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This article is an excerpt from Episode 9 of Alchemy-Spetec's podcast The Injection Connection, featuring Charlie Lerman "The Grout Geek". Charlie is Director of Technical Services - Leak Seal® Division at Alchemy-Spetec. 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 listen, an audio version of this excerpt is posted at the bottom of the article.)

Jim Spiegel: I always say to people is you should account for some exploration time. Everybody wants to go quick into, "What are the coverage rates, how many linear feet can I do in a day, how many people do I need, what’s the size of the crew, how many man hours as a prevailing wage." But I like to tell people let’s put half a day, even up to a full day depending on the job, into exploration. Would you agree with that?

Charlie Lerman: 100%. Exploratory grouting is the way to go. And on smaller jobs a lot of times, that’s going to knock out the whole job anyway. But when you get to those larger jobs for curtain grouting and crack injection, just having that day to look at and say, “These are the parameters. We think we’re going to be between this and this mark and by this procedure.” You go out there and you find - well, did I fall in that, where did I fall in that and if so, how are we going to adjust out the rest of the job now that we know some specifics there? But until you get out there, it’s really all theory. I’m in tons of meetings where there’s all this theory crafting and people talk about this stuff. And while this theory crafting is great and we need to do it to wrap our heads around the situation, it comes down to it when you’re actually injecting, you don’t have precise control over your liquid, you don’t know exactly where it went. You can only see the result and make assumptions. Whatever I pictured in my mind is what I can say happened in there, but until we rip that open, which almost never happens, you don’t know exactly how it went inside. So again, all that theory and stuff, that’s all great to talk about. But until you put the wheels on the road and see what happens, you just don’t know. I’ve seen stuff where you just start scratching your head - how could this be going that way? But it does and you figure it out and work through it.

Listen to the audio version of this excerpt...

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Single-Component Geotech Pump Skid

The PolyShark is a custom pump skid system for installation of single-component polyurethane geotech resins. This world-class skid set up is essential for large scale seawall repair, soil stabilization, and void fill projects.

The PolyShark includes a gas-powered high-pressure injection pump, two hose reels, and flow meters.

Gas-Powered High-Pressure Injection Pump

A step up for projects that require greater power and output, this custom modified pump is our best-selling gas over hydraulic piston machine, favored by contractors who want to complete large application jobs in record time with high profit margins. The hydraulic ram fluid section is moved front and center in the configuration for easier maintenance and control.

High-Pressure Hose Reels with Stainless Steel Ball Bearings

High-pressure design guarantees durability when used with the high-pressure single-component pump. The construction is completely corrosion resistant and the stainless steel ball bearings, hardware, and manifolds are stronger than the aluminum parts on standard hose reels. The ball bearing-driven hose reels operate smoothly because they contain no bushings. (Bushings easily wear out.)

Flow Meters

Two high-pressure flow meters are capable of recording the exact amount of product pushed through the hoselines. This allows for precision material-use tracking.

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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.

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This article is an excerpt from Episode 9 of Alchemy-Spetec's podcast The Injection Connection, featuring Charlie Lerman "The Grout Geek". Charlie is Director of Technical Services - Leak Seal® Division at Alchemy-Spetec. 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 listen, an audio version of this excerpt is posted at the bottom of the article.)

Jim Spiegel: What’s some of your favorite equipment to work with? Favorite pumping systems?

Charlie Lerman: I’ve always been a fan of the airless paint sprayers (a.k.a. modified electric injection pumps). They’re just a good workhorse and have been the industry standard. So I like those and that’s what I used most of my career. I’m dealing a lot more now with acrylate type products. And I do really like the pumps that we use for those, the plural component stainless steel pumps. Finally, I’ve seen some that are not difficult to use, which is nice to find one that’s easy. It’s still a complex machine but it’s broken down and very easy. I’d say that’s one of them that’s coming up right now. But still, it’s hard to just go away from that old reliable Graco or a Titan 440.

Jim: Yeah, for sure. It’s pretty much the status quo out there.

Charlie: But Jim, let me add - to jump on the other side of that, and we offer these pumps, it’s not like I’m badmouthing a competitor or something like that but there’s the drill pumps. And while they have their place these little drill pumps, I believe that they actually are hard for contractors because a lot of the people that look at getting the drill pumps are first-time grout users and they’re trying to save some money. So they’re getting a drill pump rather than an airless paint sprayer to save a couple hundred dollars there. The problem is that using that drill pump takes a little more technical expertise. So if it’s your first job, that’s not always the good pump to cut your teeth on. It’s got it’s good position and stuff like that and it’s light and it’s easy to move around but it does take a little more skill. That’s one of the pumps just kind of to watch out for.

Jim: Yeah, as you and I have been pretty open about, not everybody has the same experience with different equipment. You’ve pumped a lot more grout than probably all of us, but I have quite a bit of experience with the drill pumps. I agree with you. Probably the benefit that I see is that they’re easy to take apart. So, when there are issues with it, which can happen to any pump that you’re pumping chemical grouts with, you’re looking at seven Allen screws and you’re into the ball and spring assembly - so you’re pretty much in the guts of it with seven screws. That’s the only thing that I really like about it just from a maintenance standpoint. I agree completely that if you’re doing this a lot, you’re probably not doing yourself justice with it. Especially if you’re getting into higher volume sort of stuff. I mean, for any curtain or soil grouting it’s just not relevant. And you’re mixing a lot. You’re mixing small volumes all the time. As you know from being on site, especially on large volume applications, keeping product mixed can be a huge functional manpower issue. Because you just don’t account for all the time needed for having that guy keeping things mixed. I see the pros and cons for it. But it’s well noted that you’re not a huge fan.

Charlie: No and it’s still a great product. There is a niche for it though. And really that’s my main concern. And I think also that comes from my history because often times I’m either on giant projects and that’s where they’re demanding to have that customer service out there. And they’re not even looking at these pumps because, like you said, they’re just not high volume. And then the other times where I’m training people is a lot of times when they’re brand new. And it’s just not a great pump for someone brand new. But it’s light, it’s easy to maneuver and that is an advantage a lot of times when you’re just setting up and if you’re doing a residential area or you’re doing something small or you’re doing something that’s off the beaten path and you don’t want to have to carry a whole bunch of equipment.

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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.

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I often get asked about pre-drilling for crack injection. Pre-drilling is the practice of putting all the ports in position before injecting anything. This preparation procedure can often be very time efficient. Think of this an assembly line approach. Pre-drilling is often done when there is “shut-down” period on a job with a limited time to get the work done. You’ll encounter these types of jobs in subway systems, for example, when the work needs to be done while the trains aren’t running. That’s just one specific example, but you get the idea.

Drilling and injecting one hole at a time, on the other hand, allows you to follow the path of the water as you start to seal the leak. Here is how I described the process in my blog post Port Spacing and Location, “I start from the bottom, work my port, and then observe how far the grout travels. I then place next port to pick up where the grout left off.” With the drilling as you go approach, you usually end up with less holes and a more complete seal.

To pre-drill or not to pre-drill? That is the question. As you can see, the answer depends on the circumstances.

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Port spacing in the case of crack injection has nothing to do with the distance between a port in Miami and a port in Jamaica. In this case, we are simply discussing how far apart to place your injection ports. This is not a fixed distance, as proper port spacing varies depending on site conditions.

For estimating, 1’ on center is the standard and will cover you pretty well with the exception of hairline cracks. Typically, the tighter the cracks the closer the spacing.

I am not a big fan of predrilling the ports as you never know when you are going to hit that sweet spot and get 3’-6’ of travel. Or on the other hand when you have numerous dead holes or very little grout travel. So I start from the bottom, work my port, and then observe how far the grout travels. I then place next port to pick up where the grout left off.

I see predrilling done on shutdown jobs where time is of the essence. This may lead to some extra holes and wasted ports but can speed up the injection process. If it is not shutdown work, I prefer to be more methodical and drill as I go.

Lastly, whenever possible, stitch grout. This is the practice of alternating the sides of the crack to install your port. This helps prevent cracking and spalling of the concrete.

Crack injection is a thoughtful and methodical practice which is not for the impatient.

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This article is an excerpt from Episode 9 of Alchemy-Spetec's podcast The Injection Connection, featuring Charlie Lerman "The Grout Geek". Charlie is Director of Technical Services - Leak Seal® Division at Alchemy-Spetec. 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 listen, an audio version of this excerpt is posted at the bottom of the article.)

Jim Spiegel: One of the questions that I really want to start incorporating into a lot of these episodes is, "Who have you learned the most from in the industry? We’ll take a little opportunity to name drop a couple of people but who have been some of your beacons in the industry who have taught you what you’ve learned?

Charlie Lerman: There are two main names that come up real quick. First there is John Ziebell. I worked directly with him for the six years that I was at De Neef and he was quite the resource for me. And then Scott Anderson also taught me a good amount and just really helped me out. And really the only reason I probably didn’t get more from Scott Anderson is just that I lived in Houston and he lives up in the New England area. Those are the two main people. I really think that they gave me my foundation to build from. But where I learned the really cool minutiae stuff is from all the intelligent engineers and contractors that I deal with. Because again, when we sit down at the table and we try to design a job, it’s not just one person. I mean, when I got in this industry, I’d never worked on a dam before. But I’d done crack injection. I understood that. So when I went to my first dam project, I had a lot to learn about that structure per se but we had the engineer and the owners. They knew the dam. I knew my product. And then we had us coming together. So I’m in a unique position where I get to pick up all this little nuanced stuff. So when you look at someone who’s out there doing crack injection or doing chemical grouting every day, they’ve got a good routine and they know their stuff for that - but they’re typically looking at similar types of projects. Whereas I get to see anything from a dam to a manhole. I’ve actually consulted on a job where we drilled into a window and grouted between CMU block and glass. That is the kind of unique stuff that just comes from those kinds of travels.

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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.

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As we stated in a previous blog post, Lifting Slabs in Cold Weather, there are plenty of jobs that need to be done in the winter. This is just as true for sealing leaks as it is for slab lifting. So let's take a look at those cold weather leak seal markets. We'll also review some special considerations for conditioning leak seal material and equipment. Then we’ll leave you with a few cold temperature leak seal application tips.

Cold Weather Markets

You have a variety of options for seeking jobs that are inside, out of the elements, during the winter months.  Hopefully these ideas will spark more brainstorming on your part. First up we have tunnels, both pedestrian and vehicle. Tunnels often leak, sometimes significantly enough to result in quite a big job. Aquariums are another possibility. As you can imagine, there are infinite potential leak problems in a structure holding that much water. Other possible large jobs could include mines and water treatment plants (which have plenty of interior spaces with potential leak issues). On the smaller side, there are utility vaults, lift stations, manholes and elevator pits.

If you’re still up for working outside during the winter months, you’re in luck because concrete contracts during colder weather. The contraction makes cracks open wider. Wider cracks make leaks more apparent to the property owner and make them easier to repair.

Conditioning Materials and Equipment

One important point to understand is that cold weather requires you to make an extra effort to keep your materials and equipment warm. Cold material reacts slower and gets thicker. Be sure to store your materials and equipment in a heated room the night before the job. When on the jobsite, there are many ways to keep everything warm. Use an enclosed vehicle, like a box truck, enclosed trailer or pickup truck with a camper top or bed cover. Keep as much material and equipment inside the vehicle as possible when working. Use a portable heater to maintain a warm temperature. You can also use electric pail heaters to keep your resin ready for action.

Remember that it won’t do you any good to heat the resin if you’re pumping it through cold equipment. The cold steel inside the pump and the cold hose will literally suck the heat out of the resin before it gets where it needs to be. This will increase the viscosity, making it harder to mix with the water and it will slow down the reaction dramatically. So don’t neglect the equipment side of the equation!

Cold Temperature Application Tips

If you’re using a product with an accelerator, you may need to use a faster accelerator or increase your percentage. Also, bring lots of oakum. You may have to use more if the cold temperature slows down the material or the contracted concrete has made the cracks wider.

If your job requires you to inject into a structure underwater (and the water’s cold), you can use a technique called twin streaming. In this approach, you hook two valves together in parallel fashion – then inject warm water along with the resin to kick start it reacting before hitting the cold water.

Conclusion

I hope this overview has helped spark some ideas on your part for finding leak seal work during the winter months. Just remember to keep your materials and equipment conditioned and you should be fine. Have more questions about polyurethane leak seal in cold weather? Call us at 404-618-0438.

Editor's Note: This post was originally published in 2019 as Polyurethane Leak Seal in Cold Weather.

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