An experimental investigation of the thermal spalling of polypropylene-fibered reactive powder concrete exposed to elevated temperatures

Polypropylene fibers are embedded to prevent reactive powder concrete (RPC) from spalling failure under high temperatures. This paper probes the influence of embedded fibers at various volumetric dosages on the thermomechanical properties of polypropylene-fibered reactive powder concrete (PPRPC) exposed to high temperatures up to 350 °C and on the spalling performance and characteristics up to 600 °C. The thermomechanical properties include the characteristic temperature for spalling, and residual strengths, such as the compressive strength, split tensile strength, and flexural tensile strength. A high-definition charge-coupled device camera and scanning electron microscope technology were employed to capture the spalling processes and to detect the microstructural changes in the materials with various fiber dosages. To understand and characterize the mechanism by which polypropylene fibers influence the thermal spalling of RPC, a numerical model to determine the moisture migration and vapor pressure transmission during spalling was developed in this paper. It showed that there was an optimal volumetric dosage of fibers to prevent PPRPC from explosive spalling. The relationships between the mechanical characteristics of PPRPC and the fiber dosages were derived based on experimental data.