About Acme Concrete Raising & Repair
Acme Concrete Raising & Repair (Acme) is Chicagoland’s original polyurethane injection specialist. Utilizing various polyurethanes, we raise and stabilize concrete and address complex problems in subsurface geology. Known for advanced solutions and using the highest-quality specialized materials and equipment, we’re the go-to company for engineering firms, commercial property owners, HOA’s, and municipalities all across chicagoland.
Mudjacking Overview
For decades, mudjacking has been relied on as an easier alternative to the mechanical means of raising settled concrete slabs and structures. Although only a temporary solution, mudjacking is relatively cheap and can be performed relatively quickly using simple, abundantly available materials such as clay, soil, sand, and water. Without the need for any complex or specialized equipment, contractors can easily provide these services with minimal investment or training. Generally, a small dump truck with a mixer and mud pump is all that’s needed to gear up to provide mudjacking services. Understandably, contractors love being able to use cheap and easily obtainable materials; however, property owners pay the price in the long run. In short, there are many factors involved when raising concrete that determine the appearance and longevity of a repair. With the availability of current technology, the shortfalls of mudjacking have become abundantly apparent. Ultimately, the cause of the most fatal flaws of mudjacking technology is found in the physical characteristics of the material itself.
Polyurethane Overview
Polyurethane foams were initially developed for concrete raising and stabilization in the 1980’s. The polyurethane concrete raising process was designed and patented specifically for use in large infrastructure repair projects. A common application was and still is the raising of roadways settled at bridges, causing uneven driving surfaces. Since the development of these initial foams, patents have expired, and the technology has been adapted to meet the needs of residential and commercial applications.
Physical Characteristics of Concrete Lifting Materials
To provide consistently reliable repairs to settled concrete, lifting materials need to possess critically important characteristics. Understandably, lifting materials should be stronger than the needs of an application, as well as have the ability to resist any impacts posed by their surrounding environment.
Material Spread
One of the most important things a lifting material needs to do is provide a uniform support structure. For this to occur, a sufficient amount of material needs to be used that also adequately travels or spreads beneath the slab when injected.
Mudjacking Spread
No matter how a contractor describes it, mudjacking is a high-viscosity (thick) and extremely heavy soil/aggregate based slurry. The high-viscosity of the material is needed in order for it to be able to lift the slab. A low viscosity material would simply spread out and not provide any lifting power. Since the material has to be thick to provide lift, many holes have to be drilled to properly fill the areas beneath the lifted slab. Alternatively, without a sufficient quantity of holes, mudjacked slabs are not properly supported.
Polyurethane Spread
Polyurethane is a very low-viscosity (thin) material, something similar to olive oil, which travels very easily when compared to thick mudjacking muds. Acme injects polyurethane with special air-purged injection equipment at approximately 1,400 pounds per square inch. This material spreads rapidly in all directions while expanding and pushing into voids. The air-purging component of our equipment keeps passageways open and clear for subsequent injections, further promoting material spread beneath the slabs. The result is a slab that’s not only lifted but is indeed properly supported.
Compressive Strength
Compressive strength is a topic most people are not familiar with and have no point of reference to know what a good rating is versus a bad one. In simple terms, when discussing lifting materials such as mudjacking mud or polyurethane, compressive strength represents the lifting material’s ability to withstand loads before failure. These loads are numerical values typically expressed in pounds per square inch (psi). Naturally, concrete slabs and structures are very heavy and designed to carry loads that are even heavier than the slab itself. When raising concrete, the material used must be capable of withstanding the weight of the slab along with anything that may be on the concrete, plus some margin of error. In short, lifting materials should be stronger than the application would ever require.
Mudjacking Strength
Each mudjacking company creates its own mudjacking slurry based on the materials and procedures of their choosing. In short, there is no consistency between contractors, some mudjackers claim to add cement to their mix, while others do not. It is impossible to describe the actual compressive strength of mudjacking material with such variation across the industry. All we can rely on is our own personal experience, which includes raising a lot of concrete that had been previously mudjacked. In all cases, the mudjacking material we’ve come in contact with does not contain any binding agent at all. This includes concrete that was raised with material described as any of the following: cement, mortar, custom mortar mixture, type S mortar, and clay with sand and cement.
We regularly obtain samples of these materials to conduct very basic testing. Typically, we remoisturize samples of the material, form cubes, and allow it to fully dry. Once cured, we find that only light physical pressure is required before the cubes are easily crushed. Our findings are that mudjacking material only produces minimal compressive strength, likely in the 10 – 20 psi range.
Polyurethane Foam Strength
Polyurethane foams are formulated to meet specific compressive strength requirements. These foams are typically designated for a particular application, such as residential, commercial, or municipal. When properly applied, polyurethane foams will provide a support material with a compressive strength rating far exceeding any load the slab would ever encounter during normal usage.
Take the Illinois Tollway, for example. In their publication, “Illinois Tollway Guidelines for Pavement Assets,” we refer to Section 2.4.2 Slab Jacking, Special, which states:
The material used for raising the concrete slabs shall be high density polyurethane slurry exhibiting the following characteristics: Compressive Strength (KPA) ASTM D 1621 (at Yield) ……………………………… 324
The compressive strength rating for raising sections of the tollway is stated to be 324 kilopascals, or about 47 PSI. Our standard, general purpose polyurethane has a 90 PSI rating, far exceeding what’s required to raise highways. However, this rating may sound low or unimpressive to someone not familiar with material physical properties, so let’s put this into better perspective. It’s important to realize that these compressive strength ratings are given in pounds per square inch.
Take, for example, a square slab of concrete that’s 10 feet wide by 10 feet long. Imagine this slab is supported by a 1-inch thick layer of polyurethane foam with a 90 PSI compressive strength rating. The slab, being 10 x 10, would consist of 100 square feet. However, each square foot contains 144 square inches. This means the surface area of the slab consists of 14,400 square inches. When we multiply 14,400 square inches by a 90 pound per square inch compressive strength rating, we end up with a weight rating of 1,296,000 pounds!
FUN FACT: POLYUETHANE IS REQUIRED FOR TOLLWAY REPAIRS; MUDJACKING IS NOT EVEN CONSIDERED.
The Illinois Tollway Authority provides clear evidence of the shift away from mudjacking and on to advanced polyurethane systems. For many years, various Departments of Transportation (D.O.T.) across the nation relied on mudjacking to raise sunken concrete roadways. Monitoring these repairs over time revealed the inherent temporary nature of mudjacking material as the lifted roadways invariably resettled. D.O.T. reports have thoroughly documented the fact that mudjacking materials are susceptible to moisture and erosion. Today, for example, the Illinois Tollway does not allow the use of any type of mudjacking material and requires polyurethane for raising & stabilizing its roadways.
Durability of Concrete Lifting Materials
Since the majority of raising & stabilization applications involve exterior concrete, lifting materials must resist the impact of environmental conditions. The durability of lifting materials has a significant direct impact on how long a repair will last. In the Chicago area, we regularly encounter deep freezes, droughts, and flooding. As far as concrete raising is concerned, the most damaging of these, without exception, is moisture in the form of rain, improper drainage, flooding, or plumbing leaks.
Mudjacking Material Durability
Mudjacking slurries will harden in dry conditions; however, in outdoor applications, exposure to moisture makes them very susceptible to failure. As mudjacking materials reabsorb moisture, they lose strength and allow the concrete to sink again. In worse conditions, water intrusion can actually cause the mudjacking mud to wash out from beneath the concrete. As these situations take place, the raised slab loses support and may crack under its own weight and require replacement.
Polyurethane Foam Durability
Polyurethane is essentially permanent and lasts decades; it isn’t affected by water or extreme temperature fluctuations. It’s also not affected microbially or by insects or rodents. The only environmental conditions a negative impact are U.V. rays. However, being installed sub-surface, U.V. rays have no way of contacting the material.
Weight of Concrete Lifting Materials
Weight plays a big role when it comes to settled concrete. It’s a fact: concrete would not sink so badly if it wasn’t so heavy! With this simple analysis, it’s not hard to come to the conclusion that lifting materials shouldn’t be heavy. It does no good to add significant weight to an area already prone to settlement problems.
Mudjacking Mud Weight
Weight is another flaw of mudjacking technology. No matter what exact “mix” a mudjacker employs, these slurries will weigh somewhere between 100 and 150 pounds per cubic foot. On the surface, this may not strike someone as being a problem. To put this into better context, consider the scenario where a mudjacker raises a patio that requires 1.5 cubic yards of mudjacking material; a minimum of 2-tons of weight will be added! Adding 2 tons of weight to an area with a history of sinking can, in itself, be the cause of future settlement.
Polyurethane Foam Weight
Most polyurethane foams used in the raising and stabilization industry weigh in the 2 to 4 pound per cubic foot range. In the example given above, if we raise a patio requiring 1.5 cubic yards of material, we’re adding less than 200 pounds to the area. The weight added by the polyurethane material is relatively insignificant.
Aesthetics of Raised Concrete
Concrete repairs should not negatively impact the visual appearance of your concrete. A quality repair should address the problem while leaving your concrete looking great! When considering a repair, dig deep into the process being proposed and be sure you have an accurate understanding of how your concrete will look once it’s raised.
The Visual Impact of Mudjacking
A major downside to applying this method, particularly in the residential & commercial markets, was the injection hole size. The mudjacking process required many large (1.5” – 2.0” dia) holes to be drilled into the slab. After patching, these large holes would permanently scar slabs and degrade the aesthetics & value of the property. Many times, years later, these large patches would fail, resulting in dangerous trip hazards. Unfortunately, most any concrete raising or stabilization project will involve drilling holes in the concrete, which, in some cases, can negatively impact its visual appearance.
Mudjacking hole patches can visually stand out to the point where some property owners regret having had the service performed.
The Visual Impact of Polyurethane Foam Concrete Raising
With our current technology, these horror stories are a thing of the past. The great spreading characteristics of polyurethane, combined with our air-purged injectors, allow us to properly support slabs with fewer holes compared to mudjacking. This, combined with the very small injection hole size of 5/8 -inch, means your concrete is minimally affected by the repair process, leaving you with raised, stabilized concrete that still looks great!
Concrete Raising Warranties
You should get a solid warranty when paying to have concrete raised.
Keep in mind that when a contractor bids on your project, they’re employing sales tactics. For some contractors, it’s a boisterous claim of providing the best solution on the planet, while others rely on the soft sell – relying on track record, facts, and technological advantage. Either way, as they say, talk can be cheap. We recommend referring to what’s in writing. If someone tells you that if you hire them, your concrete will last 20 years or more but only states a 1-year warranty on the estimate, you should take a pause.
Also, when evaluating warranties, don’t just refer to their duration; you must read the fine print. A classic tactic of service companies is to have a great sounding warranty with fine print drastically limiting its actual value to the customer. Imagine thinking you are covered by an 8-year warranty only to have the contractor not honor the warranty because you failed to meet some conditions in the fine print.
Mudjacking Warranties
Due to the temporary nature of mudjacking, contractors typically offered warranties that only lasted between 1 and 2 years. There are exceptions to this where contractors offer longer durations, but those warranties also commonly contain restrictions that would significantly limit the contractor’s ultimate responsibility, where warranty claims would not be honored.
Polyurethane Warranties
From a consumer’s perspective, the written warranty that the contractor offers is the most crucial factor in terms of practical durability. When having your concrete lifted with polyurethane, you should expect a warranty in the 5–10 year range. However, like some mudjacking warranties, there are also polyurethane contractors offering warranties that contain limitations or restrictions that greatly limit their responsibility. Always read the fine print!
Application Specific Lifting Materials
Not all concrete settlement issues are created equally! Some issues are deep below the bottom surface of the concrete, while other situations involve only filling voids and providing adequate support. No matter what the circumstances are, it’s important to utilize a material consisting of properties that meet the specific needs of the problem. In our industry, we have to rely on a variety of materials to best remedy any particular problem.
Mudjacking Material Variations
The final flaw of mudjacking we’ll discuss is its lack of ability to address complex problems. Mudjacking is typically not able to be deep injected in order to remedy subsurface problems, and is also not able to be used in wet locations. In most cases, the variability of a mudjacking slurry is limited to its initial moisture content. Some contractors may add cement or adjust cement content, but this is rare, as most mudjackers do not use cement in their mix. Utilizing higher moisture levels allows the material to spread more beneath the surface, while dryer materials tend to lift more than spread. In any case, mudjacking is severely limited in its ability to adapt to more difficult, complex problems that are commonly encountered.
Polyurethane Lifting Materials
Specialty polyurethane materials provide ideal physical and chemical characteristics for dealing with a wide range of problems. Our dual component products excel at raising, stabilizing concrete, and strengthening subsurface soils. Other single component formulations are specially designed for sealing penetrations and gaps along and beneath seawalls and municipal infrastructure. With our wide array of materials and specialty equipment, we have the ability to solve simple, common residential and commercial issues, all the way to the most complex industrial and municipal problems involving critical infrastructure.
However, the real benefit of polyurethane is the physical characteristics of the material itself. Our polyurethane is completely water-resistant. In fact, we’re able to raise slabs completely submerged in water with hydrophilic polyurethanes that easily form under water.
Also, unlike mudjacking, our materials cure almost immediately. When we finish raising a driveway, you can drive on it right away!
Wait! There's Much More to Consider When Choosing Between Mudjacking and Polyurethane Foam Concrete Lifting!
When needing concrete raised or stabilized, polyurethane should be an easy choice, but it’s not quite that simple. There is another very critical aspect to consider: EXPERTISE.
Your concrete is an important and expensive feature of your property. The fact is, working with polyurethane is not as straightforward as one might assume. We see the failed attempts regularly: cracked slabs, overlifted slabs, slabs not level, slabs not raised high enough, joints uneven, and trip hazards that remain. Even when the initial goals “appear” to have been met, non-specialist companies are notorious for failing to properly support lifted concrete, which results in re-settlement and possible cracking.
Buyer Beware!
Today’s marketplace includes large supply companies selling polyurethane material, equipment, and marketing materials to businesses that are anything but specialists in this field. We refer to these non-specialist businesses as “multi-service” or “multi-purpose” companies. These companies typically provide a number of other services, such as installing epoxy concrete coatings, waterproofing, power washing, or spray foam insulation. Looking to increase sales by adding another service to their list of offerings, these companies put consumers’ concrete at risk every single day. This flawed service offering typically begins as they send a salesperson to evaluate your project. We know from experience that the only way to accurately evaluate and properly plan a lifting or stabilization project is to utilize a highly trained and experienced field technician. Only a well-seasoned technician who has personally injected polyurethane at hundreds, if not thousands, of project locations can foresee what’s required to achieve the best possible outcome for the owner.
Generic Equipment
Another telltale sign of these non-specialist type companies is the injection equipment being used. Many equipment manufacturers & suppliers offer these multi-service companies mechanically purged injectors that are simple, easy to use, and easy to maintain. Unfortunately for you, the customer, these simple injectors do not actively promote material spread beneath the slab. Mechanically purged injectors simply “stacks” polyurethane on top of itself, resulting in what we refer to as “piering”. Piering does not result in properly supported concrete and can be a contributor to re-settlement.
Generic Materials
Multi-service companies that offer concrete raising are typically “one-material, one-process” type service providers. However, concrete raising and stabilization projects are not that simple. Site conditions can vary greatly from one project to another and benefit from a wide array of materials and techniques. Polyurethanes are developed with unique characteristics and require the expertise of highly trained technicians to properly apply the right material for a given set of specific project conditions. Not only is it crucial to choose the correct type of polyurethane, but a specialist is also needed to utilize the right equipment and apply the proper injection technique.
Lack of Focus
Behind the scenes, multi-purpose companies spend time and resources to talk about, prepare for, and conduct operations pertaining to services other than polyurethane injections. While it’s true they likely spend some time focused on polyurethane, it’s certainly not their primary task at hand. This is an absolute fatal flaw when it comes to providing quality services. Quality concrete-raising services will not tolerate anything less than 100% focus and dedication. We know the only way for us to remain the best is to keep devoting our entire business and operations to raising concrete with polyurethane.
Acme Concrete Raising & Repair is a true polyurethane specialist and only utilizes specialty injectors equipped with compressed air purging. Air purging creates and maintains passageways beneath the slab for the polyurethane to spread out and better support the slab. These specialty injectors add some complexity to our systems, however, it’s a small price to pay for better material flow.
Your concrete is too important to trust with anyone other than a true specialist—a company that only focuses on one thing: polyurethane concrete raising & stabilization!
