Partial cement replacement by low-carbon-impact additions has the potential to reduce CO2 emissions. The aim of this study is the development of a ternary binder that includes ordinary Portland cement (OPC), ground granulated blast furnace slag (GGBS), and flash-calcined sediment (FCS). To upgrade dredged mineral material into FCS, a new heat treatment, i.e., flash calcination, was used. The used materials were physically, chemically, and mineralogically characterized. The mixture design method was used to optimize the design of the ternary blended binders. A model was developed and validated for the prediction of the 90-day compressive strength for mortars composed of OPC (C), GGBS (S), and FCS (F). Five mixes, reference RM (100% OPC), binary mix (50% OPC and 50% GGBS), and three ternary mixes with FCS rates of 10%, 15%, and 20% were characterized in fresh and hardened states. The results show that the incorporation of FCS reduced the workability of the mixes and increased their densities. Moreover, the initial setting time of the mix was delayed, and the heat of the hydration peak was decreased. The 90-day compressive strengths of the mix containing 10% FCS were higher than those of RM. In conclusion, the use of 10% FCS and 40% GGBS was an efficient substitute for 50% OPC.