The role of flame retardants in cement mortars exposed at elevated temperatures

摘要

The performance of building materials at extreme temperatures is a significant parameter taken into account, in order to apply fire safety criteria in constructions. In this study, various flame retardants (aluminum tri-hydroxide/Al(OH)(3), magnesium hydroxide/Mg(OH)(2), nano-clay) were used as additives in cement mortars, in order to evaluate their impact at high temperatures. The mortar specimens were exposed at 200, 400, 600, 800 and 1000 degrees C and their physico-mechanical characteristics (mass and volume loss, porosity, water absorption, specific gravity, dynamic modulus of elasticity, flexural- compressive strength) were studied. Additionally, their mineralogical (X-Ray diffraction), thermal (Thermogravimetric/Differential Thermogravimetric analysis (TG-DTG), Differential Scanning Calorimetry (DSC)) and microstructure (scanning electron microscopy) properties were recorded. The results indicated the positive role of additives in the mortar matrix, especially when they were combined. In particular, the combination of nano-clay with Al(OH)(3) or Mg(OH)(2) increased the resistance to flexure up to 1000 degrees C, while the mass and volume loss was also retained. The beneficial role of the Al(OH)(3) and Mg(OH)(2) addition in cement mortars exposed up to 600 degrees C, was documented in the experimental results. (C) 2020 Elsevier Ltd. All rights reserved.