Self-Compacting Concrete (SCC) is a special type of concrete recognized for placing in congested reinforced structures without any application of external vibration. Self compactibility can be determined by the properties of material constituents and the design of mix proportions. The absence of an approved code in India on mix design proportions and characteristics of material constituents to achieve compactibility in SCC has necessitated to determine a method for mix design of SCC. Though some researchers have carried out investigations to determine a proper mix design for producing SCC. In this investigation, the optimization of mix proportion design has been determined by adopting the proposed rational mix design method or Japanese method with necessary modifications in consonance with the guidelines of EFNARC. A suitable mix using the marginal aggregates was selected and numerous trial mixes (sixty-five) were carried out with the varying mix parameters like binder content, water-binder ratio, fine aggregate-coarse aggregate ratio, percentage of superplasticizer and viscosity modifying admixtures. The test results of this study are presented in this paper and a successful attempt has been made to determine the suitable mix design for producing SCC. © 2021, RILEM.