Alchatek Blog

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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As the Director of Technical Services for the Leak Seal division at Alchemy-Spetec, I often find myself assisting customers with some interesting jobs. Such was the case when I was called in to consult with a contractor who was sealing a leak in a historic district below-grade, multi-course brick wall. As is often the case with below grade, historic spaces, water infiltration was unsightly, gave off a musty odor, and was damaging to finishes. This was a very old brick wall, approximately 8 x 15 feet in size and at least three courses thick. The owner wanted to find a way to waterproof this vintage brick structure while at the same time preserving its unique appearance. In addition to the water flow issue, the leaks were causing mold/mildew on the walls.

We proposed injecting Spetec PUR AG200, a high-strength elastic acrylic injection resin, into the cementitious grout between the bricks where the water was migrating through. In order to monitor the efficacy of this leak seal job, we employed the QP Factor® leak seal testing and quality control system. As stated on our website, “The QP Factor® system offers quantifiable water flow, pressure, and flow/pressure metrics before and after leak seal injection that will provide clients, contractors, and design professionals the industry’s first patented method for proving Leak Seal® success.

The method of testing requires additional drill holes to be placed at pre-determined locations along the crack, joint, or substrate being sealed. Prior to injection of chemical grouts such as Spetec PUR F400, Spetec AG200, or Spetec PUR GT500, the test hole is connected to a digital touch-screen device that is calibrated to provide water pressure, flow, and flow/pressure information that is extractable in excel format from a convenient USB port.”

We ran the QP Factor® system on three test areas in the wall before beginning the injection process. This revealed to us the amount of water that was flowing through the wall. After injecting Spetec PUR AG200 into the existing cementitious grout around the bricks in two of those test areas, we ran the QP Factor® tests again and realized that wouldn’t have to inject the third area due to the efficacy of the Spetec PUR AG200.

Screenshots from the QP Factor program...

In addition to stopping the water flow, sealing the leaks made it possible for the bar owner to keep the walls clean in appearance. See the treated area of the brick wall vs a non-treated area.

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3M Scotch Guard 5600 can still be found in engineer specifications for a variety of leak seal applications. However, this product is no longer manufactured. Fortunately for anyone using these specs, Spetec PUR GT500 is available a substitute.  See the details below and call us at 404-618-0438 with follow up questions!

Uses for Spetec PUR GT500:

• Sealing cracks in concrete structures through pressure injection.
• Sealing hairline cracks, expansion joints, wide cracks, pipe joints, pipe penetrations.
• Saturating dry oakum to create a flexible gasket for sealing pipe penetrations, joints and larger defects in concrete structures.

Advantages of Spetec PUR GT500:

• Non-flammable. Does not contain any volatile organic compounds
• No catalyst required.
• Tenacious bond to wet concrete.
• High elongation.
• Thin enough to penetrate tight cracks.
• Hydrophilic.
• Phthalate free (more environmentally friendly).
• Certified to NSF 61-5 (Approved for contact with drinking water).

If you're working with old specifications designating 3M Scotch Guard 5600 for leak seal applications, you can definitely use this product as an alternative. Engineers writing new leak seal specifications for the uses mentioned above should also consider including Spetec PUR GT500. If you have any questions, please don’t hesitate to call our industry leading technical support team at 404-618-0438.

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Major water infiltration in precast manholes often occurs at the pipe penetrations. Failure to seal these leaks quickly could lead to the loss of thousands of dollars. It can also suck in soils and fine particlesThis process creates voids outside the manhole. With time, these voids grow larger and become sinkholes.

The typical method of sealing manhole pipe penetrations is using cementitious grout. This method may be effective at first, but you'll eventually notice cracks and infiltration again because it can't withstand the slightest movement of the pipe.

We recommend you use a combination of Spetec PUR GT380 and AP Oakum. The GT380 is a highly flexible polyurethane grout that allows movement between the pipe and manhole. Combine it with the AP Oakum which is an oil-free dry jute rope, and you can take care of large and irregular-shaped defects.

The installation steps are as follows:

1. Clean the surfaces on which you want to apply the Oakum. Wet them down if necessary, so they can react with the resin.
2. Cut the oakum into appropriate lengths if necessary.
3. Place oakum in a clean container (5 gallon/18.9 liter pail or plastic bag) and saturate with resin. Give time for the resin to soak into the oakum.
4. Using gloved hands, pull a section of oakum through a loose set to squeeze out excess resin.
5. (Optional Step) Dip the oakum in a pail of water to begin the reaction process of the resin. Soon, the resin will expand.
6. Pack oakum into leaking defect around the pipe using a screwdriver, wooden dowel, or other mechanical device sized appropriately for the joint, crack, or defect.
7. After the resin has cured, you may inject additional resin via a grout needle directly through the oakum or by drilling holes through the concrete behind the oakum.
8. Leave the material to cure overnight before attempting to trim the excess foam.

With the Spetec PUR GT380 and AP Oakum combination, your work will last up to 50 years - way longer than it would if you used hydraulic cement.

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What happens when a joint in a precast manhole begins to leak? The answer is it may as well be leaking money.

About $22k could be lost yearly because of any ONE manhole leak at the rate of 10 gallons per minute. In the U.S, there are approximately 20 million manholes, and many of them have OVER 10 gallons of infiltration a minute. You can imagine the potential loss.

Generally, manholes leak because of either movement and settlement after installation or just plain bad installation. A leak can happen at any time. Thankfully, Alchemy-Spetec offers a quick and effective solution to this problem.

You can seal precast manhole joints using Spetec PUR GT380. It is a hydrophilic polyurethane material that cures to form a gel or a foam. Because it's a single-component material, you can install it easily without the need for mixing. It can easily penetrate joints before it eventually cures into place, thanks to its low viscosity.

Installation is simple.  There are only four steps:

1. Drill holes. Typically, four per barrel joint.
2. Flush the holes.
3. Install your injection port.
4. Inject the resin.

With Spetec PUR GT380, you can have confidence in your work because this is a durable, long term sealing solution that holds up against the harsh sewer environment.  And your clients will be delighted to stop losing money from leaking manhole joints.

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In this post, we’re profiling Spetec PUR GT380. This hydrophilic polyurethane gel injection resin is your best option for shutting off water leaks in concrete, brickwork, and sewers where movement may occur. You can also use Spetec PUR GT380 for curtain grouting behind tunnels, concrete, and sheet piling. Due to the product’s low viscosity, you can also use it to cut off water leaks in a variety of foundations, including diaphragm walls, piling sheets and secant piles.

Advantages of Spetec PUR GT380

• Highly flexible and ideally suited for structures with high probability for settlement or movement.
• One component hydrophilic polyurethane resin, additional mechanical water shut-off through expansion after curing.
• Versatile form, adjustable with the amount of water added. Can cure to a rubbery foam (200 to 500% water) or a stable polyurethane gel (500 to 700% water).

We advise pairing the resin with the following accessories: a Spetec Pump Cleaner, AP Soak 130, Oakum, mechanical ports, and a single component electric injection pump.

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Chemical grouts have an amazingly diverse range of properties. This makes them incredibly useful for all types of waterproofing, soil modification, and structural repairs. This wide range of characteristics means that there is no one size fits all grout out there. But I get ahead of myself. Before one can select a chemical grout for a repair it is necessary to understand not only the asset to be repaired but also how and why it is failing and/or leaking. There are numerous methodologies that can be utilized to determine what is going on, but before one can start the troubleshooting one needs to understand the structure's design.

This is why I love articles like this one from PileBuck.com. It gives a good overview of seawalls and bulkheads. These structures are often the frontline in our war against erosion and thus require periodic maintenance. We at Alchemy-Spetec are committed to providing cost-effective, high-quality grouts tailored to the precise needs of the project. We know that a quality grout is just the beginning and we follow-through with the most experienced technical support in the industry. Enjoy the article...

Along bluffs and coastal shorelines, various structures are often necessary to protect beaches from wave action, or to retain fill or in situ soil.  There are three primary structure types that can be utilized to accomplish these goals, including protective materials laid on slopes, known as revetments, and vertical structures, which are classified as either seawalls or bulkheads.

Revetments are typically constructed of stone or other durable materials to provide protection for designated slopes.  They are built with an armor layer, a filter layer or layers, and toe protection.  The armor layer can consist of interlocking structural elements designed to form a geometric pattern, or a random mass or stone or concrete rubble.  Next, a filter layer will ensure drainage and protection of the underlying soil.  Finally, toe protection will offer stability against undermining at the base of the revetment.

While bulkheads and seawalls are both types of vertical structures used to protect coasts, they have different purposes.  Bulkheads are used to retain or prevent the sliding of land, with protection of the upland area from wave action as a secondary consideration.  In contrast, the primary purpose of seawalls is to intercept waves.  Bulkheads can be cantilevered, anchored, or gravity structures, with their use limited to areas where wave action can be resisted by the types of materials used in these respective designs (such as sheet piling or rock-filled timber cribs).  For areas where intense wave action exists, massive concrete seawalls are the more appropriate choice, with either a vertical, concave, or stepped seaward face.

Read the rest at PileBuck.com...

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AP Oakum is an oil-free dry jute rope which can be used dry or soaked with Spetec PUR GT500, Spetec PUR F400 or any other Spetec water-reactive resin to seal leaks in concrete structures. The oakum rope works well dry to drive into cracks as a temporary seal to allow injected resin time to cure without washing out. Here’s an overview of the installation process:

Preliminary Analysis

Determine if the large crack or joint is structural or cosmetic. If deemed structural, consult an appropriate engineer. Oakum is typically utilized in conjunction with water-reactive chemical grouts in leak-sealing applications. Void filling of these spaces can also be achieved through similar application techniques and appropriate product selection.

Preparation of Substrate

Remove all existing sealant, debris, or contamination of any kind. In large openings, inspect for loose concrete or anything that would prevent insertion of oakum into the desired depth and location.

Preparation of Product

Firstly, cut oakum into desired lengths and segments. Pre-mix hydrophobic or hydrophilic chemical grouts per manufacturer recommendation in a separate container taking note of working times and reaction times. Once the material is mixed, quickly, and fully soak the Oakum in the mixed chemical grout. Place the saturated oakum to the desired location.

Preparation of Personal Protection Equipment

Oakum is typically manually installed. Be sure to wear full hands, arm, face, and eye covering at
all times. Chemical grout can drip/spill cover anything with which it comes in contact.

Application of Oakum

1. Clean the surfaces to which the oakum will be applied. Wet the surfaces down if necessary, to react with the resin.
2. If necessary, cut the oakum into appropriate lengths.
3. Place oakum in a clean container (5 gallon/18.9 liter pail or plastic bag) and saturate with resin. Allow time for the resin to soak into the oakum.
4. Using gloved hands, pull a section of oakum through a loose set to wring excess resin from the oakum.
5. Optional Step: Dip the oakum into a pail of water to begin the reaction process. This will begin the reaction process of the resin. This step causes the resin to begin to expand.
6. Pack oakum into the joint, crack, or other defect using a screwdriver, wooden dowel, or other mechanical device sized appropriately for the joint, crack or defect.
7. After the resin has cured you may inject additional resin through a grout needle directly through the oakum or by drilling holes through the concrete behind the oakum.
8. Allow the material to cure overnight before attempting to trim the excess foam.

Brief Video Clip

Here's a brief video, taken from my trusty Grout Geek Helmet Cam, of me packing oakum into a gushing leak.

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We all know the destructive power of earthquakes, hurricanes, and other forces of nature and while I was aware of expansive soils, I had no idea the amount of damage they cause. We at Alchemy-Spetec focus on industry education, so I am pleased to share this video about expansive soils from Grady Hillhouse at Practical Engineering.

Here's a text excerpt to whet your appetite...

"When most people think property damage, they think about natural disasters. But what if I told you there’s a slow-moving, geologic phenomenon that causes more damage in the United States than earthquakes, floods, hurricanes, and tornadoes combined?

Hey, I’m Grady and this is Practical Engineering. Today we’re talking about expansive soils.

Certain types of clay soils change their volume depending on moisture content. They swell when they get wet and shrink as they dry.  This is a microscopic mechanism where the shape and arrangement of the molecules actually change according to the amount of water mixed in. And large portions of the U.S. Gulf Coast and Great Plains have these kinds of soils. If you’re starting a foundation repair or road paving business, this is an important map for one very good reason – expansive soils break stuff."

Click the video below for more...

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