GEOTHERMAL TECHNOLOGIES LEGACY COLLECTION - Bibliographic Citation


Bibliographic Citation



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Full Text: Citation URL: http://www.osti.gov/geothermal/product.biblio.jsp?osti_id=1049212
Title: Effect of MgO Additive on Volumetric Expansion of Self-Degradable Cements
Creator/Author: Sugama T. ; Warren, J. ; Butcher, T.
Publication Date:2011 Sep 30
OSTI Identifier:OSTI 1049212
Report Number(s):BNL--96339-2011-IR
DOE Contract Number:DE-AC02-98CH10886
Document Type:Technical Report
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Research Org:BROOKHAVEN NATIONAL LABORATORY (BNL)
Sponsoring Org:USDOE EE OFFICE OF ENERGY EFFICIENCY & RENEWABLE ENERGY (EERE)
Subject:15 GEOTHERMAL ENERGY; ADDITIVES; CALCIUM SILICATES; CEMENTS; FLY ASH; FRACTURES; GEOTHERMAL SYSTEMS; HYDRATION; MAGNESIUM OXIDES; PERFORMANCE; PLUGGING; SODIUM
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Description/Abstract:We identified hard-burned magnesium oxide (MgO) as a suitable expansive additive for improving the plugging performance of self-degradable, temporary sodium silicate-activated slag/Class C fly ash (SSASC) blend cement sealers into rock fractures in Enhanced Geothermal Systems (EGSs). MgO extended the volumetric expansion of sealers during their exposure to a hydrothermal environment at 200 C under pressures, ranging from 300 to 1500 psi. A great expansion ratc of 19.3% was observed by adding 3.0 wt% MgO under 300 psi pressure, thus promising to plug thoroughly inner fracture. When the pressure was increased from 300 psi to 1500 psi, the expansion rate of cement markedly reduced, corresponding to the formaLion of crack-free specimens and the improvement of compressive strength. However, with 3.0 wt% MgO, the specimens still engendered the generation of numerous visual cracks, although they were prepared under a high pressure of 1500 psi. The effective content of MgO in minimizing and eliminating the generation of cracks was 2.0 wt%, which provided a moderate expansion of {ge} 0.5%. The compressive strength of 2.0 wt% MgO specimens made under a pressure of 300 psi rose {approx} 1.7-fold to 4816 psi with an increasing pressure to 1500 psi. The in-situ growth of brucite crystal formed by the hydrothermal hydration of MgO was responsive for such an expansion of the SSASC cement; meanwhile. two crystalline hydrothermal reaction products, 1.1 nm tobermorite and calcium silicate hydrated, contributed to the development of the sealer's compressive strength. Thus, the increasing pressure seems to suppress and control a growth rate of brucite crystal in response to a lower extension of expansion. Furthermore, all MgO-conlaining SSASC sealers possessed the water-catalyzed self-degradable properties.
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Country of Publication:US
Language:English
Size/Format:Medium: ED
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System Entry Date:2012 Dec 05
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