Alchatek Blog

Spanning the Pithlachascotee River in New Port Richey, Florida is the Madison Street Bridge. Built in 1985, this structure was buttressed with four semi-circular seawalls at the base of each footing in the year 2000.

Over the years, tide fluctuation caused soils to wash out from underneath the seawalls. This caused the heavily used sidewalks on top of the walls to crack and settle, allowing even rainwater in. Without an alternate way for pedestrians to traverse the bridge, this structural problem quickly became a critical public safety issue.

Powerful Polymer

To rapidly address the problem a certified contractor relied on AP Fill 700 and its NSF 61-5 certification (approved for contact with drinking water). The rapid expansive properties of this semi-rigid hydrophobic resin made it the optimal solution for painlessly filling the voids that had developed in the seawall and stopping the erosion beneath the sidewalks.

Painless Procedure

To rapidly address the problem a certified contractor relied on AP Fill 700 and its NSF 61-5 certification (approved for contact with drinking water). The rapid expansive properties of this semi-rigid hydrophobic resin made it the optimal solution for painlessly filling the voids that had developed in the seawall and stopping the erosion beneath the sidewalks.

Rapid Result

Stopping the leaks in all four seawalls only took a few days. More than a year later the seawalls are still as good as new.

Want in-depth info on polyurethane seawall repair?

The Problem

As tidal flows rise and fall, water pushes its way in through cracks, joints, and defects in seawalls.  The water pushes in on incoming tides and flows out on outgoing tides.  As the water flows out, it carries sand and soil with it which causes undermining of the structure, voids to form, and deteriorates the structural integrity of the seawall.  This cycle is exacerbated during periods of heavy rain which continue the outflow of soil.

The Solution

AP Fill 700 is a semi-rigid hydrophobic polyurethane foam that reacts with water or moisture in the soil and expands to fill voids while it permeates sandy soil to form a solid, strong, watertight mass.  It has been used extensively in seawall applications to seal cracks, voids and defects as well as for filling voids and stabilizing the soil.

The Process

AP Fill 700 can be injected through pipes directly into voids and loose sandy soil using a single component pump (airless sprayer or double diaphragm pump).

Step 1:  Insert pipes down to the lowest level to be injected.  This can be done through driving the pipes mechanically, water jetting, or air jetting them down.

Step 2:  Ensure the soil has enough moisture content to cause a reaction of the AP Fill 700 (slightly damp to saturated).

Step 3:  Blend catalyst with AP Fill 700 to desired level.  Typically, between 2% and 5% AP 106 Catalyst will be sufficient.

Step 4:  Connect the hose from the pump to the injection pipe.  The hose should have a ball valve to control the flow of the material.

Step 5:  Inject AP Fill 700 either at a pre-determined rate (rule of thumb is 1 gallon per vertical foot) or until sufficient back pressure is established.

Step 6:  After each “point” is injected, raise the pipe 12” and repeat the process.  Once the pipe is within 24” of the surface you will probably get material flowing back to the surface (known as “refusal”).  Stop at this point and move to the next pipe.

Step 7:  Repeat this process until the entire area has been injected.

Note:  A containment barrier should be used on the water side of the seawall to capture any foam that leaks out of the seawall during the process.

Note:  Check valve type drains may need to be installed in the seawall after injection to allow water from heavy rains to vent out and reduce pressure on the seawall.  These drains will allow water to flow out, but not soil.

Want in-depth info on seawall repair procedures and products?

Repair sea walls instead of replacing them by stopping high flow leaks, filling the voids behind concrete structures and binding loose soil with:

AP Fill 720 & AP Fill 700 — innovative, cost effective, water activated, low viscosity, simple to use closed cell polyurethane injection resins.

Proven Strength

• Because these foams are impermeable to water once in place, the likelihood of future erosion is vastly diminished versus other commonly used fill materials.
  
  
• Originally developed over 30 years ago, and continuously improved since, this technology has one of the longest histories of success in the field among engineering uses of polyurethane foams.

Environmentally Friendly

• Phthalate free.
• Approved for contact with drinking water.

Quick Set Time vs Cement Grout

• AP Fill 700 & 720 foams set in 10 minutes or less.
• Cement grout takes hours to days.

Differences Between 700 and 720

• 720 has a higher expansion ratio and is more flexible when cured.
• 700 has a lower viscosity, so it works better in cooler temperatures.

Want a complete technical breakdown of AP Fill 700 & 720 for seawall repair?

When it comes to seawalls, there is a lot more to learn than meets the eye. A seawall is like a living, breathing thing: especially in the way that it is designed to function. But like all living breathing things, they have a finite lifespan. For many of them, it's a mere 20 – 30 years. Depending on where you live, replacing a seawall can cost anywhere from $150 to $500 per foot. That's enough for some homeowners to choose to move instead of rebuilding their seawalls. Today however, signs of seawall distress can be solved before they get too bad through the application of polyurethane grouts to seal leaks, fill voids, and stabilize the surrounding soils.

Although seawalls are found around lakes and rivers, it is around the ocean that they are put to the most difficult test. Salt corrosion, tidal action, currents, boat wakes, storm surges and sometimes hurricanes all deliver a constant beating on the seawall. But many of the forces are also coming from the landward side of the wall. Every time it rains or the irrigation system runs, and every time the tide goes out; all of the groundwater above the waterline has to vent or equalize. Tremendous pressures can build up if that water is trapped and cannot make its way into the sea or the storm water system.

Correct construction of a seawall will include a drainage system to handle the bulk of the water that comes from rain in addition to check valves, weep holes, or seams to handle the daily influx and outflow from tide and wave action. Although these systems are designed to retain the soil behind the seawall, over time the materials degrade or can be disturbed by settling. The result is a loss of soil and the inevitable sinkholes and / or low spots that will occur along the wall. Other times, the weep holes and vents become clogged and the water has no way to escape except to force its way down and out from underneath the base of the wall. When this occurs there will again be sinkholes and sometimes wall failure.

When signs of sinking ground are observed, you can almost be sure there are voids below that are unseen and dangerous. Sometimes these voids can extend below an adjacent patio, dock, or pool deck, causing those to sink and crack. Anticipating those problems is key to keeping those problems at bay, and proper application of polyurethane injection is the solution. AP Fill 700 is a lightweight injection resin that can be injected along the wall where the settling is occurring and generate multiple benefits. It will seal any leaks along the wall, fill the voids that have occurred, and mix with the soil to form a solid, impermeable mass. Combined with proper drainage, this method can extend the life of your seawall.

If you live along the water, it is always going to be man against nature. That seawall is keeping your property from damage and from disappearing altogether. Advanced polyurethane technology from Alchemy-Spetec is a key to extending the life of your seawall. It's fast, clean, easy to install, and most of all, effective.

Want in-depth info on seawall repair procedures and products?

I met with a contractor today who does residential slab lifting and for some reason we ended up talking about incoming leads and how to prequalify them. Every slab lifting or foundation contractor has experienced driving for hours to look at a potential job that turns out to be a wasted trip. Every property owner has probably taken time off from work to meet a contractor who wasn't the right fit either. It's not anyone's fault but it can be avoided, saving both the contractor and the property owner valuable time.

I thought it might make a good blog topic: how to technically evaluate an incoming lead before sending a salesperson out to do a site evaluation and estimate.

Here are some prequalifying questions to consider asking a property owner:

1. Can you text me or email me a picture of the sunken slab, stairs, pool deck, etc?
   This will tell you a lot because pictures may reveal that the concrete is too fractured for lifting. If so, you'll save yourself a trip. You may also notice some impediments to the lifting process, like brickwork or bound slabs. Pictures may also reveal the cause of the problem, like erosion caused by poorly directed roof drains. With this info you can start developing a plan right away (if you decide on a site evaluation).
   
   
2. How long has this been going on?
   It's important to ask the owner how long the settling has been going on. If it is recent and happening at an accelerated rate, that may indicate an entirely different problem than a slab that has settled over a period of years. Settling related to erosion and compaction issues, as well as buried organic material, usually occurs gradually. Broken pipes and sinkholes, on the other hand, usually cause rapid sinking and need attention immediately. It might be better in these cases to recommend a plumber or geotechnical engineer first before going to look at the sunken slab.
   
   
3. What information is available?
   Has anyone else been out to look at it, what were their findings, and are there any available engineering reports? This is pretty self-explanatory. Information is extremely helpful on geotechnical jobs whether it is data from ground penetrating radar, soil borings, penetrometers (DCP), etc. Even local knowledge of the property can be very helpful. Were any new buried utilities put in, or were there any adjacent property developments where de-watering was incorporated? This information may also keep a contractor from making a mistake by quoting on something they are possibly not qualified to execute. As Clint Eastwood (I wish) once said, "Slab lifting contractors must know their limitations".
   
   
4. Is this property for sale or going on the market?
   This is a sensitive subject to write about because some of our contractors do get leads from real estate experts and property owners. Often there has been an inspection and the report indicates a tripping hazard or a settling issue. The owner and potential buyer will use the repair estimate to negotiate on the sale price and no work ever gets done. It's fair to ask if this is just a quote required for the sale of the property or if there is a real intention of fixing the issue.
   
   
5. How far down is the slab or foundation?
   It takes a certain amount of polyurethane to lift a slab. Sometimes you have to accept that a slab that is down 12 inches may be more affordably replaced than lifted. However, sometimes a slab that's down several inches may be in a location where demolishing it and bringing in new concrete is disruptive. The polyurethane may be the best and only answer; one of the things that makes it great.
   
   
6. Are you the owner?
   I can appreciate a renter's concern about concrete settling but you obviously need to talk to the owner. There have been many site visits made on request of a renter to be used as a complaint against the owner. I'm not saying these are illegitimate issues but they deserve to be evaluated carefully.

In addition to asking the questions above, you'll want to keep these two points firmly in mind:

1. Stay focused on the repair.
   In the concrete repair, soil stabilization, and slab lifting business, contractors are often called in when something is going wrong. Something is leaking, sinking, cracking, etc. When evaluating a job site it is always a good idea to consider what you say and what you propose to the client. It is good policy to focus on the repair rather than give your opinion on why something happened or why the engineer recommended a repair method. That is context sensitive obviously, but sometimes there are litigation issues that could be pending.
   
   
2. Make sure they know you're using polyurethane rather than cement grout.
   Last of all it's always a good idea to make sure the client understands you are using polymer technology and that you are not a mudjacking outfit. Polyurethane slab lifting with the AP Lift series of foams is cleaner, permanent, it doesn't shrink or wash out - and our certified contractors are better looking, ha ha.

Want more information on polyurethane slab lifting?

Perhaps the most misunderstood functionality of mechanical packer design is the ball-valve placement.  The ball-valve placement is important because this is the functional element that keeps chemical grout in the substrate as it reacts and creates the density required to adequately seal the substrate.  It is an applicator error to remove the packers prior to full product cure.  Top-mounted zerk-valve packers allow for port-to-port travel observation.  Port-to-port travel is injecting one packer until chemical grout is observed exiting the next packer which does not have an anti-return zerk-valve installed.  Once the material is observed coming out of the next packer, the zerk-valve can be installed, and the process repeated (see FIGURE 7).  This is only possible with top-mounted ball-valve placement.  Another benefit of the top-mount packer is the ability to replace the standard zerk-valve with a button-top-valve (see FIGURE 8).  Button top valves, as mentioned above, minimize leakage with a more secure connection to the packer that doesn’t allow the coupler/packer connection to flex (see FIGURE 9).

Bottom-mount ball-valves (as seen below FIGURE 10) are less common in the industry.  The main benefit of bottom-mount ball-valves is the immediate removal of the top shaft following injection, and subsequent patching of the drill hole with the ball-valve still in the substrate.  Bottom-mount ball-valve packers commonly have a bit more leakage and excess chemical grout as the shaft, above the ball-valve, is full of unreacted and unconfined chemical grout.

Alchemy-Spetec supplies a complete offering covering all of the functionalities detailed in this brochure.  Below is a table detailing bottom-mount options and top-mount options.  Note: All top-mount options can be converted to button-top style with by adding the equal quantity of Button-Top Fittings, ACP-2203.

Want more information on mechanical packers? 

Mechanical Packers come in many types. In the concrete repair industry, contractors will find plastic, steel, brass, aluminum, zinc, and other metal alloys. The most commonly used type is steel. Steel offers the benefits of strength and resistance to oxidation through chemical grout oxidizing components found in grouts such as acrylics. Brass and Aluminum packers are weaker and allow for the shaft to be broken off by hammer for more timely patching efforts following injection. However, most Quality Control Managers and clients will require the removal of all metal from the substrate prior to patching. The chosen method of removal is the choice of the client and/or design professionals.

There are two types of plastic packers used (see FIGURE 4). The 5/8” (16mm) button top packer is used for high volume applications and for applications in which a button-top coupler is preferred to minimize leakage. The free-floating ball in the middle of the packer acts as an anti-return valve. A 5/8” (16mm) plastic sleeve is inserted first, with the threaded plastic base then screwed into compression via the hex head top.  Another common port used is the 3/8” (10mm) plastic bang-in, or hammer-in port. These ports are simply inserted into a 3/8”(10mm) drill hole aided by the force of a hammer. The soft nature of the plastic allows the concrete to bite into the sides of the packer creating a compression seal. Because plastic packer compression is achieved through plastic to concrete friction, the overall pressure tolerances are typically lower than that of the mechanical packer counterpart.

Aluminum packers have recently become more prevalent in the industry due to the combination of economical pricing with the benefits of mechanical packer pressure tolerances (see FIGURE 5). Due to the softness of the components, however, these packers have been known to strip threads at times. All functionality considered, aluminum packers do offer a reasonably price alternative to the steel mechanical packers.

Alchemy-Spetec continues to offer a popular heavy-duty ½” (13mm) and 5/8” (16mm) packer with a soft grade of rubber and washer on the top of the packer that adds extra friction and bite to the concrete when tightened. The heavy-duty packer offering is in steel (see FIGURE 6). These heavy-duty packers are top-mounted ball-valve style and can be converted to button-top valve (see next section and below).

Want more information on mechanical packers?

Due to a driver shortage in the shipping industry, non-guaranteed
shipments are being pushed to the back of the line, re-routed, or
even placed on rail.

When you choose guaranteed service, we have much more leverage
in the event delays do occur.

We now recommend choosing guaranteed service if your order is
time sensitive and ordering at least a week in advance when possible.

Click here to view a USA Today article on the current driver shortage
in the shipping industry.

Mechanical Packers are most commonly used in poured concrete substrates. In adequately consolidated poured concrete structures, the drill hole itself acts as a channel through which the chemical grout will travel as it reaches the cross-section of the crack or joint. In these conditions, only the entire rubber shaft of the mechanical must be recessed into the drill hole to create an adequate compression seal. In the example of a 3” long packer, this would leave approximately 1.5” of metal shaft for connection access from the coupler that connects the hose line to the mechanical packer. However, it is common to experience micro-spalling at the point of drilling as the drill catches the 45-degree drill line. In these cases, the packer must be set even further into the concrete to ensure the rubber is fully recessed into the drill hole. This condition decreases the length of shaft accessible at the face of the substrate for connection to the coupler and can present challenges for the applicator. For this reason, it is advised to utilize 4” or 6” long packers in deteriorated or defective concrete substrates (see FIGURE 3). 

Length can also be advantageous when the contractor is attempting to inject the material to a specific point within the substrate. For example, it may be desirable to deliver chemical grout to the backside of a 4” substrate, or to a certain depth for a pipe penetration, or to account or unknown consolidation of the concrete within the drill hole channel that could lead to lateral travel of chemical grout to undesired locations within the substrate. Each job-site and substrate condition is different, and length of mechanical packer can provide the contractor with more options and ultimately a more effective delivery of chemical grout.

Mechanical Packer diameter is relevant for two reasons, 1) this dictates the size of the drill hole required, and 2) the overall surface area of the rubber in the drill hole is a key contributor to the pressure tolerance of a mechanical packer. 

1. Size of drill hole considerations: Industry standards require 45-degree drilling to insert mechanical packers to a crack depth that is ½ the thickness of substrate.  For thin substrates, for example 6” thick slabs, drilling at a 45-degree angle with a 5/8” drill bit may cause spalling and damage to the surface above the drilled angle as the outward heave force from the passage of the drill is greater than the strength of the concrete at that location, resulting in concrete spall and cracking damage at that location.  For these applications, Alchemy-Spetec offers 5/16” (8mm) and 3/8” (10mm) diameter packers (see FIGURE 1).  

   The smaller cross section of drilling produces much less heave force against the face of the concrete and offers much better results when drilling into a thin concrete substrate. 

   Post-tension structures and/or structures with a significant amount of rebar also present an obstacle when drilling.  By reducing the size of the drill bit by 40-50%, the contractor also decreases the probability of drilling into rebar or post-tensioning accordingly.

2. The tradeoff for smaller diameter is a decrease in pressure tolerances.  Common ½” (13mm) or 5/8” (16mm) mechanical packers tolerate spikes in pressure greater than 4,000psi (see FIGURE 2).  At 4,000psi, packers and ports can present a significant job-site hazard as they can exit the drill hole at dangerous velocities.  While injecting at these pressures are never recommended, a ½” (13mm) or 5/8” (16mm) rubber base on the mechanical packer will prevent blow-out significantly better than the 5/16” (8mm) or 3/8” (10mm) counterpart.