QUESTIONS & ANSWERS

In the mid-1990's, GeoPro, Inc. was formed to bring the idea of thermally-enhanced grouting materials to the GeoExchange industry. We have successfully achieved our original objective as evidence to your interest in this area of our website.

We are committed to continuing our efforts to bring innovative ideas that improve or assure system performance while offering system cost reduction to this rapidly growing industry. We are committed to backing our products and services with scientific research and a technical and practical understanding of how this technology works.

Below is a list of commonly asked questions related to the application and use of our products:

Hydraulic Conductivity (Permeability) Verification
Thermal Conductivity Verification
Thermal Enhancement Compound (Silica Sand)
Matching Grout Thermal Conductivity to Formation Thermal Conductivity
Pumping Thermal Grout
Pumping Through Problem Formations
Submit a Question

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Hydraulic Conductivity (Permeability) Verification

Q: As the design engineer, how do I know if the thermally-enhanced grouting material that I allow to be used meets our state's maximum permeability requirement and is this something I should be concerned about?

A: Absolutely you should be concerned!  Not all thermally-enhanced grouts can or will meet your state's legal requirement for maximum permeability.

The first step in making this determination is to determine your state's grouting requirement and determine what value they require as a MAXIMUM permeability value (this is usually expressed in units of cm/sec). Once you have determined the MAXIMUM permeability requirement, you should require verification of the mixed material from an independent laboratory, by a NICET certified lab technician. The lab should be required to perform the test per ASTM D-5084, Method C. GeoPro has already had an independent laboratory perform such tests and is willing to supply a copy of the analysis anytime it is requested.

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Thermal Conductivity Verification

Q: As the design engineer, I know that improper loopfield performance may not "surface" for several years. With that in mind, how can I be assured that the thermal conductivity value that I assumed in the design process is actually installed?

A: As you indicated, the long-term system performance is critical to the "installed" thermal performance of the loopfield. The published thermal conductivity (TC) values provided by GeoPro are considered MINIMUM values and should easily be achieved by the contractor when following our mixing instructions for a specific TC. GeoPro shares your concern about "field quality control" and achieving the TC value needed to ensure proper system performance. For these reasons, GeoPro began offering TC verification of field collected samples (see our SUPPORT SERVICES web page for details) in 1999. GeoPro measures the thermal conductivity of these samples in accordance with ASTM D-5334.

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Thermal Enhancement Compound (Silica Sand)

Q: Why can't we use sand from a local source as the "Thermal Enhancement" additive in your Thermal Grout products?

A: Today, you can! GeoPro recommends that the drilling contractor explore the various sand sources available close to the project site. We ask that the contractor obtain at least a 15 lb. sample of the finest sand available and send to GeoPro for evaluation along with information on the thermal conductivity that is being specified by the design engineer. Once the sample is received, GeoPro will determine the thermal conductivity of the sample and will offer an adjusted recipe if necessary to achieve the specified value. However, since GeoPro will not be supplying the additive material, we will not take any responsibility for the final delivered thermal conductivity on this project.

In some cases, locally obtained sand may not be able to satisfy the specified thermal conductivity value for your project. In this case, GeoPro will provide alternative recommendations (see our SUPPORT SERVICES web page for details).

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Matching Grout Thermal Conductivity to Formation Thermal Conductivity

Q:  Should I try to match the thermal conductivity of the grout with thermal conductivity of the formation and how do I determine the thermal conductivity of the formation?

A:  Absolutely not!  If you are a designer, you should look at the impact that the grout thermal conductivity has on the design and select a specific value based on its ability to impact the installation cost.  When doing the calculations to determine the proper ground loop design, the effect of the grout thermal conductivity is independent of the formation thermal conductivity. As an example, if you see a 40’ per ton reduction due to selecting a specified grout thermal conductivity when compared to a grout with a lower thermal conductivity value, you will see that same 40’ per ton reduction regardless of the formation thermal conductivity.  This is true because the calculated impact is based on the thermal conductivity in the bore annulus, not the formation.

Visit this page for more information on the subject.

How do you determine the formation thermal conductivity? The most accurate method would be to contact a professional testing company with experience in doing so. However, if your project is less than 25 tons, running a formation thermal conductivity test probably wouldn't be cost effective. In that case, you can use the drill log information and attempt to calculate a weighted-average formation thermal conductivity value. You will always want to assume a conservative value (lower value) when exercising this approach.

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Pumping Thermal Grout

Q: I have heard that it takes a special type of grout pump to be able to pump your Thermal Grout products, why can't I use a pump that I already own?

A: The thermal enhancement compound recommended for use in our Thermal Grout products is high-grade silica sand. When properly mixed, Thermal Grout will prove to be extremely abrasive to most types of positive displacement pumps. Research and field experience has proven that a piston-style pump offers the best results with the least amount of maintenance cost. As a contractor, you should know that it is recommend that the pump be a "grout" pump and not a "mud" pump. "Grout" pumps are designed to deliver the high pressures and low volumes that are typically required for proper placement with most commercially available thermally-enhanced grouting products in the market today. "Mud" pumps deliver high volumes at low pressures which are not usually adequate for proper grout placement.

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Pumping Through Problem Formations

Q: On rare occasions, we encounter formations that require an excessive amount of your Thermal Grout product to be pumped into it before we see material coming to the surface. Is there anything that we can do to reduce loss to formations?

A: Yes. When you encounter problem formations that are extremely porous (such as highly-fractured consolidated formations, large crevasses, small caverns or flow aquifers), we recommend that you use a granular material such as our 3/8" Bentonite Plug through the problem area only. We suggest that you grout from the bottom to the problem area, place the granular material through the problem area then finishing grouting to the top of the bore with the specified material. Typically, this small amount of material (with a considerably lower thermal conductivity value) will not significantly reduce the overall average thermal conductivity of the bore annulus. We recommend that you contact GeoPro and let us help you determine if any corrections need to be made when encountering a problem similar to the one being questioned above.

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Customer Service (Orders): CustomerService@GeoProInc.com

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RCarda@GeoProInc.com