The influence of fiber, aggregate and cementitious materials on the mechanical properties of ultra-high content steel fiber reinforced reactive powder concrete

This study investigates the effects of fiber, aggregate and cementitious materials on the mechanical properties of ultra-high content steel fiber reinforced reactive powder concrete (RPC) under autoclaved curing condition. The results showed that the compressive strength of the specimen with 9% chopped steel fibers hit 303.4 MPa, which was 184.7% higher than that of the specimen without steel fibers. An increase in compressive strength of 233.1% was observed for mixtures incorporating 9% of the long steel fibers, compared to that of the mixture without steel fibers, reaching a maximum value of 355.0 MPa. Increasing the dosage of short steel fibers improved the compressive strength, while increasing the dosage of long steel fibers enhanced the flexural strength. Substituting quartz sand with fine ceramic microspheres as aggregate had been found to enhance the compressive strength of RPC, but resulted in a reduction in flexural strength. Conversely, the SEM image shows that the incorporation of quartz powder with smaller particle size as cementitious material will make the RPC denser and can significantly improve the flexural strength. The research results can provide valuable references for the subsequent optimization of the compressive and flexural strength of RPC with ultra-high content steel fibers.