The Self-Degradation Mechanism of Polyvinyl Chloride-Modified Slag/Fly Ash Binder for Geothermal Wells

Huijing Tan, Xiuhua Zheng, Long Chen, Kang Liu, Wenxi Zhu and Bairu Xia
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Huijing Tan: School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China
Xiuhua Zheng: School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China
Long Chen: School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China
Kang Liu: School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China
Wenxi Zhu: School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China
Bairu Xia: School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China

Energies, 2019, vol. 12, issue 14, 1-16

Abstract: Polyvinyl chloride (PVC) releases hydrochloric acid (HCl) during its thermal degradation, and hydrochloric acid can react with hydration products of alkali-activated binders. According to this characteristic of PVC and the temperature change that occurs during the development of a geothermal well, the PVC was added into slag/fly ash binder to develop self-degradable materials. The thermal degradation properties of PVC, compressive strength, hydration products, and microstructure of binders at different stages were tested, in order to study the degradation mechanism of the material. It was found that 20% PVC reduced the compressive strength, decreasing the level of binder from 13.95% to 76.63%. The mechanism of PVC promoting the material degradation mainly includes the following: (1) the thermal degradation of PVC increases the number of multiple damage pores in the material, at a high temperature; (2) HCl generated by the PVC thermal degradation reacts with the binder gels, and breaks them into particles; and (3) HCl also reacts with other substances in the binder, including CaCO 3 and NaOH in the pore solution.

Keywords: geothermal wells; alkali-activated slag/fly ash binder; self-degradation; polyvinyl chloride (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
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