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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 controllable water uptake

Berktaş, İlayda and Ghafar, Ali Nejad and Fontana, Patrick and Çaputcu, Ayten and Menceloğlu, Yusuf Z. and Saner Okan, Burcu (2020) Synergistic effect of expanded graphite-silane functionalized silica as a hybrid additive in improving the thermal conductivity of cementitious grouts with controllable water uptake. Energies, 13 (14). ISSN 1996-1073

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Official URL: http://dx.doi.org/10.3390/en13143561

Abstract

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.

Item Type:Article
Uncontrolled Keywords:expanded graphite; silanization; hybridization; thermal conductivity; cementitious grout; cement-based composites; ground source heat exchangers
Subjects:T Technology > TA Engineering (General). Civil engineering (General) > TA401-492 Materials of engineering and construction. Mechanics of materials
T Technology > TA Engineering (General). Civil engineering (General) > TA630-695 Structural engineering (General)
Q Science > QD Chemistry
ID Code:40995
Deposited By:Burcu Saner Okan
Deposited On:26 Sep 2020 19:13
Last Modified:26 Sep 2020 19:13

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