Applicability of cement-based grout for ground heat exchanger considering heating-cooling cycles

作     者：Moonseo PARK SunhongMIN Jeehee LIM Jong Min CHOI Hangseok CHOI 

作者机构：School of civil Environmental and Architectural Engineering Korea University Seoul Republic of Korea Department of Mechanical Engineering Hanbat National University Daejeon Republic of Korea 

出 版 物：《Science China(Technological Sciences)》 (中国科学（技术科学英文版）)

年 卷 期：2011年第54卷第7期

页      面：1661-1667页

核心收录：

学科分类：080705[工学-制冷及低温工程] 08[工学] 0807[工学-动力工程及工程热物理] 

基　　金：supported by the Fundamental Research and Development Program of the Center of New and Renewable Energy of the Ministry of Knowledge and Economy (Grant No. 2008-N-GE08-R-01) the National Research Foundation of Korea Grant funded by the Korean Government (Grant No. 2010-0011159) 

主　　题：cement grout bentonite grout thermal conductivity workability equivalent permeability coefficient 

摘      要：The applicability of cement grout （or cement-based grout） has been considered as an alternative to bentonite grout commonly used to backfill closed-loop vertical ground heat exchangers. In a geothermal heat pump system, repeated heating-cooling cycles may cause adverse effects on the integrity of cement grout in the ground heat exchanger. To account for the temperature cycling effect, the strength degradation of cement grout due to temperature cycling has been examined by measuring the unconfined compression strength of cured specimens in a humidity-temperature controlling chamber with applying temperature cycles between -5℃ and 50℃. There is a tendency that the unconfined compression strength decreases with an increase in the number of temperature cycles. On the other hand, an equivalent hydraulic conductivity of a pipe-embedded cement grout specimen was evaluated by carrying out a modified flexible wall permeameter test equipped with a water circulating system to control temperature inside the pipe section. The applied operating temperature range was from 5 to 35℃. After three cycles of heating-cooling circulation, the equivalent hydraulic conductivity becomes asymptotic to a constant value, which implies there is no severe detachment of the pipe from the cement grout.