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

Journal Article · Wed Jul 27 00:00:00 EDT 2016 · Thermochimica Acta

DOI:https://doi.org/10.1016/j.tca.2016.07.021· OSTI ID:1356987

Engbrecht, Dick C.  ^[1]; Hirschfeld, Deidre A. ^[2]

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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)

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.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); New Mexico Inst. of Mining and Technology, Socorro, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1356987
• Alternate ID(s): OSTI ID: 1396794
• Report Number(s): SAND2016-12607J; PII: S0040603116301952
• Journal Information: Thermochimica Acta, Vol. 639; ISSN 0040-6031
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Gypsum
Anhydrite
Differential thermal analysis/thermogravimetric analysis
X-ray diffraction