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Title: Supercritical drying of cementitious materials

Abstract

Techniques to characterize the microstructure of hydrated cement require dried materials. However, the microstructure of hydrated products is significantly altered by high capillary forces during drying when using the conventional drying methods. To avoid drying stresses when preparing samples, we have employed supercritical drying (SCD) which has been used for decades to prepare aerogels that undergo no shrinkage during drying, but has rarely been used for cementitious materials. The pore solution is first replaced with isopropanol, and then with trifluoromethane (R23). The temperature and pressure are raised above the critical point, where no menisci or capillary pressure can exist; therefore, the dried samples are free of artifacts created by stresses. Images from scanning electron microscope show less compact morphology for supercritically dried samples than that dried by conventional methods, while BET surface areas of SCD samples are very close to samples dried by the isopropanol replacement method. This can be explained by the fact that isopropanol and supercritical fluid enter the micropores and block them. The nature of the chemical interactions of isopropanol and R23 with cement pastes are still not clear, but no reaction products were identified in the present study.

Authors:
;
Publication Date:
OSTI Identifier:
22701568
Resource Type:
Journal Article
Journal Name:
Cement and Concrete Research
Additional Journal Information:
Journal Volume: 99; Other Information: Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0008-8846
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DRYING; ELECTRON SCANNING; FLUORINE COMPOUNDS; PROPANOLS; SCANNING ELECTRON MICROSCOPY; SURFACE AREA

Citation Formats

Zhang, Zhidong, and Scherer, George W., E-mail: scherer@princeton.edu. Supercritical drying of cementitious materials. United States: N. p., 2017. Web. doi:10.1016/J.CEMCONRES.2017.05.005.
Zhang, Zhidong, & Scherer, George W., E-mail: scherer@princeton.edu. Supercritical drying of cementitious materials. United States. doi:10.1016/J.CEMCONRES.2017.05.005.
Zhang, Zhidong, and Scherer, George W., E-mail: scherer@princeton.edu. Fri . "Supercritical drying of cementitious materials". United States. doi:10.1016/J.CEMCONRES.2017.05.005.
@article{osti_22701568,
title = {Supercritical drying of cementitious materials},
author = {Zhang, Zhidong and Scherer, George W., E-mail: scherer@princeton.edu},
abstractNote = {Techniques to characterize the microstructure of hydrated cement require dried materials. However, the microstructure of hydrated products is significantly altered by high capillary forces during drying when using the conventional drying methods. To avoid drying stresses when preparing samples, we have employed supercritical drying (SCD) which has been used for decades to prepare aerogels that undergo no shrinkage during drying, but has rarely been used for cementitious materials. The pore solution is first replaced with isopropanol, and then with trifluoromethane (R23). The temperature and pressure are raised above the critical point, where no menisci or capillary pressure can exist; therefore, the dried samples are free of artifacts created by stresses. Images from scanning electron microscope show less compact morphology for supercritically dried samples than that dried by conventional methods, while BET surface areas of SCD samples are very close to samples dried by the isopropanol replacement method. This can be explained by the fact that isopropanol and supercritical fluid enter the micropores and block them. The nature of the chemical interactions of isopropanol and R23 with cement pastes are still not clear, but no reaction products were identified in the present study.},
doi = {10.1016/J.CEMCONRES.2017.05.005},
journal = {Cement and Concrete Research},
issn = {0008-8846},
number = ,
volume = 99,
place = {United States},
year = {2017},
month = {9}
}