TY - JOUR
T1 - Nanoscale Chemical Degradation Mechanisms of Sulfate Attack in Alkali-activated Slag
AU - Gong, Kai
AU - White, Claire Emily
N1 - Funding Information:
This work was supported by the National Science Foundation under Grant No. 1362039. The authors would like to acknowledge the use of the 11-ID-B beamline at the Advanced Photon Source, an Office of Science User Facility operated for the U.S. DOE Office of Science by Argonne National Laboratory, under U.S. DOE Contract No. DE-AC02-06CH11357. The authors also acknowledge the beamline staff Mr. Kevin Beyer and Dr. Olaf Borkiewicz for their assistance and guidance. The authors would like to thank Prof. Andrew B. Bocarsly for providing access to the FTIR instrument in the Frick Chemistry Laboratory at Princeton University, Dr. Nishant Garg and Mr. Eric McCaslin for their assistance during the synchrotron experiment, and Ms. Maya Ravichandran and Mr. Kengran Yang for their assistance with sample preparation.
Funding Information:
This work was supported by the National Science Foundation under Grant No. 1362039. The authors would like to acknowledge the use of the 11-ID-B beamline at the Advanced Photon Source, an Office of Science User Facility operated for the U.S. DOE Office of Science by Argonne National Laboratory, under U.S. DOE Contract No. DE-AC02-06CH11357.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/3/22
Y1 - 2018/3/22
N2 - Chemically induced material degradation is a major durability issue facing many technologically important materials systems, including conventional and new sustainable cementitious materials. In this study, the nanoscale chemical degradation mechanisms have been elucidated for an amorphous sodium hydroxide-activated slag paste (one type of sustainable cement) exposed to different types of sulfate-bearing solutions (i.e., Na2SO4, MgSO4, and H2SO4), by combining synchrotron-based X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and X-ray pair distribution function (PDF) analysis. The XRD, FTIR, and PDF results show that the chemistry and structure of the paste is essentially immune to Na2SO4 attack, whereas exposure to 5-10 wt % MgSO4 and H2SO4 cause complete disintegration of the main binder gel (i.e., sodium-containing calcium-(alumino)-silicate-hydrate), along with formation of magnesium-silicate-hydrate or silica-rich gels and extensive precipitation of gypsum. These differences appear to be directly correlated with the ability of the ions (i.e., Na+, Mg2+, H+) accompanying SO42- to alter the pH of the pore solution in the samples. By correlating the changes that occurred to the phase composition and the structure of the paste with the pH data from the equilibrated solutions, this study has provided important mechanistic insight on the fundamental sulfate-induced degradation reactions occurring in hydroxide-activated slag.
AB - Chemically induced material degradation is a major durability issue facing many technologically important materials systems, including conventional and new sustainable cementitious materials. In this study, the nanoscale chemical degradation mechanisms have been elucidated for an amorphous sodium hydroxide-activated slag paste (one type of sustainable cement) exposed to different types of sulfate-bearing solutions (i.e., Na2SO4, MgSO4, and H2SO4), by combining synchrotron-based X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and X-ray pair distribution function (PDF) analysis. The XRD, FTIR, and PDF results show that the chemistry and structure of the paste is essentially immune to Na2SO4 attack, whereas exposure to 5-10 wt % MgSO4 and H2SO4 cause complete disintegration of the main binder gel (i.e., sodium-containing calcium-(alumino)-silicate-hydrate), along with formation of magnesium-silicate-hydrate or silica-rich gels and extensive precipitation of gypsum. These differences appear to be directly correlated with the ability of the ions (i.e., Na+, Mg2+, H+) accompanying SO42- to alter the pH of the pore solution in the samples. By correlating the changes that occurred to the phase composition and the structure of the paste with the pH data from the equilibrated solutions, this study has provided important mechanistic insight on the fundamental sulfate-induced degradation reactions occurring in hydroxide-activated slag.
UR - http://www.scopus.com/inward/record.url?scp=85044384179&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85044384179&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.7b11270
DO - 10.1021/acs.jpcc.7b11270
M3 - Article
AN - SCOPUS:85044384179
SN - 1932-7447
VL - 122
SP - 5992
EP - 6004
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 11
ER -