Experimental study on high-temperature resistance of alkali-activated slag concrete block masonry

The use of blast furnace slag improves resource utilization and supports the achievement of sustainable development goals. The use of alkali-activated slag cementitious material (AASCM) provides a new direction for improving the fire resistance of masonry structures. The masonry investigated in this study was alkali-activated slag crushed aggregate concrete masonry (ASCCM) in which aggregates of blocks and mortars were crushed and screened using AASCM paste specimens. The compression behavior of 12 specimens during and after exposure to high temperatures, specifically 300, 500, 600, 700, 800, and 900°C was investigated. The specimens were maintained under the target temperature for 2 h. The compressive strength and axial deformation of the specimen were recorded. The compressive strength losses during exposure to 300, 500, 600, 700, 800, and 900°C are 15.9, 20.3, 38.3, 43.9, 63.3 and 73.8%, respectively. The compressive strength losses after exposure to 300, 500, 600, 700, 800, and 900°C are 10.6, 15.8, 34.0, 37.2, 58.6 and 72.2%, respectively. The rate of loss in elastic modulus is greater than that in compressive strength. During exposure to 300, 500, 600, 700, 800, and 900°C, the loss rates of elastic modulus are 56.5, 74.4, 83.3, 86.3, 92.9 and 93.9%, respectively. After exposure to 300, 500, 600, 700, 800, and 900°C, the loss rates of elastic modulus are 49.6, 67.3, 77.5, 82.0, 90.7 and 94.5%, respectively. The peak compressive strain values are 9.9 and 11.1 times that at room temperature. Equations for calculating the compressive strength, elastic modulus, peak compressive strain, and ascending section curve of the stress–strain relationship with temperature were derived. The research results provide a new choice for high temperature resistant masonry materials, and provide theoretical basis and data support for the application of AASCM in masonry structures in high-temperature environments.