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Synergistic effect of expanded graphite-silane functionalized silica as a hybrid additive in improving the thermal conductivity of cementitious grouts with controllablewater uptake
Sabanci University, Turkey.
RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
Cimsa Cimento Sanayi AS, Turkey.
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2020 (English)In: Energies, E-ISSN 1996-1073, Vol. 13, no 14, article id 3561Article in journal (Refereed) Published
Abstract [en]

Recently, a growing demand for geothermal applications has led to the exploitation of energy efficiently by developing grouting materials in the borehole between pipes and the ground. Therefore, the current study developed newly formulated cementitious grouts by the integration of expanded graphite (EG)-based hybrid additives synthesized by building chemical bridges between silica particles and EG in the presence of amino functional silane coupling agents. These produced hybrid additives with controlled EG and silica ratios were utilized in grout mixtures used in borehole heat exchangers to enhance the thermal conductivity. According to the optimization study on the formulation development of grout mixtures with bentonite, silica sands, cement, and superplasticizer by adding neat EG and EG-based hybrids, the relationship between the carbon amount and water demand was found to have a significant impact on thermal conductivity. The highest thermal conductivity value of 2.656 W/mK was achieved by the incorporation of 5 wt% hybrid additive with the ratio silica/EG of 1:5 compared to the reference grout, which showed a thermal conductivity of 2.373 W/mK. Therefore, the enhancement in thermal conductivity was dependent on the increase in the EG content and also the additive loading ratio, resulting in a slight increase in the water demand.

Place, publisher, year, edition, pages
MDPI AG , 2020. Vol. 13, no 14, article id 3561
Keywords [en]
Cement-based composites, Cementitious grout, Expanded graphite, Ground source heat exchangers, Hybridization, Silanization, Thermal conductivity, Additives, Boreholes, Coupling agents, Geothermal energy, Graphite, Grouting, Mixtures, Mortar, Silanes, Silica, Borehole heat exchangers, Formulation development, Functionalized silica, Geothermal applications, Grouting materials, Optimization studies, Silane coupling agent, Synergistic effect
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-48896DOI: 10.3390/en13143561Scopus ID: 2-s2.0-85090505460OAI: oai:DiVA.org:ri-48896DiVA, id: diva2:1470402
Note

Export Date: 22 September 2020; Article; Funding details: Horizon 2020, 727583; Funding text 1: Funding: This project is supported by Horizon 2020 project of GEOCOND. The grant number is 727583.

Available from: 2020-09-24 Created: 2020-09-24 Last updated: 2023-08-28Bibliographically approved

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