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Title: Thermal analysis of calcium sulfate dihydrate sources used to manufacture gypsum wallboard

Abstract

Gypsum wallboard has been used for over 100 years as a barrier to the spread of fire in residential and commercial structures. The gypsum molecule, CaSO 4·2H 2O, provides two crystalline waters that are released upon heating providing an endothermic effect. Manufacturers have recognized that the source of the gypsum ore is a factor that affects all aspects of its performance; thus, it is hypothesized that the impurities present in the gypsum ore are the causes of the performance differences. Differential Thermal Analysis/Thermogravimetric Analysis (DTA/TGA) and X-ray Diffraction (XRD) were used in this paper to compare and characterize samples of gypsum ore representing sources of natural, synthetic from a Flue Gas Desulfurization process (FGD) and blends thereof. The hemihydrate phase of representative natural, FGD, and reagent grade calcium sulfate were rehydrated with distilled water and evaluated by DTA/TGA. Analysis of the data shows distinct areas of similarity separated by the conversion to anhydrite ~250 °C. Compositional reconstructions based on DTA/TGA and XRD data were compared and although, the results were comparable, the DTA/TGA suggests thermally active compounds that were not detected by XRD. Anhydrite, silica and halite were reported by XRD but were not thermally reactive in the temperature rangemore » evaluated by DTA/TGA (ambient to 1050 °C). Finally, the presence of carbonate compounds (e.g., calcite and dolomite) were indicated by XRD and estimated from the thermal decomposition reaction ~700 °C.« less

Authors:
ORCiD logo [1];  [2]
  1. New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. of Materials Science and Engineering
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); New Mexico Inst. of Mining and Technology, Socorro, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1356987
Report Number(s):
SAND2016-12607J
Journal ID: ISSN 0040-6031; PII: S0040603116301952
Grant/Contract Number:
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Thermochimica Acta
Additional Journal Information:
Journal Volume: 639; Journal ID: ISSN 0040-6031
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Gypsum; Anhydrite; Differential thermal analysis/thermogravimetric analysis; X-ray diffraction

Citation Formats

Engbrecht, Dick C., and Hirschfeld, Deidre A. Thermal analysis of calcium sulfate dihydrate sources used to manufacture gypsum wallboard. United States: N. p., 2016. Web. doi:10.1016/j.tca.2016.07.021.
Engbrecht, Dick C., & Hirschfeld, Deidre A. Thermal analysis of calcium sulfate dihydrate sources used to manufacture gypsum wallboard. United States. doi:10.1016/j.tca.2016.07.021.
Engbrecht, Dick C., and Hirschfeld, Deidre A. 2016. "Thermal analysis of calcium sulfate dihydrate sources used to manufacture gypsum wallboard". United States. doi:10.1016/j.tca.2016.07.021. https://www.osti.gov/servlets/purl/1356987.
@article{osti_1356987,
title = {Thermal analysis of calcium sulfate dihydrate sources used to manufacture gypsum wallboard},
author = {Engbrecht, Dick C. and Hirschfeld, Deidre A.},
abstractNote = {Gypsum wallboard has been used for over 100 years as a barrier to the spread of fire in residential and commercial structures. The gypsum molecule, CaSO4·2H2O, provides two crystalline waters that are released upon heating providing an endothermic effect. Manufacturers have recognized that the source of the gypsum ore is a factor that affects all aspects of its performance; thus, it is hypothesized that the impurities present in the gypsum ore are the causes of the performance differences. Differential Thermal Analysis/Thermogravimetric Analysis (DTA/TGA) and X-ray Diffraction (XRD) were used in this paper to compare and characterize samples of gypsum ore representing sources of natural, synthetic from a Flue Gas Desulfurization process (FGD) and blends thereof. The hemihydrate phase of representative natural, FGD, and reagent grade calcium sulfate were rehydrated with distilled water and evaluated by DTA/TGA. Analysis of the data shows distinct areas of similarity separated by the conversion to anhydrite ~250 °C. Compositional reconstructions based on DTA/TGA and XRD data were compared and although, the results were comparable, the DTA/TGA suggests thermally active compounds that were not detected by XRD. Anhydrite, silica and halite were reported by XRD but were not thermally reactive in the temperature range evaluated by DTA/TGA (ambient to 1050 °C). Finally, the presence of carbonate compounds (e.g., calcite and dolomite) were indicated by XRD and estimated from the thermal decomposition reaction ~700 °C.},
doi = {10.1016/j.tca.2016.07.021},
journal = {Thermochimica Acta},
number = ,
volume = 639,
place = {United States},
year = 2016,
month = 7
}

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  • United States Gypsum Company (USGC) has developed specifications and guidelines covering the chemical and physical aspects of synthetic gypsum to help predict end use acceptability in wallboard manufacture. These guidelines are based in part on past experiences with natural and synthetic gypsum. Similarly, most wallboard manufacturers in North America have developed their own guidelines based in part on its unique history and particular experiences with synthetic gypsum. While there are similarities between manufacturers` guidelines, differences do exist. This paper discusses the importance of selected parameters contained in the FGD gypsum guidelines. In most cases, the parameters are equally relevant tomore » other synthetic gypsums and the naturally occurring gypsum mineral as well.« less
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  • It was established that in the process of isolation of calcium sulfate dihydrate, plutonium(IV) is coprecipitated with the formation of anomalous mixed crystals. It was shown that the interfacial distribution of plutonium(IV) obeys a logarithmic distribution law with coefficient of crystallization (lambda) equal to approximately 0.5 when the concentration of the microcomponent is varied from 6.3 x 10/sup -9/ to 1.8 x 10/sup -4/ M. When the plutonium concentration was further increased to 8.9 x 10/sup -4/ M, a decrease in the coefficient of crystallization was observed under conditions of the greatest acidity of the medium. It was established bymore » thermographic analysis that freshly formed deposits of calcium sulfate dihydrate contain a metastable ..cap alpha.. modification, the lifetime of which is approximately five days. It was shown that the presence of electrolytes (NaCl, KCl, and NaNO/sub 3/) in the solutions promotes the formation of the alpha form of gypsum in the process of isolation of calcium sulfate and an increase in the lifetime of the ..cap alpha.. phase. The hypothesis that the trapping of plutonium(IV) is due to the formation of a metastable ..cap alpha.. phase of gypsum was advanced and confirmed.« less