Alchatek Blog

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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Sealing Joints with Grout and Oakum

Whether injecting with a pump or a cartridge, it's always helpful to have AP Oakum on hand. Liquids will take the path of least resistance and oakum is very adaptable for controlling them. For example, joints are typically easier to inject than cracks, and precast joints are about as easy as they come in regards to injection work. They are also very common routes for water infiltration, whether in manholes, culverts, vaults, and tunnels. Since joint injection does not require the consistent pressure provided by electric injection pumps, you can often make these repairs with cartridges instead.

Simple and Effective Leak Seal Method

Time and time again, it is easy to look like a hero with nothing more than a cartridge of Spetec PUR F400, a handful of AP oakum, and a flathead screwdriver. Lastly, be confident. Don’t confuse high-flow leaks with high-pressure. When you're working less than 20’ below grade, you are only dealing with a few psi of pressure even if it is a high-volume leak.

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Sealing Steam Leaks with Polyurethane

One of the most high-tech veneer manufacturing companies in the United States chose Alchemy-Spetec to train their maintenance techs to stop a steam leak in their facility. You heard that right. Not liquid water, but steam leaks! Prior to milling the veneer, they heat the logs in a bank of steam vaults. Rather than tearing down/rebuilding these cracked, leaking vaults they opted to inject the cracks with Spetec PUR F400, a hydrophobic flexible polyurethane grout. Replacing the vault would not only have been a lot more expensive, but it would also have resulted in a costly interruption to their milling process. No one likes downtime.

Polyurethane Leak Seal Training

Saturday is the one day of the week that the vaults are offline, and that is when I conducted the complimentary field training for their employees, who had never done any injection work before. Within a few hours, they understood how to handle the grout, how to use the grout pump, and how to accomplish their injection work. They can now self-perform their crack injection as needed.

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I was a Machinist Mate in the Navy and thus almost all of my training was mechanically focused. One class I had was Electrical Theory for Mechanics. The quick summation by the Senior Chief instructor for it was "Electricity is magic and when the smoke comes out the show is over." Being on a submarine it was deemed a good thing to keep water and electricity separate. My first time ever using polyurethane chemical grouts was on a group of sixteen conduits entering a below-grade mechanical room. While electricians may understand the "magic" of electricity they often fall short as waterproofers. Combined with the fact the numerous electrical cables coming through a conduit can be notoriously hard to waterproof and it is a recipe for leaks and electrical problems. In this post, I'll share step-by-step instructions, along with a couple of photos from a recent job one of our customers completed in a San Francisco condo complex.

Oakum soakem is a kindergarten-skill level procedure that makes waterproofing these types of penetrations easy. I refer to this as fingerpainting with chemical grouts.

1. For PVC and HDPE pipe roughing the surface will increase the mechanical bond and is recommended.
2. Wet the application area.
3. Soak oakum in either Spetec F400, GT500, or GT380 resin until saturated.
4. Pack soaked oakum into pipe joint to be sealed. If necessary, pack multiple layers. Ensure it is under compression.
5. Allow grout to cure.

Often this is all that needs to be done, but it can be followed up with injection to fill the conduit if required.

1. Stab injection needle through the cured grout and oakum plug.
2. Inject grout.

Photo: Contractor on a recent job in San Francisco, addressing multiple conduit leaks with electric injection pump, a pail of Spetec PUR F400, and Oakum.

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Sealing Leaks in Concrete with Polyurethane

Water is RELENTLESS. Leaks appear in all kinds of structures, from underground parking garages to municipal treatment tanks to elevator shafts. Everything from fine hairline crack leaks to gushers can threaten the long-term integrity of the structure and surrounding property. Fortunately, pressure injection of polyurethane grout into the crack or behind the leaking wall (depending on the application) creates a durable and rugged positive side repair. A relentless solution to a relentless problem.

A wide variety of leak seal solutions are available to address almost any type of concrete leak. (Call the Alchemy-Spetec technical support team at 404-618-0436 for assistance in choosing a product for your specific project.)

Polyurethane Leak Seal Solutions - Crack and Joint Injection

Crack and joint injection products are generally used for smaller non-gushing leaks:

Spetc PUR GT380
Activates as Foam or Gel Depending on Amount of Water Added
Ideal for Manhole Rehabilitation

Spetec PUR GT500
Most Dry-Cycle Resistant Hydrophilic Grout
Ideal for Cracks with Intermittent Leaking

Spetec PUR GT350
MDI Based Grout
For Wet Dynamic Cracks & Joints

Spetec PUR F400
Flexible Hydrophobic Grout
Ideal for Dynamic Cracks & Joints

Spetec AG200
Acrylic Injection Resin
Used in Special Situations (Contact Alchemy-Spetec Support for More Info)

Polyurethane Leak Seal Solutions - Curtain Grouting

Curtain grouting products are generally used for gushing leaks or multiple smaller leaks in proximity:

Spetec PUR H100
Semi-Flexible
Ideal for Structures with Some Movement

Spetec PUR H200
2,050 psi Compressive Strength, Fastest Cure Time­­
Ideal for Soil Stabilization

Spetec PUR Highfoamer
50x Expansion
Cost Effective for Large Voids

Spetec Boom! Seal
Two-Component, High Expansion (35x), Hydro Insensitive
Used in Special Situations (Contact Alchemy-Spetec Support for More Info)

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A contractor in Atlanta was recently called in to seal off a rain-induced ceiling leak in a new construction high-rise penthouse suite. Sealing off the water intrusion from the roof above was not an option, due to the rooftop swimming pool directly above the penthouse. So, they had to get into the ceiling from the interior of the suite and repair the leak from the underside.

Powerful Polymers

The crew on this job injected Spetec PUR F400, a water-reactive, hydrophobic, flexible, single component polyurethane resin. This product is ideal for sealing off active leaks in cracks.

Painless Procedures

Leaking concrete structures can be permanently repaired with concrete crack injection & curtain wall procedures using water-activated polyurethane foam. Pressure injection of these liquid polyurethane resins forces the material into leaking cracks or behind leaking walls depending on the application. After the polyurethane injection is complete, the polyurethane resin rapidly reacts with water to form a watertight seal.

Rapid Results

In this case, the leak was shut down in less than two minutes. This all went down literally right before the new tenant was scheduled to begin moving in. (No pressure there!)

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What Causes Leaks in Concrete?

Imperfect Construction
Concrete construction is by no means a perfect science. New construction often requires Leak Seal treatment follow-up work. If the initial construction isn’t properly sealed at the time of construction, leaks are bound to appear sooner rather than later.

Weather and Wear
Concrete naturally decays over time. Exposure to extremely hot temperatures and extremely cold temperatures can take their toll over time. Even structures located in mild climates will begin to decay purely due to the aging process.

Unstable Soil
Unstable soil can undermine the integrity of concrete structures and cause cracks to appear. Loose soil has four main causes: soil erosion, poor compaction, freeze/thaw cycles, and biological decay. If soil is the main culprit, additional stabilization and slab lifting treatments may be required in order to prevent further cracks from appearing.

What is Curtain Grouting?

Curtain grouting is the process of injecting water-reactive resin behind the leaking wall in a grid pattern (from the negative side). The water on the other side mixes with the grout and cures to a solid mass covering the surface of the wall on the other side (positive side). In addition, you don’t have water pressure dislodging external “patches” over time, as can be the case with other methods.

Curtain grouting is often required when there are gushing leaks, multiple leaks in proximity, cracks cannot be identified, the walls are made of material that does not respond well to crack injection (such as masonry, stone, and CMU), or previous leak seal methods have failed.

The most well-known Alchemy-Spetec product for this application is Spetec PUR H100, a one-component, closed-cell, hydrophobic, water-reactive, solvent, and phthalate-free, low viscosity resin. If there are large voids involved, Spetec PUR HighFoamer (a similar product with a higher expansion rate) may be a more cost-effective option.

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Crack Injection Explained

Crack injection has many advantages over other methods.  For example, if you’re sealing a leak in a water tank, you can inject from the outside of the tank. So the tank can remain in service while you repair it. Having to dry a crack, like you do with epoxy resin, is not needed as this material reacts with water. The material also remains flexible at all times.

Crack injections can be applied in both vertical cracks and in horizontal cracks. With vertical cracks, it is imperative to start at the bottom of the crack and work your way up the crack until it is filled. This forces the material up and through the crack and will simultaneously push the water up and out as well. With horizontal cracks, injection can be started at either the left or right end.

Read more from Charlie Lerman's article Crack Injection Explained.

Curtain Wall Grouting Explained

Curtain wall injection is the process of drilling holes through a structure in a diamond pattern, then injecting the grout into soil on the other side. This procedure creates a curtain wall made of a resin/soil mixture that prevents water from getting back into the structure. It is often required if there are multiple cracks or leaks in a wall. Filling each individual crack may cause you to waste time following the water from crack to crack. Curtain wall grouting allows you to stop multiple leaks at one time and protects the structure on a long term basis.

This procedure was first performed in 1960 on a sewer manhole with a multiple leak problem. As described above, chemical grout was injected through to the outside of the manhole. This created a “positive side seal” (on the side the water was coming from), blocking water from penetrating the joints of the structure.

Read more from Charlie Lerman's article Curtain Wall Grouting Explained.

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Planners at Washington D.C.’s water utility, D.C. Water, decided to take proactive measures against potential flooding of their facility. Located right next to the Potomac, their facility could’ve been at risk in the event of an out-of-the-ordinary natural disaster. Determining that the main risk to the water supply in such a case would be permeation through sub-surface soil, they began installing a metal sheet pile wall deep into the substrate between the riverbank and the facility. However, in some spots they were not able to drive a sheet pile panel into the ground because of underground utility lines or rocky substrate. The planners called in LJS Waterproofing to create sub-surface grout walls in those spots to fill in the gaps.

Powerful Polymer

The LJS crew “constructed” these sections of the underground wall by injecting AP Fill 700. This is a single component, water-activated, hydrophobic, low viscosity, closed-cell polyurethane injection resin. This grout was used because it permeates the soil, fills small voids in the soil, and cuts off water flow.

Painless Procedure

LJS professionals used a Geoprobe to drive injection pipes into the ground (up to 33 feet in some locations). They then injected one gallon per foot using upward staging. The next injection point was 18 inches away from the first one. This process was repeated until a grout wall formed, filling the gap between the two adjacent underground sheet piles. For a large-scale job like this, LJS used the PolyShark single component grout pump.

Rapid Results

With solid, impermeable grout walls filling in the gaps, a sub-surface barrier between the riverbank and the drinking water facility was now in place. The planners at D.C. Water were very satisfied with this solution. LJS Waterproofing came through exactly in the way they had promised.

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The administrators of a church in Kingston, New York discovered water leaking through a wall into a hallway. The leak was located right next to the elevator. As water seeped into the elevator pit, it became flooded. Elevator pits often contain oil from hydraulic leaks in the equipment. Disposing of that oily water over and over can cost a property owner tens of thousands of dollars over time. The administrators reached out to LJS Waterproofing for assistance before the problem drove their budget through the roof.

Powerful Polymer

The LJS crew injected Spetec PUR F400 polyurethane grout to stop the water infiltration. This material reacts with the water inside the concrete cracks, curing to form an impenetrable seal. Chemical grouts are the most reliable way to shut down leaks in concrete.

Painless Procedure

1. Concrete crack injection with polyurethane resin is a five-step process:
2. Drill the injection holes.
3. Flush debris out of the holes with water.
4. Install the injection port.
5. Flush the crack with water.
6. Inject the resin.

For a complete overview of the crack injection process LJS professionals used on this job, see the Alchemy-Spetec blog post series 5 Steps of Concrete Crack Injection.

Rapid Result

The crew finished the repairs in a timely manner, saving the church a great deal of money in the process. The hallway is now completely dry and the elevator pit is no longer flooding. An ounce of prevention, in this case, was definitely worth a pound of cure!

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