Alchatek Blog

Are You Smarter Than a Fifth Grader?

Jeff Foxworthy often asks if you are smarter than a fifth grader. Well if you're not, don't worry about it; you're probably still capable of estimating the amount of foam needed to raise a concrete slab. Through a combination of easy calculations, product information, and some site considerations, you should be able to estimate your slab lifting materials without too much trouble.

First of all you need to think about the basic volume calculation. How many square feet of slab are you jacking, how much do you need to lift it, and is it the whole slab being lifted or is it just one end of it? Calculate the volume (length x width x depth), adjust for the percentage of the slab being lifted, then compare it to the expansion properties of the injection foam in order to determine how much you need.

Beyond the geometry required to estimate lifting the slab, you must now take into account some job specific considerations. This is where it becomes critical to qualify the volume of material included in your proposal. And just as important, this is where you need to make sure you have included enough so you get the job done right and don't have to go back to the customer asking for more money. Sometimes that's unavoidable if you encounter surprises; but if you keep a few considerations in mind this can often be avoided.

Soil Compaction

Isaac Newton's third law of motion determined that for every action there is an equal and opposite reaction (or was that Wayne Newton, ha?). If you are trying to lift a slab, a porch, or a pool deck on ground with poor compaction or water issues, the foam will compact the soil until it is dense enough to support lifting the slab or deck. And the heavier the object, the more densely the ground will have to be compacted. Make sure to measure the soil conditions (using a penetrometer or probe) and adjust your material estimate accordingly.

Size / Shape of the Object Being Lifted

Extremely heavy objects can be lifted with polyurethane foam using a small amount of pressure and material. Often times the most difficult lifts are the smaller objects. Something with a small footprint, like some front steps or a stoop can be very dense and frustrating to lift. Injected material is going to seek the path of least resistance until it is contained enough to generate the lift. For a front stoop, the path of least resistance is usually going to be out the sides; meaning lost material and more cleanup. Proper injection techniques can contain the escaping material, but it is advisable not to underestimate your material on an innocent looking small job.

Voids

Sometimes the ground can be well compacted but due to erosion factors (usually misdirected water runoff) slabs and other foundation type settlement can occur. Although the object has only settled a few inches, sometimes a much deeper void can be hidden from view. In these cases it is advised to use a probe through a hole drilled in the slab in order to get an idea of the depth of the void. Personally I have seen voids that went down 20 feet, so do not ever assume anything. Most void depths are pretty easy to determine and you will get the optimum expansion out of your material when filling them. But once again, calculate the extra volume to fill it and spell it out in your proposal.

Typically for a lifting job with no other considerations aside from lifting volume, we recommend adding an additional 10-15% onto your material estimate to cover yourself. Just make sure you do a thorough evaluation of the conditions and possibilities so you don't underestimate the job and have to go back to the property owner with your hand out. 

If you haven't already, make sure you read this blog post on our custom Alchemy-Spetec material estimating app for your smartphone.

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Any successful slab lifting job begins with a thorough site evaluation. Some new jobs are like previous jobs, some are a little bit similar, and many are a completely new experience altogether. A site evaluation is not limited to, but should include Identifying the Cause of Slab Settlement, Gathering Information, Identifying Potential Hazards, and Visualizing the Mobilization.

Cause of Slab Settlement

Determining the cause of settlement is usually the first step in beginning your evaluation. The cause can be any number of things such as erosion, ground water, sink holes, poor compaction, and buried debris that breaks down over time. Correctly identifying the cause will help you determine if slab jacking alone will solve the problem or whether a combination of lifting, stabilizing, and / or void filling will provide the permanent solution.

Gathering Information

The next phase should include gathering information from multiple sources. This includes dimensional information such as length and width of the slab; but also, the amount it has dropped, to help determine the volume of structural foam needed to lift the slab back into place. Make sure to bring your camera, notepad, and tape measure. Gather information from the property owner; find out about any known irrigation, electrical, water, or drain lines. Specifically, find out from the owner about any areas or features that need protecting around the injection site, the location of your rig, and all points in between where your crew may be working.

Identifying Potential Hazards

If the job is outside of a building, find out where the utilities are and have them professionally located. It's a lot harder to get paid when you have just drilled through the owner's power line or filled his landscape drains and fountains with foam. Additional information that may be available could include a soil engineering report, a structural engineering report, and reports from the builder of the structure. Don't forget a hammer drill, bits, and a penetrometer to determine soil compaction. Think about other issues that might create problems like slabs binding (concrete saw?), bent rebar from a settled slab, etc. Make sure you have considered all the tools you are going to need for the job and the cleanup.

Visualizing the Mobilization

After the data gathering is complete, it's time to visualize the job site as a whole and consider any challenges to mobilizing and physically reaching the areas that need lifting. Think about potential issues: How big is your rig? Is a trailer rig or a box truck rig going to face challenges getting into and out of the area? And once your rig is in place, do you have enough heated hose and pump power to get the required volume of material where it needs to go to do the lift?

Some of the above seem obvious but it's often the obvious things that get overlooked. Mistakes can drastically cut into your profitability and reputation. There's a reason pilots go through the same checklist prior to every flight. Sometimes you only get one chance to do the job.

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Understanding the causes of slab or structural settlement is key for the contractor to help identify potential opportunities for slab jacking with polyurethane.

Though there are many reasons for sunken slabs, we have identified the three main conditions that cause the settling issues we like to fix. These include erosion, poor compaction, and biological decay.

Erosion Often Leads to Concrete Slab Settlement

Erosion is the most common cause of settling and the most common reason for slab jacking. Poor drainage, improperly placed downspouts, leaking drain pipes, and broken water lines are common culprits. Water can either slowly erode soil over time, or very quickly erode away the soil beneath a concrete slab or structure causing it to settle.

Poor Compaction Can Cause Settlement & the Need for Raising Concrete

When backfilling on a jobsite, the site contractor is supposed to walk in backfill (drive over it with heavy equipment) and compact it in small lifts. However, this isn’t always done properly for one reason or another (inexperienced operators or people taking shortcuts). The result can be soil that will continue to compact itself and settle over time.

A great example of this is bridge approach slabs. These slabs are found on roads and highways all over the world. Bridges typically sit at a higher elevation than the roads that approach them. During construction, the final section of road (typically a concrete slab) is built on backfill to raise the elevation to meet the bridge. Over time, the slabs can settle due to poor or improper compaction. Compounding the problem is the fact that when a slab settles a little, the expansion joint opens up and allows water to get underneath the road, adding erosion to your compaction problem.

Biological Decay Can Result in Sinkholes and Sunken Concrete Slabs

Construction trash pits, buried trees, and other biodegradable materials all eventually break down. Sure enough, there always seems to be some corner of a building or a separate parking area or driveway that ends up right over it. These situations can range from slight settling to very severe.

Sometimes you have a combination of factors that cause settling. As we discussed in the bridge approach slab issue, poor compaction can lead to settling which will open a joint and allow water to compound the problem with erosion. Property owners and managers should not ignore these problems, or they will become more expensive to fix over time.

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Slab Jacking vs. Replacing Concrete

So, you're faced with a sunken concrete slab that could be repaired via complete replacement or being lifted back into place. How do you know which option to choose? Here are a few things to think about.

Raising Concrete is More Cost Efficient Than Replacing

If the slab is in good shape, and is of a reasonable enough size and thickness, it is usually going to be more cost effective to lift it back into place with structural polyurethane foam. Our PMC pumps can deliver the AP Lift series of foams as far as 400 feet away through heated hoses. And remember, wherever you deliver new concrete, you have to haul away old concrete.

More Environmentally Friendly with Polyurethane Concrete Lifting

Everybody wants to be green and take care of the environment these days, because it's the right thing to do. There is an environmental impact every time concrete is replaced. The cement manufacturing process is the second largest cause of greenhouse gas emissions in the world. Additionally, there is the issue of what happens to old concrete once it is removed. One would like to think it is recycled, but more often than not it ends up being dumped. Hopefully that would be in a landfill, but we've all seen piles of concrete rubble in places where it would be considered trash or pollution. It's worth considering. Meanwhile Alchemy-Spetec's AP Lift 430 and AP Lift 475 are so environmentally friendly they are NSF approved for contact with drinking water in their cured state.

Polyurethane Slab Jacking Requires Less Downtime

Last but not least, how long can a property owner or manager afford to have that area out of service? Consider a busy warehouse, an airport taxi way, or a bridge approach on a highway. There is an economic impact when those are out of service for replacement. It can be a couple days before new concrete is traffic ready. Wouldn't it be better to have it lifted in a few hours, and then back in service 15 minutes after the slab jacking is done? I know what I would want.

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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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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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In a recent media interview, I was quoted as follows: “Ultimately, the customer is the property owner, somebody who’s got a problem. Even though we’re selling to contractors, we kind of all have to be on the same page.” That view has motivated us to pay close attention to what contractors, engineers AND property owners are most concerned about regarding the use of polyurethane. Over the years, we’ve noticed three main questions that arise over and over again:

1. Are the polymers strong enough?
2. Are they easy to install?
3. How quickly can the job be finished?

So we’re going to take a look at each of these three core issues in detail…

Powerful Polymers

Concrete Leveling Foams

In my blog post Slab Jacking With Polyurethane Foam – How Strong is Strong Enough?, I point out that the National Home Builders Association and the International Building Code list stiff clay as having a 4,000 lbs per square foot load bearing capacity and crystalline bedrock as having 12,000 lbs per square foot capacity. Our lifting foams have load bearing capacities of 7,200 to 14,000 lbs per square foot after curing in a free rise state. 

When Alchemy-Spetec foams cure in a confined state underground, that bearing capacity has been known to be even stronger. Testing data in the lab shows that our lifting foams will increase in compressive strength: In a space confined 25% by volume there will be an increase of 31% in psi and in a space confined by 75% there will be a 79% increase in the psi.

The Alchemy-Spetec lifting foams are used to level airport slabs supporting jumbo jets, heavy equipment, building slabs supporting tremendous loads, and even railway slabs supporting the heaviest freight trains.

Leak Seal Resins

Alchemy-Spetec leak seal resins have been used in many applications, including shutting down a 2-million gallon per day leak at a water treatment plant. The leak was reduced from 1,700 gallons per minute to just 10 gallons per minute (attributed to the many vintage valves and fittings that are still present at the plant). They are also used in other applications such as curtain wall grouting.

Soil Stabilization Resins

Unstable, eroded, or loose soil around infrastructure can result in settlement and damage to the structure. Voids can be filled, seawalls remediated, soil consolidated, and water migration halted by injecting the soil with Alchemy-Spetec soil stabilization resins. In my blog post Soil Stabilization Products Prevent Cave In Beneath Busy Intersection, I profiled a powerful example of AP Fill 700 in action. Inspectors in Orange County, Florida found a depression in the middle of a busy intersection that was due to an underground sewer line that wasn’t sealed. Water and eroding soil were infiltrating the sewer line causing the road to slowly settle. The resulting voids around the drainage structures had the potential to grow larger, eventually resulting in a complete cave-in of the roadway. A point repair was done from within the leaky pipe to stop the infiltration but they feared it was only a matter of time before the road gave way. We devised a solution for their crew to use the versatility of AP Fill 700 as both a permeation and void filling grout.  To keep the lane closure down to a bare minimum of time, the project was successfully completed on two separate Saturdays. The voids were filled, the loose soil was solidified, and only minor asphalt patching was required to make that area smooth for traffic again.

Orange County Utilities Supervisor Paul Morrison has been enthusiastic about AP 700 since the first time he tried it out on a severe manhole leak, when he had this to say…

“Based on our extensive prior experience, we expected to use at least five to ten pails to stop this leak. With Alchemy-Spetec material we were able to do the job with 1/10th of that amount. Their product will save our crews a lot of time and labor, and save the taxpayers of Orange County a lot of money.”

AP Soil 600 is one of the most versatile permeation grouting products on the market. It can be characterized by its single component, moisture activated, hydrophobic, and low viscosity qualities. It can fortify sandy soil to strengths approaching 2,000 psi.

Painless Procedures

As I never fail to point out, application procedures for Alchemy-Spetec products are relatively painless. The installation process is very clean compared to replacing the structure or repairing with cement grout.  Polyurethane is lighter than cement, so it doesn’t sink. Alchemy-Spetec products do not shrink after installation. The closed cell structure makes these resins impermeable. 

Rapid Results

Application of polyurethane is usually less expensive than replacement. Polyurethane concrete repair is also less time consuming. Any structure repaired with Alchemy-Spetec products is usually ready for use 45 minutes after application.

There you have it – the three most critical issues for contractors, engineers and property owners regarding polyurethane concrete repair. By staying focused on these concerns we constantly remind ourselves WHY we do what we do. We do it for YOU.

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As a technical consultant, I often assist customers when they're put to the test with difficult jobs. That's why we go out of our way to provide the powerful polymers and painless procedures they need to achieve the rapid results those projects require. For an in-depth dive into what we mean by powerful, painless and rapid - see this blog post I wrote awhile back. Then watch the video below to see powerful polymers, painless procedures, and rapid results in action... 

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