Thermal stability and high-temperature behavior of the natural borate colemanite: An aggregate in radiation-shielding concretes. (10th April 2019)

• Record Type: Journal Article
• Authors: Lotti, Paolo; Comboni, Davide; Gigli, Lara; Carlucci, Lucia; Mossini, Eros; Macerata, Elena; Mariani, Mario; Gatta, G. Diego
• Is Part Of: Construction & building materials. Volume 203(2019)
• Page Start: 679
• Page End: 686
• Publication Date: 2019-04-10
• Subjects: Colemanite -- Boron -- Neutron radiation shielding concretes -- High temperature -- Dehydration -- Amorphization -- Thermal expansion coefficient -- Synchrotron X-ray diffraction; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2019.01.123
• Languages: English
• ISSNs: 0950-0618

Abstract

Graphical abstract: Highlights: Colemanite can be used as an aggregate in neutron radiation-shielding concretes. We have investigated its high- T behavior by means of DSC, TG and XRD analyses. The loss of structural H2 O unambiguously occurs at least from ∼240 °C. At T > 325 °C an irreversible amorphization towards an anhydrous form occurs. The amorphization process is triggered in the very early stages of dehydration. Abstract: Colemanite is a natural borate that can be used as an aggregate in neutron-radiation shielding concretes. In this study, we report its thermal behavior, up to 500 °C, by describing: 1) its dehydration mechanisms and 2) its thermo-elastic parameters. The thermal expansion of colemanite is significantly anisotropic. The refined volume thermal expansion coefficient at ambient conditions is: α V 0 = 4.50(10)·10 −5 K −1 . The loss of structural H2 O occurs at least from ∼240 °C, and at T > 325 °C an irreversible amorphization occurs, followed by a complete dehydration. The potential implications on the use of colemanite as concrete-aggregate are discussed.