The annual production of Portland cement, estimated at 3.4 billion tons in 2011, is responsible for about 7% of the total worldwide CO2-emission. To reduce this environmental impact it is important to use innovative technologies for the design of concrete structures and mixtures. In this paper, it is shown how particle packing technology can be used to reduce the amount of cement in concrete by concrete mixture optimization, resulting in more sustainable concrete. First, three different methods to determine the particle distribution of a mixture are presented; optimization curves, particle packing models and discrete element modelling. The advantage of using analytical particle packing models is presented based on relations between packing density, water demand and strength. Experiments on ecological concrete demonstrate how effective particle packing technology can be used to reduce the cement content in concrete. Three concrete mixtures with low cement content were developed and the compressive strength, tensile strength, modulus of elasticity, shrinkage, creep and electrical resistance was determined. By using particle packing technology in concrete mixture optimization, it is possible to design concrete in which the cement content is reduced by more than 50% and the CO2-emission of concrete is reduced by 25%.