Microstructure and bonding between calcium aluminate cement-containing gahnite–alumina matrix and refractory aggregates

Rajat Durgesh Ramteke; James G. Hemrick; Manoj K. Mahapatra

doi:10.1111/jace.70221

Microstructure and bonding between calcium aluminate cement-containing gahnite–alumina matrix and refractory aggregates

Rajat Durgesh Ramteke, James G. Hemrick, Manoj K. Mahapatra

Research output: Contribution to journal › Article › peer-review

Abstract

Calcium aluminate cement enhances the thermomechanical properties of refractory castables through the formation of acicular calcium hexaluminate (CaO·6Al₂O₃), Ca₂Mg₂Al₂₈O₄₆ (CAM-I), and CaMg₂Al₁₆O₂₇ (CAM-II) phases in MgO- or MgAl₂O₄-containing castables. The compatibility of CA₆ with gahnite (ZnAl₂O₄), and acicular Ca₂Zn₂Al₂₈O₄₆ (CAZ-I) and CaZn₂Al₁₆O₂₇ (CAZ-II) phases formation have been previously reported. In this work, the interaction between a CAC binder containing ZnAl₂O₄-Al₂O₃ matrix with commonly used refractory aggregates such as tabular alumina (TA), alumina-rich (AR90, AR78) and stoichiometric (SM72) MgAl₂O₄ spinels, and fused and dead-burned magnesia (FM, DBM, respectively) were investigated at 1650°C for 5 h. Microstructural analysis, using digital microscopy, scanning electron microscopy, and energy dispersive spectroscopy, revealed the formation of acicular CaZn_0.18Al_11.82O_18.91, CAZ-I and CAZ-II grains, and strong interfacial bonding between the matrix and TA and spinel aggregates. FM and DBM were found to debond from the matrix. Thick interface layers were observed between the matrix and all the aggregates but TA. Null hypothesis significance testing (NHST) shows that the difference in the number of acicular grains between the interface zone and the bulk matrix (Z) is statistically significant for AR90/Z, SM72/Z, FM/Z, and DBM/Z interfaces, but not significant for TA/Z and AR78/Z. The role of the aggregates’ chemistry on the interfacial bonding and microstructure evolution is discussed.

Original language	English
Journal	Journal of the American Ceramic Society
DOIs	https://doi.org/10.1111/jace.70221
State	Accepted/In press - 2025

Funding

This manuscript has been coauthored by an employee of UT‐Battelle, LLC under Contract No. DE‐AC05‐00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non‐exclusive, paid‐up, irrevocable, world‐wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐public‐access‐plan ). The US Department of Energy (Advanced Manufacturing Office, AMO) funded this work (grant number: DE‐EE0001761). The authors are grateful to Dr. Andus Buhr (Almatis), Mr. Timothy McGrady and Ms. Veronica Vasquez (U.S. Zinc), Mr. Brett Ervin (Imerys), and Mr. Glenn McIntyre (HarbisonWalker International) for generous donation of raw materials. The technical discussion with Dr. Andus Buhr is highly appreciated. The authors are also grateful to Ms. Madeline D. Loveday and Mr. Max C. Modugno at Oak Ridge National Laboratory for meticulously reviewing the manuscript.

Keywords

bonding
calcium aluminate cement
gahnite
industrial aggregates
spinel

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10.1111/jace.70221

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@article{5af379a3053f4732ab1e5e132eb9b97d,

title = "Microstructure and bonding between calcium aluminate cement-containing gahnite–alumina matrix and refractory aggregates",

abstract = "Calcium aluminate cement enhances the thermomechanical properties of refractory castables through the formation of acicular calcium hexaluminate (CaO·6Al2O3), Ca2Mg2Al28O46 (CAM-I), and CaMg2Al16O27 (CAM-II) phases in MgO- or MgAl2O4-containing castables. The compatibility of CA6 with gahnite (ZnAl2O4), and acicular Ca2Zn2Al28O46 (CAZ-I) and CaZn2Al16O27 (CAZ-II) phases formation have been previously reported. In this work, the interaction between a CAC binder containing ZnAl2O4-Al2O3 matrix with commonly used refractory aggregates such as tabular alumina (TA), alumina-rich (AR90, AR78) and stoichiometric (SM72) MgAl2O4 spinels, and fused and dead-burned magnesia (FM, DBM, respectively) were investigated at 1650°C for 5 h. Microstructural analysis, using digital microscopy, scanning electron microscopy, and energy dispersive spectroscopy, revealed the formation of acicular CaZn0.18Al11.82O18.91, CAZ-I and CAZ-II grains, and strong interfacial bonding between the matrix and TA and spinel aggregates. FM and DBM were found to debond from the matrix. Thick interface layers were observed between the matrix and all the aggregates but TA. Null hypothesis significance testing (NHST) shows that the difference in the number of acicular grains between the interface zone and the bulk matrix (Z) is statistically significant for AR90/Z, SM72/Z, FM/Z, and DBM/Z interfaces, but not significant for TA/Z and AR78/Z. The role of the aggregates{\textquoteright} chemistry on the interfacial bonding and microstructure evolution is discussed.",

keywords = "bonding, calcium aluminate cement, gahnite, industrial aggregates, spinel",

author = "Ramteke, \{Rajat Durgesh\} and Hemrick, \{James G.\} and Mahapatra, \{Manoj K.\}",

note = "Publisher Copyright: {\textcopyright} 2025 The American Ceramic Society.",

year = "2025",

doi = "10.1111/jace.70221",

language = "English",

journal = "Journal of the American Ceramic Society",

issn = "0002-7820",

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TY - JOUR

T1 - Microstructure and bonding between calcium aluminate cement-containing gahnite–alumina matrix and refractory aggregates

AU - Ramteke, Rajat Durgesh

AU - Hemrick, James G.

AU - Mahapatra, Manoj K.

PY - 2025

Y1 - 2025

N2 - Calcium aluminate cement enhances the thermomechanical properties of refractory castables through the formation of acicular calcium hexaluminate (CaO·6Al2O3), Ca2Mg2Al28O46 (CAM-I), and CaMg2Al16O27 (CAM-II) phases in MgO- or MgAl2O4-containing castables. The compatibility of CA6 with gahnite (ZnAl2O4), and acicular Ca2Zn2Al28O46 (CAZ-I) and CaZn2Al16O27 (CAZ-II) phases formation have been previously reported. In this work, the interaction between a CAC binder containing ZnAl2O4-Al2O3 matrix with commonly used refractory aggregates such as tabular alumina (TA), alumina-rich (AR90, AR78) and stoichiometric (SM72) MgAl2O4 spinels, and fused and dead-burned magnesia (FM, DBM, respectively) were investigated at 1650°C for 5 h. Microstructural analysis, using digital microscopy, scanning electron microscopy, and energy dispersive spectroscopy, revealed the formation of acicular CaZn0.18Al11.82O18.91, CAZ-I and CAZ-II grains, and strong interfacial bonding between the matrix and TA and spinel aggregates. FM and DBM were found to debond from the matrix. Thick interface layers were observed between the matrix and all the aggregates but TA. Null hypothesis significance testing (NHST) shows that the difference in the number of acicular grains between the interface zone and the bulk matrix (Z) is statistically significant for AR90/Z, SM72/Z, FM/Z, and DBM/Z interfaces, but not significant for TA/Z and AR78/Z. The role of the aggregates’ chemistry on the interfacial bonding and microstructure evolution is discussed.

AB - Calcium aluminate cement enhances the thermomechanical properties of refractory castables through the formation of acicular calcium hexaluminate (CaO·6Al2O3), Ca2Mg2Al28O46 (CAM-I), and CaMg2Al16O27 (CAM-II) phases in MgO- or MgAl2O4-containing castables. The compatibility of CA6 with gahnite (ZnAl2O4), and acicular Ca2Zn2Al28O46 (CAZ-I) and CaZn2Al16O27 (CAZ-II) phases formation have been previously reported. In this work, the interaction between a CAC binder containing ZnAl2O4-Al2O3 matrix with commonly used refractory aggregates such as tabular alumina (TA), alumina-rich (AR90, AR78) and stoichiometric (SM72) MgAl2O4 spinels, and fused and dead-burned magnesia (FM, DBM, respectively) were investigated at 1650°C for 5 h. Microstructural analysis, using digital microscopy, scanning electron microscopy, and energy dispersive spectroscopy, revealed the formation of acicular CaZn0.18Al11.82O18.91, CAZ-I and CAZ-II grains, and strong interfacial bonding between the matrix and TA and spinel aggregates. FM and DBM were found to debond from the matrix. Thick interface layers were observed between the matrix and all the aggregates but TA. Null hypothesis significance testing (NHST) shows that the difference in the number of acicular grains between the interface zone and the bulk matrix (Z) is statistically significant for AR90/Z, SM72/Z, FM/Z, and DBM/Z interfaces, but not significant for TA/Z and AR78/Z. The role of the aggregates’ chemistry on the interfacial bonding and microstructure evolution is discussed.

KW - bonding

KW - calcium aluminate cement

KW - gahnite

KW - industrial aggregates

KW - spinel

UR - https://www.scopus.com/pages/publications/105015502247

U2 - 10.1111/jace.70221

DO - 10.1111/jace.70221

M3 - Article

AN - SCOPUS:105015502247

SN - 0002-7820

JO - Journal of the American Ceramic Society

JF - Journal of the American Ceramic Society

ER -

Microstructure and bonding between calcium aluminate cement-containing gahnite–alumina matrix and refractory aggregates

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