Mechanical properties and microstructure of reactive powder concrete using ternary pozzolanic materials at elevated temperature

To provide fundamental data on developing an economical and practical Reactive Powder Concrete (RPC), a modified RPC was made in this study. This modified RPC significantly reduced the content of cement and silica fume compared to the conventional RPC mixture by the combination of ternary pozzolanic materials (silica fume, blast furnace slag, and fly ash). A series of fire tests was conducted on modified RPC specimens, and their mechanical properties and microstructures were investigated under high temperatures. The results clearly showed that the mechanical performance of the modified RPC under high temperatures was superior to that of the conventional RPC mixture (SF25 type) with only silica fume (SF/C = 25%). The residual compressive, flexural, and tensile strength of the modified RPC after exposure to 1000oC resulted in more than 62 MPa, 8 MPa, and 4 MPa, respectively. The range of 400~800℃ may be regarded as the critical temperature range for the strength loss of the modified RPC, which led to significant changes in the microstructure of the RPC matrix, as shown in the results of the pore structure analysis and XRay Diffraction (XRD).