<![CDATA[The utilization of high-performance fast-track concrete has become an important solution for improving efficiency and accelerating construction schedules in modern infrastructure projects. This study aimed to determine the optimum combination of Rice Husk Ash (RHA) as a pozzolanic material with the addition of a superplasticizer (Viscocrete 1050 HE) and an accelerator (Sika Rapid 505) in high-strength concrete targeting a compressive strength of 60 MPa. Cement was partially substituted with RHA at variations of 0%, 5%, 10%, and 15% by weight of the total binder. The evaluation included workability and hardened concrete properties, namely compressive, flexural, and splitting tensile strengths, tested at curing ages of 1, 2, 3, and 28 days. The results showed that increasing the RHA content beyond 5% reduced workability due to the high specific surface area of RHA particles. At 1 day, the cement dilution effect reduced compressive strength from 30.3 MPa in the control mix to 25.3 MPa at 15% RHA substitution. However, the use of Sika Rapid 505 successfully mitigated this reduction and maintained early-strength development. At 28 days, the optimum performance was achieved with 5% RHA substitution, producing a compressive strength of 52.2 MPa and a flexural strength of 7.1 MPa, while the highest splitting tensile strength of 4.3 MPa was obtained at 10% RHA. Overall, the combination of 5% RHA, Viscocrete 1050 HE, and Sika Rapid 505 demonstrated the best synergistic performance in maintaining fresh concrete properties and enhancing the mechanical performance of high-strength fast-track concrete.]]>
