Thermal conductivity of cement stone modified with superfine graphite

SU Xiaoyue; LIU Pingjiang; ZHANG Ye; TIAN Baozhen; GAO Fei; MEI Kaiyuan; CHENG Xiaowei

doi:10.13732/j.issn.1008-5548.2023.06.006

Abstract：In order to improve the exploitation efficiency of geothermal energy,cementing materials with high thermal conductivity should be used in the heat recovery section of geothermal wells.Superfine graphite was used as an admixture to improve thermal conductivity,and sodium dodecyl benzene sulfonate was used as a dispersant to improve the dispersion stability of superfine graphite in cement slurry.After the suitable superfine graphite dispersion was selected,superfine graphite composite modified cement stones(referred to as cement stones)were further prepared as the cement materials.The effects of superfine graphite content on compressive strength and thermal conductivity of cement stones were studied.The phase composition,porosity and structural compactness of cement stones were tested and characterized by XRD,TG,MIP and SEM.The effects of different contents of superfine graphite on the thermal conductivity of cement stones were studied.The thermal conductivity mechanism of cement stones under different graphite contents and porosity were discussed also.The results show that with the increase of the content of superfine graphite,the thermal conductivity of cement stones first increases and then decreases.When the content of superfine graphite is 12％,the thermal conductivity of cement stone reaches the maximum value of 2.45 W/(m·K).The high thermal conductivity of superfine graphite,the porosity and the mass fraction of hydration products can affect the thermal conduc-tivity of cement stone.With the increase of superfine graphite content,the compressive strength of cement stones first increases and then decreases.Considering the thermal conductivity and mechanical properties of cement stones,the optimal mass fractions of superfine graphite should be from 10％to 12％.