Nick Carriere
Not every concrete lifting foam is the same! When choosing the right solution for your application, you must consider various factors to ensure project success and maximize your potential for earning future jobs.
Understanding the Important Characteristics of Concrete Lifting Foams
There are special characteristics you need to look for when deciding what polyurethane foam to use for lifting and leveling concrete. Expansion is important, but what about set up and cure times or adhesion?
Foam Reaction Time
Foam reaction time for concrete lifting is an important property to consider when choosing the best polyurethane foam for the job. Too quick a reaction time can create foam pillars under the slab, leaving a large percentage of the slab unsupported and making the contractor more susceptible to a callback due to resettling, or even worse, the slab cracks from being voided when the weight of a vehicle is on it.
Too slow a reaction time can lead to the foam escaping outside of the slab being raised and possibly underneath an adjacent slab, leading to a lift on an unintended slab.
It’s also important to consider the project that will be completed. Is it a sidewalk project with small slabs that will require a foam that sets up fast enough to not escape beyond the slab? Or is it a large roadway panel where a slow reaction time is ideal to let the foam spread and fill as much void underneath as possible while minimizing the need for numerous holes? The proper reaction time in the polyurethane foam being used is crucial to maximize efficiency and success.
Foam Adhesion
Polyurethane foam for concrete raising should lift the concrete without sticking to it. This is why it is important to have a foam that skins over quickly, preventing it from sticking to the slab or the surroundings.
For example, if raising a slab along a concrete foundation without a foam that forms that tough exterior skin quickly, the foam will stick to the slab and the foundation, effectively locking that slab into place.
A foam that skins over quickly will not adhere to the foundation wall and will allow that slab to rise freely. This eliminates the need for repeated saw cutting to free the slab, saving the contractor valuable time.
Foam Density
In concrete raising, the foam’s density is selected based on the slab weight, meaning heavier structures like foundations and roadways require higher-density foams, while lighter applications require lighter foam densities.
HMI offers a variety of concrete raising foams in different densities and reaction times. While these varying foams have their own ideal uses, there is a great amount of crossover between them, allowing you to tackle a wide variety of projects without having to carry multiple densities of material.
Our Foams and Their Uses
Our 2 lb. per cubic foot foam is our quickest-reacting foam and also has the lightest density. This makes it ideal for manipulating smaller slabs such as sidewalks and driveways, while also providing the highest yield.
Our 4 lb. per cubic foot foam has a higher density and slower reaction time than the 2 lb. foam. This is often used on projects with heavier lifts, such as roadways and warehouse floors.
We also offer a Fast version of the 4 lb. foam, which provides you with the density of the 4 lb. foam with a reaction time very similar to the 2 lb. foam. This gives our customers the ability to raise everything from sidewalk slabs to roadway panels without having to change foams, making it our most popular selling foam!
Our 6 lb. per cubic foot foam with a slow reaction time is designed to raise heavy highway panels and withstand heavy truck traffic. It spreads well under the large slabs since its slow reaction time gives it time to fill the space and provide support.
How Foam Density Works
The density of the foam is determined by the amount of material required to fill a one cubic foot box at free rise, without any compressive force upon it. Therefore, one can see the variance in yield of these foams as 6 lbs. of our highest density foam is required to fill the same space as 2 lbs. of our lowest density foam.
However, on a typical concrete raising project, the foam is being pumped into a confined space with the force of the concrete pushing down on it. This pressure allows more of the material to be pumped into the same space, thus increasing its density to what is required to raise and support the slab.
An Example of Increasing Density
Imagine you have a one cubic foot box with a weighted lid. You inject 2 lbs. of a 2 lb. per cubic foot foam, which completely fills the box. Now, if you inject another pound of foam, one of two things will happen:
- The foam will expand to lift the lid
- The foam will build upon the existing density, increasing it to 3 lbs. per cubic foot.
This example describes how a 2 lb. foam can lift much larger and heavier slabs than the sidewalk slabs it may be designed for. The trade-off is that as you increase the foam density, you sacrifice the high yield of the 2 lb. foam. This principle goes to show why the varying foams are designed with specific uses in mind, but also provide for a large amount of crossover.
Foam Pliability
The ideal polyurethane foam for concrete raising does not fully cure immediately. This gives the foam pliability until it is fully cured, allowing the contractor to continue manipulating slabs into place after the foam has fully expanded. Concrete lifting contractors know that by raising one corner of a slab, the opposite corner can be brought down if there is a void underneath that corner or if the foam is still pliable.
This allows for better fine-tuning of the concrete for the best end result. The ideal foam will stay pliable after fully expanding for approximately 15 minutes. This allows for continued manipulation but still cures fast enough so that by the time the contractor leaves the jobsite, the foam is fully cured and the concrete is available for full use.
New Trends in Polyurethane Concrete Lifting Foam
New trends in expanding polyurethane foam for concrete focus on making the process more efficient, environmentally friendly and precise.
Renewable Foams for a Lower Carbon Footprint
This advancement supports sustainable practices with polyurethane foams made of renewable materials. By shifting to these foams, you can reduce the carbon footprint of concrete repair and minimize your environmental impact.
At HMI, our eco-friendly polyurethane foams use over 40% recycled materials that meet USDA Certified Biobased Product approvals.
Advanced Polyurethane Equipment for Improved Precision
The concrete lifting industry is experiencing significant transformation with the introduction of advanced rigs. These integrated systems offer greater control and efficiency during concrete lifting due to different features:
- Precise injection: Advanced polyurethane equipment uses air purge which keeps the injection port open so contractors can work methodically, avoid over-lifting, and easily return to previous sites. The result is a controlled lift and consistently high-quality work without drilling extra holes.
- Real-time monitoring: You can monitor pumping pressure in real time, helping you use the correct pressure for a successful lift.
- Ergonomic design: Equipped with an easy-to-use rolling handle, advanced tools minimize fatigue while allowing you to seamlessly switch between air and material flow for improved job efficiency.
Invest in quality engineering with the EliteONE Injection Foam Gun and increase work precision and efficiency.
Polyurethane Foam for Concrete Repair: Beyond Concrete Lifting
Polyurethane foam is a versatile material suitable for more applications beyond lifting concrete slabs, including:
Filling Voids
Expanding polyurethane foam offers a fast and minimally invasive way to fill voids resulting from soil erosion, buried organic material decay and settlement. The lightweight foam restores concrete slab support without adding considerable stress to the underlying soil. Its waterproof nature also prevents future erosion.
Stabilizing the Soil
Through deep injection, polyurethane foam addresses poorly compacted soil. It creates a strong, stable foundation to support the concrete long term.
Water Control
Polyurethane foam can flow into cracks and joints, closing off some water pathways and reducing infiltration. In certain cases, contractors see a noticeable reduction in water movement.
Choose HMI for High-Performance Polyurethane Foam
At HMI, we offer various high-performance polyurethane foams to meet your specific application needs. We also sell different high-quality polyurethane concrete raising equipment to support your projects.
In addition to quality foams and equipment, HMI stands apart with responsive customer support, financing and hands-on training for your crew. Call 888-793-9484 today to get started with our products. You can also submit our online form.
