sheetrock or concrete walls are a warning sign that trouble is brewing underneath the surface.

Sticking Doors

When doors suddenly start sticking or won’t easily open or close, it’s a sign that either moisture levels are causing the door to swell or something in the structural frame has shifted. And that something might very well be the foundation.

Displaced Moldings

Look up toward the ceiling or down at the floor for moldings that may have gone wonky, jutting this way or that.

Leaning Trees, Fence Posts, Etc.

It’s hard not to notice a tree, fencepost, mailbox, or flagpole that is leaning like the Tower of Pisa. If you don't associate this abnormality with foundational distress, you should. It can be a sign of sinkholes – the kind that gape and maw without warning. If the site you're evaluating is in what is known as karst terrain, which about one-fifth of the nation is, it's susceptible to sinkholes. Likewise if there are abandoned coal or other mines, sewer construction or groundwater pumping nearby. All are signs that further investigation may be needed, pronto.

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When the residue of plants or animals is converted into soil, the process is known as decomposition. Bacteria, fungi, and worms break down this residue, taking nutrients from them and leaving the remaining portion. Organic molecules are broken down into simpler inorganic molecules. This biological process changes the makeup of the soil and can therefore lead to soil instability.

What are the causes of decomposition?

When soil has a high concentration of organic materials, the soil will naturally begin to decompose. Throughout this process of decomposition, the mass and form of these organic materials will change. Up to 90 percent of organic material will actually disappear over the course of the decomposition process, which means the mass of the soil will decrease substantially, reducing the quantity of available soil. The causes of decomposition can be broken into two main groups: manmade and natural. Trash pits or buried construction debris can cause manmade decomposition, while tree stumps and peat content can cause natural decomposition. 

What are signs of decomposition?

Sinkholes, unstable soil, and low spots are all indications of soil decomposition. When soil begins to decompose and shift, it can affect the structural stability of a building, compromising the integrity of foundations and manmade structures. 

How can decomposition be addressed?

In some cases, it is possible to dig up the cause of decomposition. For example, it might be possible to extricate a trash pit or old construction debris from the soil. However, in some cases this simply isn’t feasible. You can’t easily extricate a trash pit after you have already built on top of it. If removal isn’t an option, the best solution is to envelope the area with a high concentration of organic material using expansive polyurethane. This process is known as encapsulation, and it essentially works to compact the area and reduce the amount of oxygen and water that can get to it, thereby helping to slow decomposition.

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What is freezing and thawing?

As the name suggests, freezing and thawing refers to a natural phenomena in which soil freezes in cold weather and then thaws out again once the temperature warms up. Freezing and thawing in northern climates is good news for farmers, as it helps to loosen up the soil and reduce compaction, which makes it easier for crop roots to grow. However, for construction engineers and contractors, freezing and thawing can prove to be incredibly problematic, especially if they are building on fine-grained soils with silt or clay factions, which are more prone to freezing and thawing.

What are the problems associated with freezing and thawing?

Essentially, freezing and thawing cycles accelerate soil instability. Soil with pores containing small particles of frozen water, is known as permafrost. Building on permafrost is fine, as long as the soil stays frozen, but things become problematic once the permafrost begins to thaw. Freezing and thawing of permafrost causes soil to become soft and less compact. Subsequently, this causes structures, such as roadways, railways, foundations, and pipeline supports, to sink. Obviously, this can cause major headaches.

How can the problem of freezing and thawing be mitigated?

Structural polyurethane such as AP Lift 475 can be used to raise settled structures and compact the ground. In addition, permeation grout such as AP Soil 600 is now being looked at as an option to displace water particles in the soil pores. Depending on the soil type, this could prevent frost heave, resulting in a stronger, more consistent base to build on.

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Many types of infrastructure, including roads, bridges, buildings, etc., depend on compacted soil in order to stay in place. Therefore, in order for these structures to last, a specific degree of compaction must be achieved. When soil does not adequately compact, the problem is known as poor compaction, and that can lead to more serious issues. Concrete repair contractors always need to be on the lookout for signs of poor compaction which include settling slabs, cracking foundations, and dips in roadways and railroads.

What causes poor soil compaction?

There are a variety of causes of poor soil compaction. However, much of it boils down to soil texture and soil properties. Some soils are more prone to compaction than others. Excess soil salt content, high clay fraction soils, low pH soils, and soils with high water content tend to compact less favorably. It should also be noted that decisions made by construction contractors and their teams can also influence soil compaction. For example, failure to select proper compaction equipment or compaction materials can contribute to poor compaction. Furthermore, some areas are more prone to poor compaction than others, such as portions of soil set against a foundation.

How can poor soil compaction be corrected?

Luckily, poor compaction can be corrected. The solution is to strengthen the soil to the point that it is properly compacted. As mentioned in the previous post, AP Soil 600, AP Lift 475 and AP Fill 700 are a few products that may be appropriate. Contact Alchemy-Spetec for expert advice at 404-618-0438 if you are currently facing a soil stabilization issue.

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What is erosion?

In geological terms, erosion can be defined as exogenic process that moves a portion of the earth’s crust from one location to another. Exogenic process refers to a range of different processes, including water flow, wind, and even human action, that move dirt, soil, rock, etc. They are called exogenic processes because they originate outside of the earth’s crust, or externally. In more practical terms, erosion can best be described as the way in which the earth is worn away by water, wind, or ice. So when a river carves a canyon out of stone (such as when the Colorado River carved out the Grand Canyon in Arizona over the course of thousands of years), that is an example of erosion. The formation of sand dunes by the wind moving across the desert is also an example of erosion, as are changes in rocks along a shoreline due to the constant thrashing of waves. 

Why does erosion cause unstable soil?

You’ve probably heard that erosion is dangerous because it causes unstable soil. It is important to remember that consequences of erosion can potentially be dramatic, causing landslides and structural damage. After investing money in the construction of a building, the last thing you want is for unstable soil to put the whole project at risk. 

How can erosion be repaired?

Voids can be filled, soil consolidated, and water migration halted by permeating the soil with one of the ultra low viscosity polymer resins in our AP Soil series of resins. Once the bearing capacity of the soil has been increased with this process, then the structure can be lifted if necessary. For example, AP Soil 600 is a one component resin that requires no catalyst. This resin encapsulates and strengthens loose soil, is water tight, and environmentally friendly. Other AP products used in soil stabilization/void fill include AP Lift 475 and AP Fill 700.

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Unstable soil can be defined as soil that will not stay in place on its own, and therefore requires extra support. It should be noted that unstable soil can threaten the stability, security, and safety of infrastructure and can damage, degrade, and even destroy a number of structures, such as buildings, bridges, and roads.

Let's look at the four main causes of unstable soil...

Erosion

Erosion refers to processes in which external elements (wind, water, etc.) remove soil or rock from a certain location and transport it to another location. There are a variety of different erosion types, including river and gull erosion, wind erosion, and erosion attributed to human activity. Erosion ultimately destabilizes soil and can lead to landslides and sinkholes.

Poor Compaction

One of the most common causes of unstable soil is poor compaction. In some cases, certain types of soil are simply very loose and subsequently not compact. The cause of this is typically an imbalance of mineral pieces, organic matter, air, and water. For example, a clay soil with very high moisture content will inevitably become instable, as it will be incredibly difficult to compact. Similarly, soils with high sand content will be difficult to compact.

Freeze/Thaw

Processes of freezing and thawing essentially accelerate erosion processes. Cold weather freezes moisture trapped in tiny cracks. When this water freezes, it expands, subsequently pushing on the rocks and breaking them into smaller pieces. As processes of freezing and thawing continue, rock and sediment are continually broken down.

Decomposition

When soils contain a high concentration of organic materials, such as topsoil and plant matter, it will decompose, subsequently causing it to become unstable. This is because organic materials rapidly change form and mass as they decompose in soil. In fact, up to 90 percent of organic material will disappear over the course of the decomposition process.

Fortunately, stability can be restored to soil with ultra-low viscosity polyurethane resins. Foaming and permeation polyurethanes can mitigate the damage done by processes of erosion, decomposition, and freezing and thawing, as well as help to rectify compaction problems. When it comes to unstable soil, you can’t afford to take a risk. Stable soil is crucial to maintaining secure structures.

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Not all two-component polyurethane lifting and stabilizing foams are specifically designed for wet environments.  In most situations when you are injecting polyurethane foam into the ground, there is a high probability that the environment is going to be wet.  You need to be confident that the foam will react and retain the desired properties in these wet environments.  If the foam you are using is not specifically designed for wet environments, then you may be cheating yourself and your customer out of the best possible results.

All polyurethane foams are going to undergo a density change when introduced to water.  This is precisely because the isocyanate (A component) in polyurethane reacts faster with water than it reacts with the polyol (B component).  Some will undergo drastic changes and some minor changes.  It is important to feel confident that the foam you are using will only undergo minor changes.  The density of the foam is very important because density correlates to foam strength, and you are relying on that strength to support the structure you are lifting or the soil you are stabilizing.

All Alchemy-Spetec products are formulated to achieve minimum density changes when introduced to wet soil.

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Over my many years of consulting with customers on jobs, I have pumped, shot, spilled, splashed, sprayed, poured and injected polyurethane foam into every imaginable type of concrete structure known to man. Most of it has ended up where it was supposed to go. But some of it did not.

Some of it ended up on my clothes, my skin, and my hair. That never bothered me (well, maybe the resin on that brand new button down shirt bothered me a little). What is really frustrating is when it stains the concrete you are trying to fix. Your job is to repair something for your customer, and if you are not careful, you can make it look worse than before.

A few years ago I asked our chemist to develop a water based solvent for cleaning out two component impingement style injection guns (such as our MixMaster Pro gun). I wanted the product to be water based so that it could be dispensed directly into the environment with no negative effects. I also needed it to be thick enough to push reacting foam out of the gun.

After I saw what he came up with, I realized it could probably be used as a barrier to prevent polyurethane from staining concrete. After a little testing and tweaking, I realized it would work.

AP Flush 125 is a concentrated product that you can mix with 3-5 parts water. It can be sprayed onto concrete, wood, metal, or plastic and creates a barrier layer that prevents polyurethane foam from sticking to and staining the surface. You can brush it on or spray it on with a pump up garden sprayer.

Our AP Lift customers spray it right out of the MixMaster Pro gun onto concrete surfaces as they are moving from injection point to injection point. They also saturate cracks and joints that foam may come out of. This has the dual protection of keeping stains off the concrete and helps reduce binding of the concrete that can impede the lifting process.

On hot, sunny days you may have to apply it again if the water evaporates out of the system, but overall it really works wonders. We have used it on lifting jobs, soil stabilization jobs, and leak seal jobs. Now the spray foam insulation contractors are starting to use it to protect surfaces adjacent to their work areas.

Next time you are using polyurethane foam on or near a surface you don’t want your foam to stick to or stain, try a pail of AP Flush 125. One pail of concentrate can give you up to 25 gallons of protection.

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After three decades in this industry, I still find myself in awe of what polyurethane foam can do.  From sealing massive dam leaks to stabilizing airport runway slabs to lifting entire buildings – the feats contractors achieve with this stuff is astonishing.  Yet some people who are new to this technology have a hard time understanding how a mere “foam” can be ideal for these most demanding of applications.  Or maybe they wonder how safe it is. 

The irony is, whether you think you are “new” to this technology or not – you’ve been surrounded by polyurethane all your life.  Sometimes an understanding of the past can provide more confidence for moving forward into the future.  So if you can’t quite grasp how “foam” has been developed to the point that it can lift a building – or you wonder how safe it is – pay close attention to this story.

Dr. Otto Bayer first made polyurethane foam in Leverkusen, Germany in 1937.  Polyurethane was initially used as a cheap replacement for rubber.  Widespread use began in World War II, when many other materials became scarce.  Polyurethane use quickly spread as a key component in many products, from specialized paper to protective military garments to gloss finishes and protective coatings.

In the 1950s, many companies such as DuPont, BASF, Dow, and Union Carbide started producing polyurethane for an even wider variety of applications including adhesives, insulation and foam upholstery cushions.  In the 1960s the Bayer company (no relation to Dr. Otto Bayer) exhibited an all-plastic car, parts of which were made with polyurethane. 

In the early 1970s, the introduction of polyurethane skateboard wheels as a replacement for the old metal ones completely revolutionized the sport, as the new wheels allowed for high impact activities such as jumping off of ramps.  In the 1980s, the first mass produced plastic-body automobile – the Pontiac Fiero – was made with the use of polyurethane technology.

Today polyurethanes can be found in an infinite amount of products including furniture, clothing, shoes, beds, moldings, etc.

In the 1960s, 3M Company in the U.S. and Takanaka in Japan both introduced polyurethane grouts.  3M’s product was called Elastromeric Sewer Grouting Compound.  As the name indicates, it was intended for use in underground utilities.  Takanaka’s product was called Takanaka Aqua-Reactive Chemical Soil Stabilizer (TACSS).  As the name indicates, it was intended for use in soil stabilization projects.  In the early 1980s, DeNeef obtained the rights to TACSS and began distributing polyurethane grout worldwide.  By the mid 1980s, there were almost a dozen manufacturers of polyurethane grouts.  I got my start pumping 3M 5600 to seal cracks in the Atlanta subway system back in 1985.  I was amazed at what it could do back then, and I am still amazed at what our products do today.  3M exited the business many years ago.

In the last few decades, polyurethane grouting has become a widely accepted method for sealing leaks, stabilizing soil and lifting slabs.  Many innovations have been made, including closed cell hydrophobic polyurethanes and the use of two-component foams in geotechnical engineering.  Polyurethane’s advantages over the old school approach of cement grout repair is covered thoroughly in our blog post Polyurethane vs. Cement for Slab Jacking.

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