Alchatek Blog

This post is part of the Alchemy-Spetec Contractor Lens series, featuring views, news & case studies written by our customers.  This article, originally posted on the Dalinghaus Construction Blog, explains the basics of polyurethane concrete leveling.  If you're an Alchemy-Spetec customer and you'd like to discuss writing content for our blog, please send an email to marketing@alchemy-spetec.com today!

Lifting concrete with polyurethane is a process that takes a lot of simple physics into play.  The amount of recovery that you are able to get out of a slab of concrete is dependent on a lot of underlying factors.  Not only does the amount of area that is needing to be recovered play a role, but also the construction of the slab plays a massive role in what can actually be recovered.  Let's dive into how the process actually can lift a sunken slab of concrete.

When you are looking at a sunken piece of concrete you first have to envision of how this slab of concrete will react once you start the lifting process.  Once you do so, you can then figure out where you are going to perform you first injection.  We will then inject polyurethane through a drilled hole until we start to see movement out of the slab.  We continue drilling and injecting until the slab has been set back into place as it was when it was initially poured.

When the polyurethane is first injected through the slab it will typically fill any voids or cavities that are under the slab.  Once these have been filled the polyurethane will start to compact the soil that the slab was resting on.  It will continue to compact the soil until it gets to a point where the soil starts to become solid and the slab begins to lift.  The polyurethane will continue to compact the soil and lift the slab until the slab has been leveled to the desired elevation.  

It is a simple process if you think about it.  It is easier for the polyurethane to lift the concrete and its weight than to push and compact the soil further into the earth.  Although some looser soil requires more polyurethane to be injected, it will still eventually get to the point at which it is easier to lift the slab than to continue to push the soils downward.

Here are the steps simplified:

1. Analyze the area to be lifted
2. Drill a hole through the slab
3. Install a polyurethane gun
4. Begin injecting polyurethane material
5. Monitor slab movement 
6. Stop injection once recovery has been attained
7. Remove gun and port
8. Grout hole

Click here for more information on Dalinghaus Construction.

Want more information on polyurethane concrete leveling?

We understand that chemical grouting is often not the primary focus of a construction or repair job, but a water leak can often bring the rest of the job to a screeching halt until it is sealed. Job costs then start to pile up, production or facility services stay shut down as time drags on, sometimes tempers begin to flare. Sound familiar?

It’s not an exaggeration to state that Alchemy-Spetec has the most experienced and responsive technical support squad in the industry. In the spirit of the famous postal service motto, “Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds”, our approach is somewhat along the lines of, “Neither weekends nor evening hours nor holidays…”. In other words we strive, to the best of our ability, to be there for you when YOU need us.

For example, Alchemy-Spetec has provided technical support for critical infrastructure jobs over Thanksgiving, Christmas and New Year’s Day. While on-site technical service response is based on availability and job circumstances, we have a track record of being there when it counts. In the chemical grouting industry, almost all other manufacturers have moved away from dedicated fulltime support personnel. We stand alone to help you when YOU need it.

Want more information on Alchemy-Spetec products?

I recently provided on-site technical support on a job with Foundation Repair of Western Colorado. A post-tension residential slab had some interior settlement issues. (Post-tension slabs are constructed with embedded high-strength cables that keep them from cracking or moving.) It looked like the settlement was due to an issue with the cables, either a faulty installation or failure to properly stretch them after the install.

Are Post-Tension Slabs Dangerous?

When working on a slab containing post-tension support cables, you must be extremely careful. These cables are typically stressed to greater than 30,000 lbs tension. If you accidentally drill through or cut a tensioned cable, it can likely rip out of the concrete with a sudden whip-like motion. Consequences could include slab destruction, equipment damage, serious injury, or even death. A few years ago, I witnessed a geotechnical engineer accidentally cut a post-tension support cable when drilling through a slab for a soil boring sample. We were inside a building. The cable snapped with a sound like a massive gunshot. It shot out from the exterior of the foundation wall. Fortunately, no one was standing near that area at the time. Nor was there any valuable equipment nearby. However, serious damage was done to the slab.

How to Repair Post-Tension Slabs

While consulting on this job with Foundation Repair of Western Colorado, we used ground penetrating radar to locate the cables before doing any post tension slab drilling. The crew then marked the “no-drill” areas and was able to safely drill through the slab for polyurethane injection. In addition to locating the post-tension cables, we used the GPR system to locate rebar within the slab and check for underground utility lines.

Ground Penetrating Radar uses radar pulses to image the subsurface. It is a non-intrusive method of surveying the sub-surface to locate underground utilities such as electrical conduit, plumbing, duct work, cables or masonry. GPR can also often identify the location of voids under the slab, providing helpful information in the injection process.

This slab lifting job went very well. The crew used AP Lift 430 to level the slab. The settlement was remedied, and the customer was very happy with the results.

Want more information on slab lifting products and procedures?

Contrary to popular opinion, as a contractor, you don’t have to put up your equipment and rigs due to cold weather. There are many jobs to be done and many ways to keep your material conditioned. Use this season to your advantage and gain valuable business.

Cold Weather Markets

Seasonal attractions such as theme parks are a great place to start looking for winter work. Many of these parks (the ones that aren’t in Orlando) shut down for the winter and this is the time they do maintenance and repairs. Think of all the concrete lifting and leveling that can be done.

Factories can be less active in the winter months with production slowing down in many industries. This is a good time for them to do maintenance and floor repairs as well.

Warehouses typically operate year round, so there is always work available. Warehouse floors are used and abused on a daily basis and will sooner or later need some form of repairs done to keep business running at a steady pace. In addition, many warehouses have dangerous voids beneath their floors that require repair.  

Exterior concrete slabs are still worth considering, even in the cold weather. These slabs experience the most wear and tear from the environment itself (think erosion) and daily traffic. You’ll need to lift concrete slabs before the ground freezes and only after your materials have been thoroughly conditioned.

Conditioning Materials

Your slab lifting equipment probably has built in heaters and a heated hose. Each brand and model of pump has different sized pre-heaters and different ∆T (∆ = Delta and T = Temperature). This sounds complicated, but is actually quite simple.  ∆T is simply the change in temperature.  Let’s say your material has been sitting in a cold trailer all night and the temperature has dropped to 40 degrees F. If the required temperature of your B side material is 120 degrees F, then your pump better be rated with a ∆T of at least 80 degrees. However, if your material is preconditioned to 70 degrees F, then your machine only has to be rated for a ∆T of 50 degrees. As I said, every machine is rated differently based on the size of the heaters. What is important to know is that there are limitations to how much heating your machine can do.

Keeping your materials conditioned in the winter months is a lot easier than it sounds. The main point is to keep your AP Lift products above 60 degrees at all times. Keeping the polyurethane at or above that temperature can be accomplished in a number of ways.

If you have an insulated rig, it should stay around 40 degrees warmer than outside temperatures. Most foam rigs have built in electric heaters that require an extension cord to a power outlet at the job site or at your facility for overnight storage. Alternately, you could buy an electric radiator heater. Other available heating devices include drum band heaters and heated drum mats (be careful not to scorch the polymers by turning band heaters up too high). For a more DIY approach, you could build a hot box around the material storage area in your rig.

Heat Sink

Another consideration when lifting cold slabs is the heat sink factor. AP Lift products come out of the gun hot and get even hotter as they react. However, cold concrete acts as a heat sink and sucks the energy out of the foam as it starts to react. This can slow down the reaction speed of the foam. If you are pumping into a void, it will have little effect because most of the foam is not in contact with the concrete. If you are trying to lift a slab with little void, it will have more of an effect because more of the foam is in contact with the cold concrete and cold soil. More volume = more energy.

Conclusion

Don’t let common preconceptions deter you from slab lifting in cold weather. As noted above, there is no need to shut down completely for the upcoming winter months if you don’t want to. Opportunities still exist and one of them may just be the job you’ve been looking for all year. There are many ways to keep your equipment and materials conditioned to efficiently work in lower temperatures. Have more questions about slab lifting in cold weather? Call us at 404-618-0438.

Editor's Note: This post was originally published in 2018 as Slab Lifting in Cold Weather.

Want more in-depth info on slab lifting?

I don’t know what it is about this time of year but for some reason at the beginning of fall we receive the most tech support phone calls from slab lifting contractors. Some of it is related to the changing weather, but this past week several things happened that made me want to address a specific topic – the compressed air system of the polyurethane foam rig.

It’s easy when discussing a trailer or box truck rig setup to focus on what type of plural component machine you are running. We all want to know whether you have a PH-2 or an E30 for example, or maybe an air powered Boss proportioner. What is often overlooked and neglected is the compressed air system in the rig. For a slab lifting contractor, it’s likely your air system is working harder than any other component on your rig. If you have had the joy of standing next to the compressor while it is running, you can’t deny that.
I want to highlight the main components of the compressed air system; describing their purpose and offering a few tips for keeping them running like they’re supposed to.

These components include:

• Air Compressor
• Coalescing Filter and Moisture Separator
• Refrigerated Air Dryer

Air Compressor

The majority of slab lifting rigs we see have reciprocating air compressors, also known as piston air compressors. These are identified by having a tank, and they are in a horizontal or upright configuration. They can be either gasoline or electric powered. There are also rotary screw compressors out there which don’t have a tank but still need to be maintained. If you have a compressor with a tank, that tank needs to be drained of the moisture it collects. Some have automatic drains that pop open after the unit shuts down; others must be drained manually.

Last week we worked with a contractor who had an air powered proportioner. His machine could build up pressure, but once he started injecting poly the flow would slow down to just a trickle. He would then shut off the gun and the proportioner would pressure up again. Turns out the air compressor tank was almost completely full of water so he would exhaust the remaining air supply right away when shooting the foam. A good policy is to drain the tank every day at the end of the shift. If it doesn’t drain automatically then there are typically valves that are easy to access. I actually like to start my compressor up the next shift with the tank valve open because it will always blow some more water out when it fires up. Then I shut the valves and things pressure up per usual.

In addition to draining the tank, you need to check and change the compressor oil per the manufacturer’s guidelines. This is for all compressors. If you don’t have a manual on board the rig to tell you when to change the oil or what oil to put in, this info can easily be found on the internet or hopefully from your rig provider.

Filters and Moisture Separators

You can usually find the moisture filter and separator mounted on the wall, often combined with the regulator and air pressure gauge. These filters have a housing below them that collects moisture that is coming from the air compressor. This is the first line of defense (after the air compressor) from keeping moisture out of your transfer pumps, so make sure to open the little valves at the bottom and drain these filter/separators daily. I do it at the end of the day and once again at the beginning of the shift when I am checking my air pressure upon startup.

Refrigerated Air Dryers

The refrigerated air dryer is the last line of defense before the compressed air is sent over to the transfer pumps. I have seen these mounted in various places in a rig from on the floor to up on the wall. First, do not pile tools and other rig items on top of and around the air dryer. These units work nonstop, and they need airflow to do their job without overheating. Take care not to block them in. Second, I believe most of these air dryers also have filters and coils that need to be cleaned occasionally. Check the manufacturers guidelines for your model and keep those items clean so that your unit can run more efficiently and for a longer life.

Conclusion

Your compressed air system is vital to your plural component machine running on ratio and making good polyurethane foam. Components that remove moisture from the air are critical for keeping your transfer pumps running like they are supposed to without breaking down or losing pressure.

Always keep these critical points in mind:

• Drain the tank
• Change the oil
• Drain the filter/separator units
• Don’t block in your refrigerated air dryer, and keep the unit clean

These essential maintenance tasks don’t take but a few minutes, and they can save you hours of frustration and head scratching.

Want more information on Geotech material and equipment?

The choice of a polyurethane material provider for your geotechnical contracting business is a critical decision with far-reaching consequences. In addition to top quality concrete and soil repair material, a premier provider will offer reliable high-performance equipment, rock-solid tech support, extensive training resources and even marketing assistance.

Polyurethane Materials

All polyurethane materials are not created equally. Make sure you ask around the industry to see which materials are the most reliable.

Characteristics of High-Quality Materials

• 100% virgin (do not contain recycled polyurethane).
• Easy on your reactor (does not create high-pressure that wears out your equipment).
• Unlikely to catch fire (yes, some sub-par materials out there will char or catch fire while setting up).
• Capable of bonding to concrete.
• Strong and durable after they set up.
• Approved for contact with potable (drinking) water after curing.

Rigs and Equipment

The quality of your geotech rig is not something you want to compromise on. A premier provider will offer state of the art rigs set ups, customized to fit your exact needs. You’ll want multiple door options (side door, choice of barn door vs ramp door), multiple power outlets and slide-out equipment options. These features allow for maximum flexibility in all types of job situations. In addition, a well-insulated rig allows for operation in a wide variety of climates.

Your pumps, air compressors and slab lifting guns need to be reliable as well.

Characteristics of High-Quality Equipment

• Easy to use (not overly complicated).
• Easy to maintain (easy to clean, not a lot of complicated parts to replace all the time).
• Reliable, reputable brands.

Tech Support and Training Resources

A major differentiator separating serious material manufacturers from the rest is the availability of on-the-job technical support and service. A premier provider will offer field service to assist customers on challenging jobs. Phone support should readily available as well, with support techs ready to answer questions when you need the answers. You will also want to look for comprehensive training resources on material installation, equipment use and maintenance, and estimating/billing jobs. A good combination of online videos and articles, training literature and live events is the sign of a manufacturer dedicated to educating their customers.

Marketing Assistance

Look for a provider offering robust marketing assistance. Geotech contractors have many marketing needs, including website content (illustrations, photos, descriptive text), videos, vehicle sign design, advice on lead capture, etc. A manufacturer willing to go the extra mile in this department can help give you an edge of the competition in your market.

Do Your Own Research, Make Your Own Choices

Did we just describe Alchemy-Spetec in the paragraphs above? Of course we did. This is the Alchemy-Spetec blog after all. That being said, we encourage you to do your own research and contemplate your own needs in a material provider. Ask around in the industry. Seek out users of different brands and find out all you can about their experiences. If you think we missed anything in this article, let us know. We’d be happy to hear from you.

Want more info on Alchemy-Spetec products?

As a consultant on many deep soil geotech jobs over the years, I have found myself recommending one critical piece of equipment repeatedly: The Dynamic Cone Penetrometer (aka the DCP). I highly recommend this tool as an essential part of your Deep Lift® rig set up. As Jim Spiegel explained in his blog post on this subject, this device is used to measure the strength of subgrade soils, and can be utilized to identify weak layers of soil within a soil mass. As you can see in the video below, a hydraulic pump drops a 30kg (60lb) hammer, driving the measuring rod into the ground.

To measure soil strength, the operator counts the number of blows it takes to drive the steel rod in 10-centimeter increments. Good soil requires 10+ blows to drive the rod 10 centimeters. Anything less is typically indicative of weak soil conditions.

DCP testing is a widely accepted means of in situ testing. Due to the common acceptance of DCP testing, many municipalities and agencies are willing to pay for this service.

Here is a hypothetical scenario for DCP use:

Soil strength data is needed under a concrete parking lot before a Deep Lift® job. Multiple tests would be performed, spread out evenly over the area. For thorough testing, each DCP test would be executed to a minimum depth of 15 – 20 feet or refusal (when the hammer blows no longer cause movement.) The test results can then be compared and analyzed to find where potential weak soil conditions may be present. This allows for accurate and effective application of the polymer to address the weak layers.

DCP testing can also be utilized prior to bidding any Deep Lift® job to develop effective injection plans, as well as accurately estimate material usage on projects. With that said, it’s not always possible or practical to perform pre-bid testing. When pre-bid testing is not performed, it would still prove highly beneficial to perform DCP testing prior to injection. I have personally encountered many situations where injection plans have been drastically altered after test results were analyzed (injection depth was added or subtracted, the weakest layers were identified, etc.) The Dynamic Cone Penetrometer is a portable tool which can easily be used in many locations where other testing methods are not feasible and it provides valuable insight into the soil conditions that need to be improved.

Want more information on Geotech products?

When two adjacent slabs are touching, there is a high likelihood of them being bound. This is definitely something to look out for on slab lifting jobs for a variety of reasons.

Bound Slab Basics

If you try to lift a slab that is bound to an adjacent slab, you could end up:

• Lifting a part of the slab that you did not intend to lift.
• Cracking the slab.
• Lifting the adjacent slab unintentionally.
• Wasting valuable extra material trying to lift a slab that is stuck.

Even if a seam between two slabs or a control joint (a joint meant to break when the slab is under pressure in order to prevent cracking) is already loose - it's still best to run a saw through it just to be sure before attempting to lift. A concrete saw blade is 1/8-inch wide. When you cut between slabs, you are giving them a 1/8-inch gap to ensure smooth movement.

Pros and Cons of Two Types of Concrete Saws

There are two types of concrete saws to choose from when stocking your arsenal of slab lifting gear. Here are the pros and cons of each…

Circular Saw

Photo Courtesy of STIHL.

PROS

• Fast cutting rate.
• Low operating cost.
• Easily sourced blades.

CONS

• Requires overcuts (the blade typically extends 4 to 6 inches past the edge of the slab).
• Requires a wide berth. Cannot cut up against edges of walls and structures.

Concrete Chainsaw

Photo Courtesy of STIHL.

PROS

• Doesn't require overcuts.
• Can cut up against the edges of walls and structures.
• Can cut up to 12 inches deep.

CONS

• Has a high operating cost (chains and bars tend to be expensive).
• Low cut footage per bar and chain compared to circular saw blade.

Want more information on slab lifting products and procedures?

This article is an excerpt from Episode 8 of Alchemy-Spetec's podcast The Injection Connection, featuring Matt Chittick and Travis Germick, co-owners of Lift It Rite, LLC, a residential slab-lifting business. The Injection Connection is hosted by Jim Spiegel: Vice President of Alchemy-Spetec and Board Member at the International Concrete Repair Institute. (If you'd rather watch the video clip of this exchange, it is posted at the bottom of the article.)

Jim Spiegel: When you’re on slab lifting job, what do you think holds you up the most often?

Matt Chittick: I would say binding slabs are the hardest thing that we deal with. But we've done a couple of jobs here recently where the bind was good and it allowed something to come up together like we needed it to, versus breaking that crack that was binding apart and lifting one side versus the other side. But binding slabs are generally the hardest thing to figure out and make work for you, I would say.

Jim: So, when you have something binding, when do you make the decision to cut into it?

Travis Germick: Well, you can look at it and say, okay, there's a possibility of it binding or something like that, we'll go ahead and take care of it. I mean, those saw blades we were talking about earlier in the podcast are amazing that we picked up. So we’re not as scared to pull it out and saw through what we got to saw through.

Matt: They cut like butter. That was an actual company that we met out there at the World of Concrete. We bought three blades from the guy. Well, actually he sent us one first. We tried it, we were like, yeah, need more of these. And I don't think we've used any of the ones we just bought. I think we're still on the first one.

Travis: We are. I mean, they're really good blades.

Jim: You want to give them a plug? What kind of blade is it?

Matt: Diamond Blade Warehouse.

Travis: There you go.

Jim: Super blade from a Diamond Blade Warehouse and of all the blades you've used, you think that's one of the better ones?

Travis: Yeah it really is, whether it's a cured concrete, old stuff where the house has been there for forty years or whether it's stuff that’s two years old.

Watch the excerpt...

Want more information on polyurethane slab lifting?

This article is an excerpt from Episode 8 of Alchemy-Spetec's podcast The Injection Connection, featuring Matt Chittick and Travis Germick, co-owners of Lift It Rite, LLC, a residential slab-lifting business. The Injection Connection is hosted by Jim Spiegel: Vice President of Alchemy-Spetec and Board Member at the International Concrete Repair Institute. (If you'd rather watch the video clip of this exchange, it is posted at the bottom of the article.)

Jim Spiegel: If there's one thing that you guys, a piece of advice or some sage wisdom, as I know you guys are full of that as well as punch lines (laughter), what would you say to someone thinking about getting into the lifting business?

Travis Germick: If you're going to get into the industry, I would say get with Alchemy-Spetec and get some training. Hang out with those guys, come down and watch someone do the work. Get with a reputable company, come with us and work for a day or two and see what it's all about.

There's a lot of people that can definitely do this job but there's also a lot of people that could not do this job. There's a work ethic that goes with it. And I think with any spray foam or something like that, if it's insulation or whatever it is but there's a special ethic that has to go with it and special type of person it takes to get into this. But we absolutely love it. Every day, we get up, we're excited to do what we do because our customers’ minds are blown every time they see foam lifting concrete. And we feed off of that. I mean, they're over there like, “wow, that was cool” and I'm like, “I know, right?” That was really neat. We’re really psyched about it as well. There's a lot of times where Matt and I are high fiving each other because, that was a really cool job we just did.

That’s the only takeaway I have with it. I think it's a great industry to be in. I think it's a great service that we're offering and it's cool, too. It really is some neat stuff. What do you think, Matt?

Matt Chittick: I 100% agree. I would tell somebody you can learn all the ins and outs of it but until you get on the job sites and you see some things happen and you kind of roll with the punches, me and Travis, we have fun. If you have fun, it doesn't feel like you're working. And I would say have fun. You want to look for more good jobs than bad, but don't let the bad jobs bring down your attitude because your customers will feed off of your attitude. If you have a great positive attitude, those customers are going to have a great positive attitude. And if they have a great positive attitude, guess what, they love writing checks.

Jim: Yeah. I couldn't agree with you more that the attitude is such a big part of it. And then that starts when you get out of your truck, right?

Travis: Absolutely.

Jim: If you get out of your truck and you’re all smiles and having a good time with them, it just leads into a good experience. Not only do they feel like they trust you, but when things go wrong, they're more tolerant, I feel.

Matt: Yeah, absolutely. I would say because of our attitudes and things like that, we've been able to explain some things to customers and show them what happened here, what happened there and whatnot and they know that we're professional because that's the way we come across. We keep them involved in it, and when they see these things happen, I think they are a lot more tolerant and really accept some of the imperfections. That might be because getting concrete back to the original exact part or area whre it was might not always be what you can do. But if you talk about those expectations and you keep the customer informed and you're upbeat and positive, that's just going to transcend right to your customer and then everybody's okay and everybody's having a good day.

Watch the excerpt...

Want more information on polyurethane slab lifting?