Elevated temperature thermal properties of advanced materials used in LSF systems

Abstract

Lightweight cold-formed steel (CFS) construction solutions are increasingly adopted in low and mid-rise buildings. Many different materials are used to construct CFS wall systems, without a full understanding of their thermal properties. For many of these materials, only ambient temperature thermal properties are available from their manufacturers. This creates difficulty in classifying the materials for use at elevated temperatures. In this study, a series of elevated temperature thermal property tests to measure specific heat, thermal conductivity, and mass loss was conducted for a range building materials from wallboards, insulation, and phase-change materials (PCMs), used in Australia and several other countries. Simultaneous Thermal Analyser and Laser Flash Apparatus were used to determine the elevated temperature thermal properties of the selected materials, gypsum plasterboard, PCM incorporated gypsum plasterboard, magnesium sulphate board, fibre cement board, cellulose insulation, vacuum insulation panel, microencapsulated paraffin PCM, and bio-based PCM. Their elevated temperature thermal properties are presented in this article, which also includes analyses of their chemical composition and associated chemical reactions at elevated temperatures. These results can be used in the selection of suitable energyefficient and fire-resistive materials, and in heat transfer modeling to identify wall configurations with increased fire resistance and energy efficiency.

Development of Lightweight Steel Framed Construction Systems for Nearly-Zero Energy Buildings

“…Table 3. Thermophysical properties of commonly used non-metallic sheathing materials for LSF [38,40,41].…”

“…The first reaction leads to the decomposition of gypsum into calcium sulphate hemihydrate at temperatures between 80 and 120 • C, while the second reaction decomposes the calcium sulphate hemihydrate into calcium sulphate anhydrite at temperatures between 200 and 240 • C, which affects the specific heat change [50]. To further increase the fire resistance of GBs, various additives such as cellulose fibers and fly ash can be added [41]. The diagram in Figure 3 represents the change in specific heat values of GBs at different temperatures compared to other non-metallic sheathing boards, showing the endothermic reactions mentioned above.…”

“…A variant of MgO boards is magnesium sulphate boards which have a similar chemical composition to magnesium oxide boards. They are composed of magnesium oxide (about 55%), sulphate (about 25%), and glass fibers (about 18%) [41]. Replacement of MgCl2 in basic magnesium oxide boards with MgSO 4 eliminates the corrosive effect of chlorides [41].…”

“…They are composed of magnesium oxide (about 55%), sulphate (about 25%), and glass fibers (about 18%) [41]. Replacement of MgCl2 in basic magnesium oxide boards with MgSO 4 eliminates the corrosive effect of chlorides [41]. Gnanachelvam et al [41] studied the thermal properties of this type of board at elevated temperatures and found that the fire behavior of magnesium sulphate boards was slightly better than that of magnesium oxide boards, but the same rapid cracking and mass loss occurred.…”

“…Replacement of MgCl2 in basic magnesium oxide boards with MgSO 4 eliminates the corrosive effect of chlorides [41]. Gnanachelvam et al [41] studied the thermal properties of this type of board at elevated temperatures and found that the fire behavior of magnesium sulphate boards was slightly better than that of magnesium oxide boards, but the same rapid cracking and mass loss occurred. Since magnesium oxide and magnesium sulphate boards are similar, their chemical decomposition at elevated temperatures is identical; the process is shown in Figure 4.…”