Combining polypropylene and steel fiber to reduce spalling of reactive powder concrete

What is it about?

The objective of the study was to investigate the spalling phenomenon for reactive powder concrete matrix according to standard curve ASTM E119 with three different times of exposure (1, 1.5, 2) hours on the mechanical properties . Hybrid fiber polypropylene fiber (PPF) and steel fiber (SF) with volumetric dosage (0%, 1%), (0.5%, 0.75%), (1%, 0.5%), (1.5%, 0.25%) and (2%, 0%) respectively were used.

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Why is it important?

One of the most important problems of RPC is that when subjected to fire at high temperatures, Degradations such as loss of strength and elastic module, cracking which led to concrete spalling and collapse. Compared with NSC and HSC, RPC have dense microstructure, which make more vulnerable to spalling due to prevent water vapor from escaping and lead to high pore pressure. Compared with glass fiber and carbon fiber (PPF) have low melting point ,which melt at a relatively low temperature of approximately 160-170 C0 in the RPC mix and produce selectively tiny pores throw the RPC matrix. This pores allow diffusion of the high vapor pressure generated in an RPC structure