Experimental investigation of behavior of reinforced high-strength concrete walls under standard fire

Reinforced high-strength concrete (RHSC) walls are widely used in high-rise buildings. A greater likelihood of spalling and smaller member sizes poses a high risk to structural fire safety. In this study, five RHSC wall specimens with various concrete strengths, axial load levels, thicknesses and reinforcement configurations were tested under one-sided bottom-up standard fire. The timedependent thermal and deformation evolutions and the spalling characteristics were measured and analyzed. The results indicate severe spalling of RHSC walls which can lead to catastrophically early buckling failure at about half an hour of fire. Distinguishing spalling types highly related to concrete strength are identified, and the axial load is revealed to have significantly twofold effects in increasing spalling which will be much more critical for RHSC walls with higher strength's concrete. Besides, it is discovered that reduction of wall thickness leads to considerable decrease of spalling and can effectively increase the fire resistance of thin RHSC walls with relatively lower concrete strength. The spalling-eliminating effect of flexural cracks will become limited in thicker walls or when concrete is of higher strength. Finally, it is found that applying double-layer reinforcement configuration has little effect in reducing spalling but can still significantly increase the fire resistance of RHSC walls.