Effect of the Type of Silica Fume and Filler on Mechanical Properties of Ultra High Performance Concrete

The large quantities of expensive materials such as steel fiber, silica fume, filler and superplasticizer required in the composition of Ultra-High Performance Concrete (UHPC) make its fabrication cost significantly higher than ordinary concrete. This study evaluates the effect of the type of silica fume and filler on mechanical properties of UHPC. The evaluation shows that the use of Zr silica powder instead of common silica fume improves significantly the fluidity of UHPC without loss of the strength and enables to reduce the amount of superplasticizer by maximum 70%. Moreover, the evaluation of the effect of the type and size of the filler reveals that modifying the size of the filler from 2 μm to 4 μm enhances the fluidity without strength loss and that the use of cement kiln dust (CKD) and limestone powder can achieve UHPC with compressive strength higher than 150 MPa. These results show that the use of the materials such as Zr silica powder, CKD and limestone powder can help to fabricate more economic UHPC.