Thermal, physical, hydraulic and heat of hydration properties of cement-based grouts. Final report
Technical Report
·
OSTI ID:354864
The objective of this research was to examine the properties of cement based grouts and performance characteristics relevant in grouted geothermal bores. Physical properties that were investigated included thermal conductivity, shrinkage, and volumetric yield. Thermal conductivity of partially saturated neat cement pastes ranged from 0.45 to 0.65 Btu/hr ft F. Thermal conductivity decreased for samples with higher water/cement ratios and also for samples with a lesser degree of saturation. Addition of sand increased the thermal conductivity up to 1.25 Btu/hr ft F with 60% masonry sand and 1.60 Btu/hr ft F with 60% silica sand. Bentonite and cement mixtures showed decreasing thermal conductivities with increasing percentages of bentonite. Shrinkage tests run on cement based samples showed small amounts of shrinkage after initial setup. Linear shrinkage was less than 3.5% for all mixtures tested. The volumetric yield of cement grouts increased with increasing percentages of both bentonite and sand, but had opposite effects on slurry weight. Sand increased /the slurry weight, while bentonite decreased the slurry weight of the mixture. The effects of heat of hydration on loop pipes was examined through laboratory testing to discover heat generation rates of cement grout and modeling of cement grouted bores with a finite difference program. Parameters included in the model were cement type, bore diameter, and formation properties. While a peak temperature can be predicted, damage to loop pipes would depend upon the ability of a specific brand of pipe to handle the pressures associated with the particular situation at the calculated peak temperature. Possible problems associated with loss of contact between the loop pipes and cement grout were examined from a permeability and a thermal perspective. Cold loop temperatures (35 F) caused increased coefficients of permeability for all cement mixtures tested, ranging from 5 {times} 10{sup {minus}6} to 5 {times} 10{sup {minus}5} cm/sec. Thermal test results on cement mixtures indicated potential resistance increases with cold loop temperatures and repeated cycling of loop temperatures from hot to cold. Limited temperature differences across the test specimen limited the ability to calculate accurate thermal resistance values.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (United States); South Dakota State Univ., Brookings, SD (United States)
- Sponsoring Organization:
- Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 354864
- Report Number(s):
- EPRI-TR--109165
- Country of Publication:
- United States
- Language:
- English
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