Due to the vast quantities of concrete that are produced annually, the material represents substantial greenhouse gas (GHG) emissions, with clinker contributing the most significant portion. This paper presents an investigation aimed at reducing the clinker content required to achieve compressive strength while not detrimentally affecting workability, using particle packing modelling and limestone filler to replace clinker. The compaction interaction packing model (CIPM) and the modified Andreasen and Andersen curve (MAAC) were applied and integrated, the former for powder packing and the latter for fine and coarse aggregate packing. The CIPM was calibrated based on compaction effort applied experimentally, and predicted powder packing densities were validated experimentally. The integrated model was then applied to obtain optimized concrete mix designs with maximum packing density. Results showed that workability could be retained but compressive strength decreased relative to a reference mix. The binder efficiency index (kg binder/MPa/m3 concrete) showed very acceptable performance relative to the international literature, confirming that packing optimization was able to effect clinker reduction without detrimentally affecting compressive strength for strength classes < 50 MPa. There remains a need to maximize filler content in concrete mixtures and to better understand the fundamental influences of powder packing, to develop predictive processes that incorporate indicators of practical usability (such as water demand and expected workability) while maximising packing density.