Effect of Combining the Aggregate Grading with Cementitious Composition on Mechanical Properties of Ultra-High Performance Concrete

Ultra-High Performance Concrete (UHPC) improves the bearing capacity as well as the durability of structural concrete. This study aims to investigate the constituents of UHPC in both phases: aggregate and cementitious materials. The proper ratio of the mixture was chosen based on combining an aggregate gradation of quartz sand and crushed stone. In addition, the compressive strength of the hardened cement paste was investigated to achieve the optimal ratio of silica powder and blast furnace slag. The combination of aggregate (quartz sand and crushed stone) and cement paste (cement, silica fume, silica powder, and blast furnace slag) showed ultra-high performance. The compressive strength of UHPC reached 135.74 MPa at 7 days, corresponding to 90% of 28 days’ strength (150.98 MPa). The results of the present study provide a new mixture-proportioning for UHPC with economic efficiency. Moreover, the use of slag enhances concrete performance and reduces the negative environmental impact.