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Materials 2017, 10(8), 958; https://doi.org/10.3390/ma10080958

Production of Synthetic Phosphoanhydrite and Its Use as a Binder in Self-Leveling Underlayments (SLU)

1
Post-Graduate Program in Civil Engineering, Federal University of Santa Catarina, CEP 88040-900 Florianópolis, SC, Brazil
2
Department of Civil Engineering, Federal University of Santa Catarina, CEP 88040-900 Florianópolis, SC, Brazil
*
Author to whom correspondence should be addressed.
Received: 7 June 2017 / Revised: 30 June 2017 / Accepted: 8 August 2017 / Published: 17 August 2017
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

An experimental study was conducted to investigate the potential use of phosphogypsum (PG) to produce self-leveling underlayments. The study was designed in two stages. Initially a phosphoanhydrite (PA) was produced by heating phosphogypsum at temperatures of 350 °C, 450 °C, 550 °C, and 650 °C. Two periods of heating were applied (2 and 4 h). The formation of anhydrite was determined by thermogravimetric analysis (DTA-TG) and confirmed by X-ray diffraction (XRD). The results show that anhydrite II was obtained at temperatures above 450 °C, and at higher calcination temperatures the PA solubility was lower. In the second stage of this research, the PA was used in self-leveling underlayments as the main binder in the ternary system comprised of calcium sulfate, calcium aluminate cement, and Portland cement. Self-leveling mortar screeds produced using PA (550 °C/4 h) and PA (650 °C/4 h) showed the best performance in terms of mechanical strength and no degradation was observed after immersion and immersion-drying tests. The formation of ettringite, identified by scanning electron microscopy (SEM), may have contributed to these results. Morphological changes were studied using the scanning electron microscopy (SEM) technique. View Full-Text
Keywords: calcium sulfate; phosphogypsum; anhydrite; self-leveling mortars calcium sulfate; phosphogypsum; anhydrite; self-leveling mortars
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Schaefer, C.O.; Cheriaf, M.; Rocha, J.C. Production of Synthetic Phosphoanhydrite and Its Use as a Binder in Self-Leveling Underlayments (SLU). Materials 2017, 10, 958.

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