In traditional mix design approaches for self-compacting concrete (SCC), the impact of the reactivity of the supplementary cementitious materials is based on the definition of the SCM type. This is problematic because the chemical composition, and therefore reactivity, of a given type of SCM is highly variable. As a result, mix designs developed with a specific SCM may not be transferable to other locations where the SCM chemical composition is not the same. To address this shortcomings, in this study, a unified approach to assess and model the fresh and hardened properties of self-compacting concrete containing supplementary cementitious materials is developed based on the application of the reactive moduli, which is formulated using the fraction of key oxides (SiO2, Al2O3, Fe2O3, CaO, MgO) in a unary or blended binder and the remaining key mix ingredients. An extensive test database containing the results of 1577 tests from 102 studies on fresh and hardened properties of SCCs, including slump flow, J-ring flow, initial and final setting time, T500 time, V-funnel time, segregation resistance index and H2/H1 ratio measured from L-box test together with the 28-day compressive strength is compiled to develop this approach. The predicted fresh and hardened properties of SCC correlate well with the experimental results. Having related the slump flow and the reactive moduli, the relationship between the slump flow and the other fresh and rheological properties of SCCs are also established. Examples of applications are presented to show how to proportion a SCC mix using the approach, and it is validated against test results not included in the calibration set. The approach presented in this study should serve as a means for the reliable and efficient proportioning of SCC a directly apply in engineering practices and can be applied directly in practice. (C) 2020 Elsevier Ltd. All rights reserved.