SUGGESTED SPECIFICATIONS
Grouting Materials for Ground-Loop Heat Exchangers on Closed-Loop Ground Source Heat Pump Systems

NON-THERMALLY ENHANCED BENTONITE GROUT

PART 1 - GENERAL

Bentonite grout shall be used to seal and backfill each geothermal bore of the closed-loop ground heat exchanger to ensure proper thermal contact with the earth and to ensure the environmental integrity of each bore. The grouting material shall remain in a plastic state (moldable) throughout the life of the system and shall not generate heat during the hydration process.

No other backfill material shall be accepted.

Manufacturer's published product submittal information sheet(s) shall be submitted with the bid package. Submittals shall include mixing instructions, minimum thermal conductivity performance, maximum permeability, total percent solids, percent active solids, grout weight and unit yield along with verification of the required listing(s).

The grouting material shall be certified and listed according to NSF (National Sanitation Foundation International) to ANSI/NSF Standard 60, "Drinking Water Treatment Chemicals - Health Effects".

Grouting material shall consist of a bentonite base with no additional chemical or thermal additives. The bentonite base shall be either BH20, one of the Thermal Grout products supplied by GeoPro, Inc. or a pre-approved equivalent. Approved suppliers are GeoPro, Inc. or pre-approved equivalent.

The minimum solids concentration of the grouting material shall be NaN%, which corresponds to a thermal conductivity value of NaN Btu/hr-ft-°F, as determined when tested in accordance to ASTM D-5334, "Standard Test Method for Determination of Thermal Conductivity of Soils and Soft Rock by Thermal Needle Probe Procedure" per International Ground Source Heat Pump Association (IGSHPA) Standard 2B.3.2.

The grout mixture shall have a maximum permeability rate of 1.0 x 10-7 cm/s as determined by ASTM D-5084, "Measurement of Hydraulic Conductivity of Saturated Porous Materials using a Flexible Wall Permeameter, Method C - test with increasing tailwater level", per IGSHPA Standard 2B.3.3, with a 5 psi confinement pressure (to simulate an approximate sample depth of 5 ft).

The reported permeability shall be verified by an independent, lab certified by AMRL (American Association of State Highway & Transportation Officials, Materials Reference Laboratory) and validated by the US Army Corps of Engineers to perform ASTM D-5084 at the time of verification as per IGSHPA Standard 2B.3.2.1. A copy of the report shall be supplied upon request from the engineer. Credentials of the independent laboratory shall also be supplied upon request from the engineer.

Within 4 hours of being pressure pumped in the bore annulus, the installed material will have the consistency of moldable putty.

The bentonite component of the grouting mix shall be manufactured and packaged such that it is ready for field mixing prior to delivery to the job site. Bulk materials that require on site handling such as grinding, sieving, drying or other processing prior to being mixable will not be accepted.

The grouting material shall be mixed according to manufacturer's written instructions as provided on manufacturer’s product submittal.

Grout material shall be pressure pumped through a 1 inch, 1-1/4 inch or a 1-1/2 inch nominal diameter tremie pipe and placed in the bore column from the bottom to the top (or from end to end in horizontally-bored applications). Grouting process shall conform to the manufacturer's instructions and "Grouting for Vertical Geothermal Heat Pump Systems -- Engineering Design and Field Procedures Manual", as published by the IGSHPA, Oklahoma State University (OSU), 2000. The grout column shall be brought to ground level to ensure complete fill of the bore annulus.

3.3 INSPECTION

Settling may occur after initial placement of the grout material. The contractor shall monitor each borehole for a period of 24-48 hours and continue adding grout as required.