Category Archives: Void Detection
GPR, or Ground Penetrating Radar, is a convenient and effective way to see what is going on underneath a concrete slab. In the past, if someone wanted to inspect underneath a concrete slab, they would have to either drill holes in it or break up the slab. Imaging technology has progressed over the years to provide a clearer look, without damaging the concrete.
A benefit of the improved technology is that it is now easier to see what is underneath the concrete. This information will help prevent damage to utilities and equipment and harm to employees and other people. Damaging pipes, cables, wires, and other structural objects can cost you money and time, in addition to being dangerous. By imaging conduits, structural supports, and reinforcements ahead of time, you minimize the chances of damage occurring.
Early Tech Used X-rays
One of the first methods of imaging beneath the concrete was through the use of X-ray machines. Unfortunately, there were a lot of drawbacks to using X-rays. There needed to be a film on the opposite side of the area being scanned, which could be difficult, if not impossible. Additionally, people would need to be evacuated due to radiation concerns. Depending on the type of structure, the number of people, the location, and other variables, this could be a very involved process.
If these issues were overcome, you would still have to wait while the images were processed off-site, then interpreted. This could take days to complete. While the images were good for seeing materials like rebar, it was not a simple process.
GPR is the Tech of Today
Although X-rays and other methods are still used today, GPR is the best method available. Solving some of the issues that occur with these older methods, GPR is becoming increasingly popular. GPR systems don’t require film, doesn’t emit dangerous radiation, and the data can be accessed immediately. There are options that GPR can use that aren’t available to other types of tech. Different frequencies can be used to identify different depths and along with 3D imaging, GPR can also display visuals in 2D and 1D. This can be useful in viewing congested areas.
So how does GPR work, exactly? The basics of a Ground Penetrating Radar system is the utilization of an antenna that produces an electromagnetic radio wave. This radio wave travels through concrete, soil, and other materials until the wave “hits” something, creating a discontinuity in the wave. When the wave encounters a disruption, some of the wave is reflected off the object and travels back to the antenna.
When the radio wave energy returns to the GPR unit, the two-way travel time and the amplitude is recorded. The travel time will determine the depth of the object and the amplitude shows how different the object was compared to the surrounding material. More energy is reflected the more there is a difference between the two materials. A trained GPR engineer can analyze this data and determine if the object is rebar, PVC, cable, or something else.
To scan a concrete surface, the GPR unit is placed on the surface and pushed along the concrete. This will produce a 2D image of what lies beneath. When several images are collected, they can be used to create a “depth map” or “time slice”. These collected images can show embedded objects at varying depths. The machines take the detailed scans, but it takes a highly-trained technician to interpret the data.
Concrete Construction and GPR
The accuracy of the GPR scans and the skills of the technician lends itself to concrete construction issues. By being able to precisely locate things like rebar, conduits, tension cables, and other objects, the contractor can avoid accidents while cutting or drilling into the concrete. The technician will be able to let the contractor not only know that there is something in the concrete but where it is and what it is made of.
Another use of GPR in relation to concrete is to determine the thickness of the slab. The radio wave that is emitted by the unit not only can detect objects, but it can determine when the concrete ends and the soil begins. Contractors can use this data to assess the deterioration of the concrete and the structural capacity of the slab. Older methods might have only covered one section of the concrete, but the GPR can cover large areas.
GPR is extremely useful when it comes to identifying cracks and voids beneath the concrete surface. It is vital that these problem areas are identified and repaired. A skilled GPR technician will be able to analyze the data and identify these defects.
Find a Skilled GPR Operator
Just about anyone can buy a GPR unit, but it takes skill and expertise to effectively use the machine. The tasks that the GPR unit can do range from the fairly basic job of locating and marking obstacles to void and crack detection. Make sure that the GPR technician you hire can complete the job you need. An operator with basic knowledge can determine the difference between steel and concrete, but you will want to hire someone with more training and experience if you need to complete more complicated tasks.
If you have any questions regarding GPR, please feel free to contact the experts at Polyjacking.com and Pro Foundation Technology. We will be happy to answer any questions you may have and help you effectively use GPR on your next project.
The professionals at Polyjacking.com were recently called in to help with some floor leveling repairs that were needed on the campus of KU Edwards in Overland Park, KS. The campus was opened in 1993 and offers programs for undergraduates, graduates, and certificates along with professional and continuing education courses.
Floor Leveling and Void Filling on KU Edwards Campus
We were called in to take a look at an unlevel floor in one of the on-campus buildings. Upon inspection, we discovered that the floor needed to be raised by an inch due to voids that had formed under the building that had caused the floor to sink. The voids were around five feet below the surface and caused by a broken water line. Our experts leveled the floor and filled the voids, providing a stable foundation for the building and a safe environment for students and faculty members.
Please view the gallery below with some pictures from the work site. If you have any questions or would like more information, please contact us at Polyjacking.com.
When the ground under a concrete slab erodes, it can cause a lot of problems. Homes with basements usually have the most problems, but voids can impact driveways, patios, sidewalks, and more. The erosion causes air pockets or voids to develop under the concrete slab, taking support away from the surface.
Causes of Voids
There are several different reasons that a void can occur beneath your concrete. Most of the time, it isn’t due to erosion, but other factors. Some issues can happen quickly, while others can take years to cause problems.
Soil consolidation occurs over time. This occurs when loose soil under the concrete consolidates or sifts down. If the soil is not properly prepared by being tamped down, this can occur. When the soil consolidates, a void can form over time.
Settlement is a natural occurrence that happens over time. It can occur with new construction or with a property that is a hundred years old. It all depends on the type of soil and weather patterns. Heavy rains or flooding can cause the soil to settle faster than normal. If the settling soil is in a large enough area, it can allow erosion to occur. Settling soil sets the table for a problem, erosion just makes it worse.
If water doesn’t drain correctly or there is new landscaping or other additions to the property, erosion can start after years with no problems. The water will run freely, washing out the soil and creating a void under the concrete. The bigger the void, the more damage that can occur.
Solutions for Voids Under Your Concrete
You don’t have to tear up your concrete to fix the problem of having a void. The best solution is polyjacking. High-Density polyurethane foam is injected through small holes into the voids. The foam expands, filling the void and sealing any cracks on the underside of the slab. The foam will not wash away and the slab is usable shortly after the foam is injected. Mudjacking is an alternative, but the sand-based grout can be washed away or not fill the void and you’re back to square one.
You’ll still need to take care of drainage problems, as they will continue to cause problems for your home or business. Make sure that water is draining correctly and away from the foundation or concrete area. The polyurethane foam won’t wash away, but the surrounding soil can erode. Let a company like Pro Foundation Technology assist you with waterproofing services.
Protect your property from foundation damage, trip and fall hazards, and sunken concrete by making sure the water is draining from your property. If you already have problems, let an expert like those at Polyjacking.com help you restore your concrete slab to the necessary height.
Historic Building Foundations
Reasons for Foundation Failure in Historic Buildings
Historic buildings, like all structures, often develop problems with a foundation that is sinking or become unleveled over time. There is some special consideration to keep in mind in restoring historic building foundations. Older buildings are particularly prone to foundation failure for several reasons.
Unstable soils – After a period of time, soils beneath and surrounding a foundation may become more compacted, shift, or develop gaps. This may be caused by flooding, removal or addition of trees and landscaping features, or years of changing soil moisture and freezing/thawing patterns.
Improper water drainage – At times, historic buildings are built on old creek beds or new floodplains. Construction on adjacent properties or parking lots may have altered the flow of water toward the property. Over time, even weather patterns may require the installation of improved interior and exterior water drainage systems to prevent foundation damage.
Foundation materials – Many older foundations are built from bricks or stones with mortar that deteriorates over time or develops cracks allowing water to leak and damage the foundation.
Dirt floors – Often older foundations have dirt floors that are more likely to allow water to enter the basement and cause further damage to the foundation.
Signs of Foundation Failure at a Historic Property
Historic properties, like all buildings, often display classic signs of foundation failure:
- Collapsed masonry walls
- Sloping floors
- Cracks in walls, floors, or ceilings
- Misaligned doors and windows
Because historic buildings may be somewhat fragile and have historical value, you must hire a foundation contractor with an established record working on historic buildings.
Overall Guidelines for Restoring a Historic Building
Whenever a historic building requires restoration, there are certain standards which must be followed:
- Retain Original Function – The property must be used in its original function or be given a new use which reflects its original period.
- Retain Original Design and Features – Materials, features, spaces, and spatial relationships from the property’s period will be kept and preserved.
- Retain Original Appearance – Work to stabilize and conserve the property will be physically and visually compatible with the restoration period and documented for future research.
- Use Original Materials – Materials, features, and finishes characteristic from other historical periods will be documented before their alteration or removal.
- Use Original Craftsmanship – Distinctive materials, features, finishes, construction techniques, and craftsmanship of the restoration period will be preserved.
- Repair, Don’t Replace – Deteriorated features from the restoration period will be repaired rather than replaced. If a feature is replaced, it will match the old in design, color, texture, and, when possible, materials.
- Document Changes – Replacement of missing features will be documented to preserve the original history of the property.
- Prevent Damage to Materials – Chemical or physical treatments will be implemented in the gentlest means possible to prevent damage to historic materials.
- Protect Archeological Resources – Archeological resources affected by a project will be protected and preserved in place with as little change as possible.
- Protect Original Design – Designs that were never implemented during the restoration period will not be constructed.
Considerations When Restoring a Historic Foundation
Below are some of the key steps you should undertake when hiring a contractor to repair or replace the foundation on your historic structure.
Hire a Structural Engineer – It’s always a good idea to hire a structural engineer who specializes in historic building foundations or has some experience with historic structures to determine how much of your foundation needs to be replaced. A structural engineer will determine the underlying issues and the best solution to repair the foundation and resolve the problem.
Document the Details – Before doing foundation repair or any restoration on a historic building, it is important to document as many details as possible. Take pictures, do measurements, and write down details of everything you observe. This will ensure that the new foundation will look exactly like the old one.
Hire an Experience Foundation Contractor – Especially with a historic property, it is essential to hire an experienced foundation contractor to restore the foundation. They will know and follow the restoration guidelines and will make certain that you have the necessary insurance and permit. Because of their experience, they will know historic materials and techniques and take extra precautions so that none of the structure collapses or experiences further damage. Polyjacking.com has been a family-owned and operated business since 1978 and has an outstanding reputation in restoring foundations of both residential and commercial structures, including historic ones.
Choose Matching Materials – Often older structures will have a brick or stone foundation, so you want to salvage as many of the original bricks or stones as possible. Even if you replace the original foundation with a concrete one, you can do masonry on the outside to make the new foundation look like the original.
Waterproof the New Basement – As long as you are replacing the foundation, you might want a contractor to place drainage tiles along the perimeter of the foundation to waterproof the basement. Polyjacking.com’s parent company, Pro Foundation Technology does basement waterproofing.
Consider Related Projects – If you have an old staircase in the basement that cannot be used, hire someone to build a new one. It’s also a good time to check and replace any outdated electrical, plumbing, or drainage systems. Replacing the soil around the foundation with a quality black topsoil and grading it to a five-degree angle away from the foundation will provide good exterior drainage.
Why Polyjacking.com is Best for Historic Foundations
There are several compelling reasons why Polyjacking.com would be the first choice to lift, level, and restore a historic foundation:
- Professional Experience – Polyjacking.com has professional experience lifting and leveling historic building foundations, including the historic Memorial Union at the University of Missouri and the 200-year-old Belle Meade Mansion in Nashville, TN.
- Ground Penetrating Radar – Polyjacking.com uses ground penetrating radar (GPR) to detect holes and voids beneath historic foundations.
- Hole and Void Repair – The polyjacking process fills in holes and voids beneath historic foundations, providing a strong and long-lasting solution without doing any excavation.
- Quality Products – Polyjacking.com uses only the finest tools and equipment from Earth Contact Products (ECP), the leading American manufacturer of foundation repair products.
- Quality Service – Polyjacking.com has been awarded for super service by Angie’s List.
Contact Polyjacking.com Today!
The professionals at Polyjacking.com are experienced at lifting and leveling historic structures. We appreciate the extra considerations it takes with working on a historic site and we make the extra effort to preserve and protect the structure’s integrity. Whether you have a historic structure or are making history with a newer one, contact us today.
With its beautiful Gothic architecture and bell tower, the Memorial Union at the University of Missouri has unfortunately been slowly deteriorating. This iconic building was built to honor the 117 Mizzou alumni who died in WWI. Due to soil erosion and severe dry conditions, voids, and cavities formed beneath the surface. In turn, this caused the concrete slab to become uneven, becoming a significant threat to everything in its path.
Determining a Solution for Memorial Union
A team of engineers, with structural design and environmental engineering experience, inspected the damage. They came to the conclusion that polyurethane foam would be more effective as opposed to using mudjacking. NCFI’s TerraThane Geotech foam system, the best in the spray foam industry, was used to repair the settlement. The area consisted of 1,200 sq. ft under the offices of the buildings and 1,500 lbs of TerraThane was injected into the surface. Unlike mudjacking, which uses holes around 2-3″ in diameter, 5/8 inch holes were drilled into the surface without creating a mess. The process was quick, easy, effective, and didn’t require the building to be shut down during repairs. All of these factors played a major role in choosing polyurethane foam over traditional methods. Polyurethane foam fixed all soil issues without creating a burden on the soil. This makes polyurethane foam a permanent solution for concrete leveling.
In conclusion, TerraThane costs 60% less than concrete replacement so it was the best choice for concrete leveling. Mark Whitehead, an experienced engineer, commented that “polyurethane played a major role in saving a building so important to the hundreds of thousands of Mizzou alums and future Tigers.”
Read more about the Historic Memorial Union project.
Sinkhole Distribution in Missouri
Did you know sinkholes are a common feature in Missouri? Most areas of Missouri are susceptible to sinkholes due to frequent exposure to water and the type of rocks underlying the soil. There are over 15,000 sinkholes in Missouri, and a lot more exist that are not reported or documented. If you are a homeowner or property owner, it’s important to be aware of the development of sinkholes and the warning signs associated with them.
How do sinkholes develop? Sinkholes develop in karst terrains where the bedrock is dissolved by water. As it rains, water moves through cracks in the limestone and slowly dissolves the rock. Through this process, voids are formed and sinkholes develop on the surface. Over time, the voids become larger. As they continue to grow, they structurally impact homes and buildings, causing serious foundation problems. Also, sinkholes can occur on streets, parking lots, and in yards. Many sinkholes are circular when they collapse, while others are not visible on the surface.
How To Control Sinkholes in Missouri
Identify the Warning Signs
Unfortunately, sinkholes can develop over time or suddenly. They can form in all sizes, they can be deep or shallow, and can even be large or small.
The best way to identify sinkhole activity is to be aware of these common warning signs.
- Zigzag wall cracks
- Cracks located in the walls where windows and doors are present
- Ceiling and wall separating
- Depressions in your yard
- New water puddles in the yard
- Slumping trees, fence posts, or other objects
- Wilting vegetation
- Hard to open or close windows and doors
Controlling the Sinkhole
If you notice a hole, secure the sinkhole by using warning tape or a rope to make sure people stay away from it. Next, fill the hole with sand, then monitor the hole and watch for changes in its size. Notify your insurance company, then contact a city inspection department or a professional engineer.
How are voids detected? In addition to being used for foundation repair and slab lifting, a ground-penetrating radar (GPR) unit will be used to detect voids developed from sinkholes. A GPR has many advantages over X-ray methods. It uses a benign electromagnetic pulse and a high-frequency antenna to accurately locate voids. The GPR unit is portable to the site, making the process fast with instant results.
For more information about sinkholes and voids in the Missouri area, contact our team of experts.
What Causes Voids?
When voids form beneath the concrete, they can cause many issues such as settlement, cracking, and sinking foundations. These voids can form due to several reasons such as:
- Soil Shrinkage – When there are periods of hot and dry weather, soil shrinkage can form voids beneath foundations and concrete.
- Erosion – Excessive rainfall and melting snow can wash away the soil under your foundation and concrete creating voids.
- Hydrostatic Pressure – Heavy precipitation can also lead to an increase in hydrostatic pressure in the soil creating voids and causing the foundation to shift, settle, and sink.
- Heaving and Settling – Varying temperatures will cause the ground to freeze and thaw, which can cause voids to form.
As a home or business owner, you may not even be aware these voids are occurring. This is why it is important to contact a professional with experience in void detection. Polyjacking.com can inspect your home or business using a Ground Penetrating Radar (GPR) for void detection in Missouri and Kansas.
Using GPR to Find Voids
GPR uses a high-frequency radar antenna and advanced signal software to accurately locate voids and objects. GPR is fast, accurate, and inexpensive. This method of void detection detects embedded utilities, conduit, PVC, rebar, and tension cables. GPR prevents costly and potentially dangerous mistakes, such as cutting utilities or rebar. It is a much quicker and less disruptive method than other void detection methods such as X-rays.
If voids are detected, we use high-density polyurethane foam to fill the voids. This polyurethane foam will expand to over 20 times its liquid volume to fill the entire void. The curing time is quick, so you can use the affected area about 15 minutes after the repair is completed. Poly trucks are used for the installation process. This method is relatively simple.
- A small 5/8″ hole is drilled through the affected area.
- Using our highly specialized system, polyurethane foam is injected into the void. As it expands, it fills the entire void.
- Lastly, the holes are filled, the site cleaned up, and the equipment is removed.
Due to the short hardening time of the polyurethane material, the concrete surface is immediately ready for use. The dense polyurethane material is impervious to water preventing future erosion problems. Don’t let voids beneath your foundation or concrete cause you more expensive repairs. Contact the professionals at Polyjacking.com, a division of Pro Foundation Technology today!
Polyurethane Concrete Repair Products
What products do we use to fix your concrete? For over three decades, Polyjacking.com has used polyurethane foam and the proper poly equipment to level basement floors, pool decks, and concrete slabs. Polyurethane foam has been tested to withstand the toughest conditions. It is economical and efficient because it is cheaper than removing and replacing existing concrete. It only takes a few hours for the project to be finished. There is no need for future repairs. The polyurethane foam creates a hydraulic lift that allows us to control the lifting process accurately within 10/1000th of an inch. The foam cures within 15 minutes of injection, so you won’t have to wait days for the foam to cure and you can get back to using the slab almost immediately.
Ground Penetrating Radar
Before we level your concrete, we have to make sure there are no underground voids and objects. We use a Ground Penetrating Radar (GPR). GPR is a signal software with a high-frequency radar antenna to locate underground voids and objects. It is also used to locate utilities, tension cables, tendons, and PVC cables before we start construction. You don’t want to damage any systems that may be located under the slab.
Advantages of Polyurethane Foam
Polyurethane foam is also less disruptive and more durable than other methods, such as mudjacking. Because the curing time is so fast, lanes on a highway can be reopened immediately after the injection process. Nighttime would be the best time of the day to complete this process to minimize disruptions to people that need to use the area. Polyurethane foam is also strong and tough. It is even strong enough for roadway structures. The foam expands beneath the pavement filling every shape and size of all voids.
Polyurethane is a moisture seal barrier, moisture resistant, and lightweight. Also, it offers compaction ability. The base material gets stronger due to the material flowing into the sub-base and combining with soil particles. We choose to use TerraThane™ product line from NCFI because you won’t find a better product on the market today.
Contact Polyjacking.com for fast, accurate, and honest service. We are your polyurethane concrete lifting team for places like Kansas City, St. Louis, Dallas, and more.
Practical Applications for a GPR in Kansas City
Ground-penetrating radar, or GPR as many call it, has many practical uses, even though it seems like something that only scientists would use. Polyjacking.com uses it in many of its jobs because it tells us so much.
When it comes to the ground around your home or business, many problems can occur. Voids can form underground, along with other geological features, including groundwater resources. We can use the radar to easily detect voids with a high level of accuracy. This can prevent damage from voids to roads, slabs, highways, runways and more.
Our team of experts can perform concrete inspections using GPR. There can be objects such as PVC, cables, rebar, conduit, and more obstacles you may want to know about before you dig!
GPR Finds Underground Objects
GPR is extremely useful in geological or forensic applications. The professionals at Polyjacking.com can use GPR to locate and image underground wells, storage tanks, rock shelves, and even unmarked gravesites.
Most people don’t even think about using GPR on bridges. We can use ground-penetrating radar to check for safety issues with bridge decks and check for voids and cracks in bridges.
GPR is highly accurate using high-frequency antennas and a computer signal analysis to make sure that the image you are seeing is just right and also in real-time. We can render 3-D images to locate features or objects using an x, y, and z-axis. Since our radar units are portable, we can have them to a site quickly and have results from our technicians immediately. Plus, since they use electromagnetic pulse, you don’t have the concerns about radiation that you might have from an X-ray machine.
So, GPR is not as odd as one might think. There are many practical applications and reasons for ground-penetrating radar. Polyjacking.com proudly offers this service and would love to show you how ground penetrating radar can work for you. Call us today!
Call us today at 1-800-724-3076 or 816-832-2558 or click here to email us. We look forward to helping you keep your property strong, stable, and safe.