Portland cement manufacturing process consumes large amount of natural resources and generates approximately 5% of global CO2 emissions. Consequently, alternative approaches for CO2 reduction are an important cement industry focus. The present project revisits lime-­‐pozzolan systems, as a modern approach to sustainable cement technology. The idea of the partial calcination of limestone to produce core-­‐shell like lime for blending with pozzolan is proposed. The partial calcination of limestone has been studied in an experimental fluidised bed reactor. The calcination conditions, including residence time, temperature, air flow rate and particle size of limestone, have a significant influence on the kinetics of the decomposition reaction and subsequent properties of the partially calcined limestone. The porous CaO shell on a limestone particle can provide the same reactivity as a fully calcined particle except that only the activated portion is available for reaction, the unreacted core remaining as a micro-­‐aggregate in matrices of C-­‐S-­‐H. The performance test demonstrates that a blend of partially calcined limestone and rice husk ash produced in the FBR provides sufficient compressive strength, workability, water retentivity and durability for use as plastering and masonry mortar. The coated Ca(OH)2 shell on a limestone particle exhibits an advantage in the fresh mortar properties such as workability and water retention. The sustainability assessment proves that CO2 emissions and the thermal energy consumption for the production of partially calcined limestone – pozzolan mortar is lower than those of conventional mortar.