skip to main content

DOE PAGESDOE PAGES

Title: Phase Changes of Monosulfoaluminate in NaCl Aqueous Solution

Monosulfoaluminate (Ca 4Al 2(SO 4)(OH) 12∙6H 2O) plays an important role in anion binding in Portland cement by exchanging its original interlayer ions (SO 4 2- and OH -) with chloride ions. In this study, scanning transmission X-ray microscope (STXM), X-ray absorption near edge structure (XANES) spectroscopy, and X-ray diffraction (XRD) were used to investigate the phase change of monosulfoaluminate due to its interaction with chloride ions. Pure monosulfoaluminate was synthesized and its powder samples were suspended in 0, 0.1, 1, 3, and 5 M NaCl solutions for seven days. At low chloride concentrations, a partial dissolution of monosulfoaluminate formed ettringite, while, with increasing chloride content, the dissolution process was suppressed. As the NaCl concentration increased, the dominant mechanism of the phase change became ion exchange, resulting in direct phase transformation from monosulfoaluminate to Kuzel’s salt or Friedel’s salt. The phase assemblages of the NaCl-reacted samples were explored using thermodynamic calculations and least-square linear combination (LC) fitting of measured XANES spectra. A comprehensive description of the phase change and its dominant mechanism are discussed.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5] ;  [3]
  1. Kyonggi Univ., Suwon (Korea, Republic of). Dept. of Civil Engineering; Ulsan National Inst. of Science and Technology (UNIST), Ulsan (Korea, Republic of). School of Urban and Environmental Engineering
  2. Kean Univ., Union, NJ (United States). School of Environmental and Life Sciences
  3. Univ. of California, Berkeley, CA (United States). Dept. of Civil and Environmental Engineering
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source
  5. Ulsan National Inst. of Science and Technology (UNIST), Ulsan (Korea, Republic of). School of Urban and Environmental Engineering
Publication Date:
Grant/Contract Number:
AC02-05CH11231; 2015K000130; NRF-2014R1A1A3052424
Type:
Accepted Manuscript
Journal Name:
Materials
Additional Journal Information:
Journal Volume: 9; Journal Issue: 5; Journal ID: ISSN 1996-1944
Publisher:
MDPI
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ulsan National Inst. of Science and Technology (UNIST), Ulsan (Korea, Republic of)
Sponsoring Org:
USDOE Office of Science (SC); National Research Foundation of Korea (NRF); Ministry of Science, ICT & Future Planning (MISP) (Korea, Republic of)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; cement chemistry; STXM; XANES; chloride; Kuzel's salt; Friedel's salt; monosulfate
OSTI Identifier:
1414742