Thermal Grouting
Been There. Grouted That.™
The long-term success of trenchless high-voltage electrical installations depends on effective heat management. Buried power cables generate significant heat, and without a stable thermal backfill, they risk overheating and failure. CJGeo solves this critical challenge with expert thermal grouting. We use highly conductive thermal grout to backfill conduits, creating a stable path for heat to dissipate safely away from the essential infrastructure. This method of thermal grouting is essential for modern utility protection.
Typical Thermal Grouting Mix Design
CJGeo has developed multiple thermal grout mixtures. Each has been tested by GeoTherm, which is a standard industry requirement. Thermal grouts are typically specified by a maximum thermal resistivity, which is measured in rho. Generally, as grout dries, rho decreases, as the evaporating water leaves small voids. These voids are filled with air, which increases thermal resistivity.
Maximum allowable thermal resistivity values vary by utility owner. Most have a maximum allowable thermal resistivity at 0% moisture content, often accompanied by a maximum value at a single digit moisture content such as 4% or 6%. Occassionally, the critical moisture level is used as a specifying point. Critical moisture level is the intercept of the two distinct slopes in a dryout curve.
Conduit Buoyancy Considerations
Carrier buoyancy is a function of the grout density. Thermal grouts are inherently heavy, due to their high silica content and nominal air content.
Buoyancy management is typically done with water filling and designing conduit bundles tolerant of some uplift.
Relative Grouting Pressures
CJGeo’s thermal grout mixtures are designed with flow cone times of less than 45 seconds. This very high fluidity, but with very low water:cement ratios ensures stability during placement, and very low placement pressures. Placement pressures during thermal grouting operations are typically measured with in-annulus pressure/thermistor cells. As distance and head increase, pressure increases. This pressure can be managed by installing multiple sacrificial injection lines in the annulus.
Speak With An Expert
Facing a thermal grouting challenge? Kirk Roberts, VP Preconstruction, 804-396-4845.
