Municipalities across North America have widespread problems with Inflow and infiltration (I&I). Inflow is in reference to stormwater that invades sewer systems. Infiltration is in reference to groundwater infiltrating manholes, lift stations, pipes, and other sanitary system components. While there are a few solutions on the market for mitigating inflow, this article is primarily focused on mitigating infiltration with polyurethane grout.

What are Sanitary Sewer Overflows (SSOs)?

According to EPA.gov, sanitary sewer overflows (SSOs) can be found all over the country and pose many dangers to public health. They estimate there are at least 23,000 - 75,000 SSOs per year in the United States alone. Because SSOs contain raw sewage they carry bacteria, viruses, protozoa (parasitic organisms), helminths (intestinal worms), and inhaled molds and fungi. Because of this, they may cause diseases ranging in severity from mild gastroenteritis (causing stomach cramps and diarrhea) to life-threatening ailments such as cholera, dysentery, infections hepatitis, and severe gastroenteritis.

Massive Amount of Funds in Place for Sewer & Stormwater Infrastructure Repair

Thankfully, hundreds of billions of dollars are budgeted for addressing these issues according to EPA.gov. The CWSRF (Clean Water State Revolving Fund) was created by the 1987 amendments to the Clean Water Act (CWA) as a financial assistance program for a wide range of water infrastructure projects. This program is a key relationship between the EPA and states that replaced EPA's Construction Grants program. States now have the ability to fund a range of projects that address their urgent water quality issues.

A Simple Plan for Mitigating Sanitary/Stormwater System Infiltration

The grouting plan shown below provides the highest return on investment:

1. Inspect lift stations and manholes.
2. Identify obvious and large leaks.
3. Point repair with polyurethane grout.

Typically, a two-person crew can quickly mitigate 10-30 gallons per hour in less than a day. Just this one day’s work will usually equate to $30,000 a year in savings depending on local treatment costs. For more information on mitigating infiltration with polyurethane grouts, call the Alchemy-Spetec technical support team at 404-618-0438 today.

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One of the most common questions I get about leak seal grout is along the lines of "Can I do this or that? Will it work?". I get this type of question regularly because every job is very unique and there is no one precise grouting procedure that fits everything. Let me introduce you to a term I love to use: exploratory grouting. This is the phase in which you are trying various methods until you find one that works for your particular application. While this just sounds like guesswork, it is very far from that.

So, I have come up with a short three-item list of the things you should not do while chemical grouting with urethanes:

1. Do not eat the grout!
2. Do not get the grout in your eyes!
3. Do not add water to the grout before pumping it. (Actually, there are rare times you do this.)

If you do not break those three rules, your work falls under exploratory grouting. We have a standardized leak seal crack injection procedure that will maximize your result (in a laboratory setting). But concrete restoration does not happen in a laboratory. Start with the procedure, but understand that the procedure is written for the spirit of what we are trying to accomplish. It is not written in stone (as long as you're following the three rules I have listed above).

Pro tip: Number one, do not eat the grout, seems like a no-brainer but it exists because we had a call from someone saying, "My worker ate your grout". 

In summation, remedial waterproofing is often an explorative process and can require on-the-fly adjustments. Setting expectations, maintaining open communication with all involved parties, and attention to detail are essential to making the waterproofing process efficient and successful. Here at Alchemy-Spetec, we have a wealth of experience navigating all types of waterproofing projects. We look forward to assisting you with your specific needs.

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Do you know that leak that returns every year no matter how much hydraulic cement you put on it? Why not make this next time the last time you have to mess with it? Polyurethane grouts have some unique properties that allow them to do things concrete cannot. One of the most glaring is its flexibility.

I like to ask the question, "What is the difference between a joint and a crack?" A joint was engineered by humans while mother nature adds her cracks where the engineer did not see the need for one. They allow the concrete the ability to flex a bit as needed. These cracks can be caused by temperature changes, loading, and unloading, or even a difference in the coefficient of expansion of dissimilar materials, like a metal pipe in a concrete wall.

So, as you pick up that bucket of hydraulic cement, ask yourself, "Is this a dynamic leak? Is movement the issue at hand?" More often than not, movement is the issue and the solution is a flexible polyurethane grout. Spetec PUR GT500 and Spetec PUR F400 are two of the main Alchemy-Spetec grouts used in parking garages, elevator pits, and such. Spetec PUR GT380 is the main grout when it comes to sewers, wet wells, and the like. All of these grouts are highly flexible, NSF 61 certified for contact with drinking water, and allow the concrete to move without allowing it to leak.

Another misconception is that a repair material needs to be dry to effectively waterproof a structure. With polyurethanes that is completely wrong. We want and require water present when injecting the urethane grouts.

So, in summary, the best practice is to quit using hydraulic cement in situations where it will fail because of movement. Instead, waterproof once and effectively with a flexible polyurethane grout and be done with it.

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Polyurethane foam was first discovered in 1937 by Dr. Otto Bayer who lived in Leverkusen, Germany. Bayer was a German chemist and was the head of the research group that discovered this new material. His fundamental idea of combining small volumes of chemical substances together to react into a dry foam material was viewed to be an impossibility. But after many trials and difficulties, Bayer eventually succeeded in synthesizing the first polyurethane foam.

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. By the 1960s, polyurethane began being used for grouting purposes as we know it today. Here’s a brief snapshot of the history of polyurethane grouting:

• The 3M Company in the United States and Takanaka in Japan both introduced polyurethane grouts in the 1960s.
• 3M’s product was called Elastomeric 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.

Alchemy-Spetec CEO Stephen C. Barton started his career pumping 3M 5600 to seal cracks in the Atlanta subway system back in 1985. He was amazed at what it could do back then, and we're all still amazed at what our products do today. Despite still being specified in outdated documents, 3M exited the business many years ago and no longer manufactures the grout. In the last few decades, polyurethane grouting has become a widely accepted method for sealing leaks, stabilizing soil, and lifting slabs.

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Charlie Lerman, a.k.a. "The Grout Geek", is Alchemy-Spetec's Director of Technical Services - Leak Seal Division. The importance of waterproofing became critical to him while serving on nuclear submarines in the U.S. Navy. With decades of experience in construction and leak seal, Charlie commands unparalleled expertise in grouting techniques and water mitigation.

The vast majority of grouting done in mines is cementitious. Only a fraction of it is done with chemical grouts. This is not because of the effectiveness of chemical grout but rather due to their higher cost. Chemical grouts have a long and successful history of use in mines.

Today I want to focus on a fraction of a fraction when grouting in mines: polyurethane chemical grouts. Or as I like to say, the grout for when all else fails.

So let us start with which urethanes are the go-to. The hydrophobic polyurethanes, both one and two-part, typically have better chemical resistance than the hydrophilic polyurethanes, thus they are preferred in mining applications. More often than not a rigid or semirigid grouts are selected as they have a high expansion factor to help minimize costs. Also, mines typically don't need to be 100% water-tight. Rigid polyurethane grouts in a crack or fissure may leak a bit after that crack moves but their ability to fill voids and stop high flows of even cold water make them more popular than their flexible counterparts.

Polyurethanes are normally used in high flow situations, used to shut off flows so cementitious grouting can continue, and in high salinity environments where sodium silicates cannot be used. They are field adjustable and have superior characteristics to most other types of grout, except when it comes to cost. The majority of polyurethanes are NSF-61 approved for contact with potable water, contain no VOCs, are inert when they cure, and only produce carbon dioxide while curing. Lastly, the leak seal pumping equipment is extremely low cost when compared to other mining and grouting equipment. The one Achilles heel of polyurethanes is their temperature resistance. They don't perform well over 165 F and are not fire-resistant, which precludes them in some applications.

In summation, when you need a hail mary for water control in mining, polyurethane chemical grouts come to the rescue at a premium - and they're worth it!

Want more information on Alchemy-Spetec leak seal solutions?

Charlie Lerman, a.k.a. "The Grout Geek", is Alchemy-Spetec's Director of Technical Services - Leak Seal Division. The importance of waterproofing became critical to him while serving on nuclear submarines in the U.S. Navy. With decades of experience in construction and leak seal, Charlie commands unparalleled expertise in grouting techniques and water mitigation.

Cracks in Concrete Left Unchecked

Although it’s not unusual to find cracks in concrete, they could lead to detrimental structural issues in the future if not taken care of immediately. But why do concrete structures seem to crack so easily? This issue often occurs due to movement caused by thermal conditions and expansive soils.

And over time, you’ll typically see that these concrete cracks can widen and result in water infiltration, and corrosion of the reinforcing steel. The worst-case scenario we want to avoid is the structural integrity becoming compromised. These cracks are not only a bad look, but they can seriously threaten the lifespan of the structure if left unchecked.

A Quick Look at Polyurethanes vs. Epoxies

This naturally leads us to the next important question to answer: how can we fix it? As usual, there are a few methods used to tackle this problem. In this post, we will cover two popular but different methods: polyurethanes vs epoxies. The reality is that both products can work to address cracks in concrete but under very different conditions.

Due to high compressive strengths, Epoxy is used for cracks in need of structural repair. Often, epoxies even have higher strength ratings than the concrete being repaired. This is why they are the best choice for structural cracks.

Nonstructural cracks that are not leaking are rarely addressed for anything other than cosmetic repairs. This brings us to leaking nonstructural cracks. These cracks are often dynamic in nature. Repairing these moving cracks with epoxy can prove difficult and often results in mirror cracking (a process in which the structural movement causes the original crack pattern to reappear in the applied epoxy). Thus it is imperative to repair leaking nonstructural cracks with flexible polyurethane foam. Flexible polyurethane can move with the structure and still maintain a water-tight seal.

Leaking Cracks in a Parking Garage

A few years back I was asked by an engineer to look at a parking garage that had many leaking cracks. It turned out that it was previously "repaired" with epoxy, yet all the cracks and leaks had reappeared. This is a perfect example of why grouters should not use epoxy in leaking cracks. Another common mistake is to use a rigid (rather than flexible) polyurethane in a dynamic crack.

So the simple takeaway is to remember that epoxies are for structural repairs and polyurethanes are for waterproofing.

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In the United States, tilt-up construction is very common and the resulting joints are typically caulked. The vast majority of the time that is totally sufficient. But what about the joint you find yourself recaulking every six months to a year? While not the norm, they can be a real hassle and a thorn in your side. Enter Spetec PUR F400 and welcome to this blog post!

Spetec PUR F400 is a flexible hydrophobic polyurethane grout. Oakum is a fibrous jute rope that we soak the F400 in and then use to pack the wetted joint from the bottom up. This is a messy but simple process that leaves you with a full-depth seal/bond as opposed to the typical ¼” bond that is standard when caulking. The excess foam can be cut back and caulked to match the existing joints. Caulking is also required on the exterior as F400 is not UV stable, so the caulk protects the F400 from UV and makes the joint cosmetically match the other joints.

The same grout/oakum procedure described above can also be done for joints that are in constant submersion. Standard urethane caulk is not designed for constant submergence and while polysulfides are, they still can have problems with it. F400 is unaffected by wet, dry, wet/dry, or constant submerged environments.

These repair procedures can be applied to pipe penetrations as well. The "oakum soakum" method, as it's commonly known, is a tried and true methodology. But it is also one of the simplest methods for polyurethane chemical grout installation. I equate it to fingerpainting with chemical grouts.

Every grouting job has its unique challenges. Alchemy-Spetec's industry-leading tech support team is here to help! Call 404-618-0438 for assistance with your leak seal job today!

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I&I is a major issue that plagues all collection systems. What can be done about it? There are a number of large-scale and costly ways to address it but often these are overwhelming projects to start. So, let’s take a step back and start small with the manholes. A quick review of rain event data will help pinpoint problem areas. There may be numerous issues in a line, but remember we are going for easy manhole infiltration. Start popping manhole covers. We don’t need to look for every minor leak and the large leaks are easy to identify. Obliviously, flowing water is easy to spot but even if a large leak is not active there are normally clear signs of its existence. These signs include staining, native soils being washed in, or joints with bulging ramnecks. 

So now, with X number of leaking manholes identified, it is time to set a plan. Inverts and precast joints are often the biggest culprits. Often, they have been previously repaired with hydraulic cement. But hydraulic cement can’t deal with movement, and thus leaking cracks return. While hydraulic cement is cheap, repeating the repair process over and over is very expensive and means more confined space entries. Injecting the joints and inverts with a flexible polyurethane grout will provide a long-term repair, often longer than the expected service life of the manhole. Spetec PUR GT380 is the gold standard for these types of repairs, but at times a hydrophobic grout might be needed and thus Spetec PUR F400 would be the grout of choice. 

But what about older brick manholes? Often they are ripped out and replaced. Replacement is not always necessary, can be disruptive, and is very costly. Spetec PUR Highfoamer is an excellent choice for curtain grouting (the ideal application for sealing gushing leaks in old brick manholes). Its set time can easily be field adjusted and its 50x expansion makes it very cost-effective. 

So to review...

1. Perform a quick review of rain event data to identify potential leaks
2. Pop manholes to identify large leaks
3. Grout the defects for a long-term fix

The bonus round is to watch treatment costs drop due to less infiltration! 

Pro Tip: It is best to waterproof when the leaks are active.

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Concrete is the most common building material in the world. While it has high compressive strength, it does not have much tensile strength. It is only since about 1910 that rebar has been specified. Reinforced concrete can and does still crack. So does that matter? Yes, most of the time it does matter.

Epoxies Are for Structural Repair

Epoxies are commonly and very effectively employed to “weld” these cracks back together. End of story, right? Of course not. For structural repairs epoxies are correct and necessary, but what about non-structural dynamic cracking? Well first off, why do we even care if there is a non-structural crack? Sometimes we don’t, but when this non-structural crack is the source of water intrusion action is required!

Water intrusion, besides being unsightly can cause many problems. Slip hazards are an obvious one, remember that rebar we started adding back in the 1910s? It can corrode, per NACE it can expand about 7-8 times its size, causing spalling and even complete failure of the concrete. Epoxy repair of a dynamic non-structural crack does not end well. The crack is there to relieve stress and if it is welded together with epoxy then it cannot move to relieve the stress, which causes what we call mirror cracking (this is a new crack in proximity to the previous epoxy repaired crack). Now we are back to where we started and we wasted time, labor, and materials on a failed repair.

Polyurethanes Are Ideal for Sealing Leaks

Flexible polyurethane grouts are ideal for dynamic cracks. They will waterproof the crack but still allow the cyclic movement - thus no mirror cracking, no leaks, and no corroding rebar. There are two main categories of polyurethane grouts, hydrophilic and hydrophobic. Hydrophilic grouts have more flexibility (higher tensile strength) and better adhesion than hydrophobic grouts. So, the answer seems clear, choose a hydrophilic grout. Hydrophilic grouts are the first choice for most below-grade applications, but since they form an open crosslinking when they polymerize, they can dry out in arid environments. Hydrophobic grouts have a closed crosslink and therefore are unaffected by wet-dry cycling, but have less elongation and lower adhesion strength. So, if you're new to this, it's best to consult an expert when selecting a polyurethane for your leak seal job.

Technical Support for Leak Seal Contractors

When it comes to waterproofing with chemical grouts, product selection and application techniques will make or break a job. Good technical support ensures more production and less product waste. I have over two decades of field experience. I'm happy to share that knowledge in support of all your waterproofing needs, and I am just part of the most experienced grouting tech service team out there. We pride ourselves on education and training in the field, in the classroom, and online. Please let us know how Alchemy-Spetec can be of assistance to you. Call our tech support team today at 404-618-0438.

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In this post, I’m going to personally review two popular methods used to handle water leaks and infiltration. Both hydraulic cement and chemical polyurethane grouts are used in civil applications such as sewer pipe rehabilitation, tunnel or shaft construction, sealing leaking cracks in concrete structures, permeating soil to control the flow of groundwater, filling voids to stabilize soil, and handling common inflow and infiltration issues found all over the world.

This post will reveal the good, the bad, (and the ugly) when it comes to product selection and application. When considering chemical grout or hydraulic cement for your waterproofing needs, we will need to look at:

• Features
• Costs
• Applications

When it comes to waterproofing with chemical grouts, application techniques will make or break a job. There is a lot of misinformation out there, so I encourage you to carefully evaluate the content below and make the most educated decision for your upcoming projects. (For further assistance with that decision, feel free to call our tech support team at 404-618-0438.)

Before we continue, I’d like to briefly let you know who I am and what I do. My name is Charlie Lerman (a.k.a. The Grout Geek). I was the Technical Field Services Manager at two industry-leading polyurethane grout manufacturers for 18+ years before joining Alchemy-Spetec as the Director of Technical Services – Leak Seal Division. My full-time responsibility is to take care of your questions and uncertainties concerning waterproofing with chemical grout and alternative options. So when is it best to use hydraulic cement? When should you use chemical grout? Let’s compare:

What is Hydraulic Cement? Key Features

Hydraulic cement is inexpensive and easy to apply but its benefits stop there. It is a surface patch that is primarily applied to the negative side. It has a weak adhesion and thus is applied in a groove or similar cut. It can be used to shut down low-pressure leaks. Being that it is cement it has a low tensile strength which means just like other types of cement it will be brittle when it is cured.

Chemical Grout Features

There are two primary types of chemical grouts when it comes to crack injection, each unique in its composition and makeup: (1) acrylics and (2) polyurethanes.

1. Acrylic grouts are free of suspended solids and have extremely low viscosity. The grouts can change from a liquid to a solid in a controllable gel time ranging from 3 seconds up to 10 plus hours. The lifespan of acrylic grouts is estimated to be between 50-300 years depending on the method and application utilized. Acrylic grouts are hydrophilic, have about 500% elongation, and are only about 20 cps. These properties make them ideal for injecting hairline cracks. Alchemy-Spetec's Spetec AG200 acrylic injection resin is NSF 61-5 certified for contact with drinking water.

2. Polyurethane grouts can be grouped into two types: hydrophilic and hydrophobic. Hydrophilic grouts are usually single component formulations that react with water and cure to an expansive flexible foam or non-expansive gel requiring a moist/humid environment after curing. Hydrophobic grouts are expansive foams that require little water to react and can easily withstand wet/dry cycles. Hydrophilic foams expand 4 to 6 times their original volume, while hydrophobic foams can expand up to 40 times their original volume and may cure flexibly or rigidly. Alchemy-Spetec offers many polyurethane resins that are NSF 61-5 certified for contact with drinking water. The lifespan of polyurethane foam is estimated to be approximately 70+ years.

Both acrylic and polyurethane chemical grouts are injected into cracks or joints and thus are not considered a negative side waterproofing even though they are often applied from the negative side. Acrylic and flexible polyurethanes are designed to shut down active leaks and, because of their high tensile strengths, they can withstand the movement of a dynamic crack or joint. Because they are full-depth repair materials, they can also encapsulate rebar and thus help prevent corrosion, spalling, and thus structural failure.

Applications: When, Where, and Why

I cannot emphasize enough how helpful it is to speak with an experienced grout consultant and/or an experienced contractor when faced with the need to stop leaks or control inflow and infiltration. If you are looking for installation recommendations, a knowledgeable grout manufacturer should be consulted to assist with proper grout selection and installation methodology. I am available to assist with your next project. Call Alchemy-Spetec at 404-618-0438 and ask for the Grout Geek!

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