Fire resistance of light wood frame walls sheathed with innovative gypsum-particle composite: Experimental investigations

Gypsum board (GB) is used as a fire-resistant component of light wood frame (LWF) walls for its excellent fire resistance, but cracking and separation cause LWF failure due to water release at high temperature. In this study, eight mesoscale LWF walls were tested to determine the effects of an innovative gypsum-particle composite (IGP) on fire resistance, according to the ISO 834 standard. Three LWF walls were burned until failure for determination of fire endurance. Five LWF walls were heated for 0, 20, and 30 min during a standard fire and followed by lateral load resistance testing. Scanning electron microscopy was used to analyze microscopic changes of crystal morphology in GB and IGP after various periods in fire. The results indicated that the temperature in walls sheathed with IGP or double-layer GB consistently increased more slowly than single-layer GB during fire testing. The fire endurance of IGP-wall was 50.9 min, which was 12.9% higher compared to GB-wall and met the demands of a non-load-bearing exterior wall and partition wall on both sides of an evacuation route in timber structures. The fire endurance of the wall sheathed with two-layer GB was 55.7 min. The length of needle-like crystals in GB tended to be shorter in fire tests due to the release of chemically bound water, leading to cracks at high temperature. The residual morphology of IGP exhibited as intact after the same duration fire tests, compared to GB. The residual maximum load (P_peak), elastic shear stiffness (K_e), and ductility (D) of IGP-wall heated for 20 min during standard fire were reduced by 10, 35, and 18%, but were also 6, 75, and 53% more compared to GB-wall. Under a 30 min duration exposure, the P_peak, K_e, and D of IGP-wall were 1.15, 1.74, and 1.48 times that of GB-wall, respectively. IGP was capable of beneficially substituting for GB in LWF wall.