It's a scene that many homeowners dread: glancing out the window one day to discover large sunken areas in your once-smooth concrete driveway. These uneven sagging sections seem to appear out of nowhere, but in reality, are the result of a very common problem.

Understanding Sunken Slabs

Sunken concrete slabs occur when the ground underneath the driveway begins to settle or wash away. The weight of vehicles driving over the same area day after day also contributes to gradual sinking. As the support below the concrete erodes, sections of the driveway start to dip and crack. Water can then seep underneath and cause further erosion, leading to more pronounced sinking.

If left unaddressed, these sunken concrete slabs will only continue to deteriorate. The uneven surface also creates hazardous conditions for both vehicles and pedestrians. Tires, mufflers, and undercarriages get damaged from scraping against the raised edges of the sunk sections. Anyone walking across the driveway risks twisting an ankle or tripping.

How It Affects Your Driveway

In addition to safety concerns, sunken concrete slabs negatively impact your home's curb appeal. The uneven sunken appearance looks unkempt and diminishes the value of the property. The problem will likely only worsen over time without proper repairs.

Identifying the Problem

Homeowners will first notice sunken concrete slabs when large dips or cracks appear in the driveway surface. There may be audible clunks as vehicles pass over the uneven sections. Pitting, crumbling edges and pooling water are other telltale signs of sinking.

The issue can originate in small areas and spread or may occur simultaneously across large sections. Careful inspection when dry can help determine how much of the concrete is affected. Addressing sinking slabs as soon as the problem is spotted will provide the best repair results. Ignoring sunken concrete driveway slabs risks further deterioration and safety hazards. 

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Unstable soils present significant challenges in civil engineering projects. Whether caused by erosion, improper compaction, freeze-thaw action, or decay of buried organic matter, loose and shifting soils undermine structural integrity. Together, these mechanisms prevent soil from remaining firmly in place. This necessitates methods to stabilize and strengthen the matrix. Geotechnical engineers must find solutions to reinforce the substrate and restore load-bearing capacity.

Polymer injection grouting offers an innovative approach, transforming loose soil into a strong, consolidated mass. These polymeric resins permeate porous soils and compact denser soils, then expand and cure in place. The resulting soil-polymer matrix has high compressive strength, stopping subsidence, erosion, and migration of fines. Alchatek's standard soil stabilization products and deep soil stabilization products provide specification-grade stabilization.

Polymer Foam Stabilization Mechanisms

• Permeation of loose sediments, gluing them into a firm matrix
• Displacement of water from eroded zones, reversing further erosion
• Filling of void spaces from decayed organics or poor compaction
• Adhesion to soil particles creates a strong substrate

Additionally, these foams are NSF/ANSI/CAN 61 certified for contact with potable water supplies. This enables environmentally safe use.

Performance Characteristics

Polymeric foams provide exceptional soil stabilization and foundational reinforcement. Key advantages include:

• Ability to permeate and treat loose or unstable soils in situ without excavation
• Ability to compact dense soils such as clay
• High compressive and shear strength, restoring structural load capacity
• Permanent stabilization without ongoing maintenance requirements
• Mitigation of subsidence or erosion with bonded soil matrix

When applied correctly, polymeric foams offer lasting soil stabilization and ground improvement. Alchatek case studies document successful performance for applications including commercial, industrial, new construction, and other geotechnical engineering projects.

Additional Guidance for Geotechnical Engineers

Specify these advanced soil grouting products to permanently resolve instability issues. They deliver rapid installation, minimal invasive work, and results that last. Let us provide guidance on product selection, specs, and installation techniques for your next soil stabilization project. Polymer grouting is an innovative, low-impact way to reinforce unstable ground.

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Carrington Woods Lake Dam is located in Baldwin County, Georgia. A consulting firm collaborating with a general contractor called in geotech specialists Atlas Structural to stabilize an abandoned below-grade culvert pipe that had deteriorated over time. The pipe ran underneath a spillway. With supporting soil migrating into it, its unstable condition threatened the integrity of the structure.

Powerful Polymer

The technicians chose single-component AP FIll 720 for the job. The deteriorating pipe was 100 feet long, and due to the circumstances at the site, grouting could only be done from one end. Getting a two-component foam 100 feet up a pipe before it cured would have been impossible. AP Fill 720, featuring a very flexible set time adjustment range with the catalyst, allows technicians to pump the material for great distances before it starts to react and cure.

Painless Procedure

AP Fill 720 does not have to be heated and only needs moisture for reaction. The crew had two electric injection pumps, one pumping AP Fill 720 with an accelerator and the other pumping water. They had 150-foot lines on each pump. Both pump lines were run through a 100-foot PVC tube. The technicians used a video camera, mounted five feet back from the end of the PVC tube, to monitor the fill. The crew pumped both water and poly in unison for a good reaction. As the pipe filled up, they slowly withdrew the PVC and continued pumping until the pipe was full. The process basically consisted of pumping, extracting the tube a foot, and repeating - until the entire 18" x 100' pipe was filled.

Rapid Result

The deteriorated pipe was completely filled and stabilized. Soil migration was stopped and the threat to the structure of the spillway above was eliminated. This job was completed in only three hours. Complete removal or filling with concrete would have taken days. In addition, concrete does not expand, so a 100% fill would have been impossible. AP Fill 720 expanded to fill 100% of the pipe. The consulting engineer and general contractor were very happy with this result.

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A geotech contactor was called to Livingston, NJ to evaluate a settling man-made waterfall. The waterfall was constructed to continuously pump water from the pond below to the very top, so it could flow back down over the rocks. Over time, leaks and voids began to form through the entirety of the structure due to erosion. The structure itself started to settle as the water began washing out the soil underneath. In order to remediate the problem, the contractor advised undersealing the entire structure to seal it and fill voids underneath. This process would stabilize the entire structure and prevent any further movement.

Powerful Polymer

To complete the job, the contractor selected Alchemy-Spetec's AP Fill 720 structural polymer due to its ability to permeate and encapsulate loose supporting soil into one solid mass. This material is a single component, closed cell, hydrophobic, water-reactive, solvent and phthalate-free, low-viscosity polyurethane injection resin for stabilizing soil and filling voids around structures (cutting off any existing leaks in the process).

Painless Procedure

The crew drilled small holes, installed injection ports, and injected the material into the soil below, every four feet, eventually creating a grid pattern across the entire structure. They started this process at the top of the structure and worked their way to the bottom, injecting the material into each spot until the void was full (a.k.a. grouted to refusal).

Rapid Result

From the start of the project, planning, and evaluation took about a month. Once the injection plan was in place, the crew completed the job in just a day and a half with a four-man crew. The man-made waterfall is now leak free and will continue to see decades of further use. 

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Loose, unstable slabs with voids underneath are often referred to as "rocking" slabs due to their movement when forklifts cross over them. Rocking slabs are a common problem in many warehouses. Left un-repaired, they can cause damage to equipment and injury to workers. Eventually, rocking slabs will require replacement if they are not repaired properly.

Rocking Slabs Can Cause:

• Slab Deterioration Over Time
• Floor Destabilization
• Damage to Material Handling Equipment & Loads
• Trip Hazards & Litigation Risk

How to Repair Rocking Slabs:

1. Inject high-strength, high-density polyurethane foam underneath the slab for lasting support.
2. The polyurethane expands to fill any voids underneath and cures to support 14,000 lbs/square foot.
3. Easily clear excess foam from the surface of the slab.
4. Repaired slabs are traffic ready in just 15 minutes!

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We've created a video for a question we get asked a lot: "How do I make single-component samples?" A lot of people want samples, sales teams love samples, homeowners love them because it’s actually something they can put in their hands on. They can really help close a deal.

The two samples we're going to be making in this video are:

• An AP Fill 700 permeated sand sample. You'll see the permeated sand at the bottom with the foam on top. People like these because they have a nice smooth finish on them, and they demonstrate both the permeation and foaming aspects of the material. They also demonstrate the strength of the material.
• An AP Fill 720 foam sample. These are great for seawall guys, the infrastructure guys, whenever you want to show an HOA or a marina what the pure foam will actually look and feel like.

Watch the demo video now...

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As one of the most impenetrable permeation grouting products on the market, AP Soil 600 is a single component, moisture activated, hydrophobic, low viscosity, polyurethane soil grout. This permeation grout is ideal for stabilizing loose sand and soil around all types of concrete structures, as well as for sinkhole remediation. This post will focus on the specific reasons why AP Soil 600 is your best option for stabilizing sandy soils.

Sandy soils erode easily with any kind of rain event. Once the erosion and soil migration starts, you may start to notice settlement occurring alongside the structure in a variety of ways. Poor compaction and erosion of sandy soils affect all types of commercial buildings, residential homes, driveways, roadways, and more. Typically you may find some kind of cracking or settling in structures as sandy soils begin to erode.

AP Soil 600 is a powerful chemical grout that permeates sandy soils to lock everything in place. Once the grout cures, the sandy soils turn into a solid mass. This grout is so strong that it is often used to solidify soil supporting buildings with large excavation pits right next to them. Grouts such as AP Soil 600 are the only option in some situations in which helical piers, push pile piers, or driven sheet piles cannot be used. AP Soil 600 is also installed in confined space situations where a non-invasive procedure is needed.

Installation is fairly straightforward. Typically injection tubing rods will be driven down to the depth required by the situation, with the rods spaced apart about every 18 inches. A small amount of catalyst is added to AP Soil 600 as it is slowly pumped into the sandy soils underneath. (The ideal pump system for this procedure is Alchemy-Spetec's PolyShark.) A gallon of product is slowly injected into the sandy soils for every foot of depth. Typically a small crew of two or three is all that is needed.

Once injected, the chemical grout will cure within 24 hours, solidifying the sandy soils and fortifying support for the structure's foundation. 

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A general contractor working for a school district in Buffalo, New York was asked to lift and level around 550 feet of sidewalk slabs at a local high school. The general contractor called in slab lifting specialists Gernatt Spray Foam to get the job done. Since sunken slabs often result in trip hazards, getting the job done quickly and permanently was a top priority.

Powerful Polymer

The slab lifting crew showed up on the scene armed with AP Lift 435 high-strength polyurethane and several Jack Attack devices.

Painless Procedure

Gernatt Spray Foam leveled all 550 feet of sunken sidewalk slabs with total precision. They performed lifts ranging from 0.5 to 6 inches, depending on the slab. In some cases, they lifted with polyurethane only and in others, they raised the slab with the jacking devices before injecting the polyurethane underneath.

Rapid Result

The entire job was completed in only two days. The general contractor and school administrators were both amazed at the efficiency and surgical precision of the polyurethane slab lifting method.

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It's not an exaggeration to say that that the PolyShark® soil stabilization and seawall repair pump system is unmatched in the marketplace. What makes it so unique?

A Geotech Pump System Like No Other

The PolyShark® system includes injection hoses, suction lines, flow meters, a custom solid steel frame, a skid-mounted setup, and top-of-the-line components. It is a complete turnkey unit, ready to go upon arrival. Let's take a closer look...

• Two 350 feet injection hose reels are included, allowing an exceptional amount of additional reach for limited access and/or remote location jobs.
• Suction lines make it easy to pump material from totes, drums, or even pails if needed. This type of flexibility is not common to all geotech pumps.
• Flow meters make it easy to accurately track the amount of material pumped.
• The custom solid steel frame, polyurea coated for excellent chemical resistance, is built to last and weather all types of environments.
• The skid-mounted setup keeps all system components together, allowing for easy transfer from truck to trailer to the ground on a job site if necessary.
• The Honda gas motor, Titan hydraulic pump, and Titan hydraulic fluid ram are top-of-the-line, tried, and true components. This means less maintenance and downtime when compared to competing systems.

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Alchemy-Spetec's AP Fill 700 and AP Fill 720 are one-component polyurethanes used for filling voids in supporting soil surrounding a structure.  Situations in which these materials might be used for void fill include soil adjacent to retaining walls, basement walls, seawalls, and infrastructure boxes.  

Benefits of One-Component Void Fill Foams

• Their slow reaction time allows for the material to travel farther from the injection point, fill more voids, and permeate more soil before curing.
• They're ideal for encapsulating underground debris (decaying organics, roots, buried construction waste).
• On small jobs, they can be installed with a very small, portable pump that can be lifted and transported by hand. 

Differences Between AP Fill 700 and AP Fill 720

• AP Fill 700 features very low viscosity, making it ideal for permeating fine soil with small voids.
• AP Fill 720 is extremely rugged and durable when cured, while still retaining some flexibility. Its high expansion rate makes it ideal for filling larger voids.

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