The effect of Silica Fume and Fly Ash on the Properties of Reactive Powder Concrete and its comparison with High Strength Concrete

Reactive powder concrete (RPC) is a type of high-performance concrete. RPC eliminates the use of coarse aggregates in the mixture to increase compactness. RPC is composed by materials such as Portland cement (OPC), quartz sand, quartz powder, supplementary cementitious materials, water, superplasticizer, fiber (optional). This research consists of two basic parts. The first part investigates the effects of many parameters on the fresh and mechanical properties of locally cast (RPC). The effective parameters are volume of binder content ratio, water-binder ratio, the type of supplementary cementitious material (silica fume (SF) and fly ash (FA)), and, also, their ratio. These parameters were examined experimentally to evaluate their effect on workability, compressive, tensile, and flexural strength. The second part was concerned with comparing the effects of both mentioned supplementary cementitious materials on (RPC) and high-strength concrete (HSC). The results indicate an obvious decrease in RPC workability and an increase in strength by replacing part of the cement with silica fume. RPC can achieve high strength when the volume of binder content is 60% and silica fume replaces up to 20% of cementitious materials. The results also revealed that RPC workability is improved when a part cementitious material is substituting by fly ash. However, excessive replacement of cement with fly ash leads to a reduction in strength. Moreover, the results showed that substituting 10% of cementitious materials with fly ash and silica fume improved the compressive strength of RPC by 43% and 36%, respectively, higher than that of HSC.