The processes focused on stone cutting generate a large volume of waste. Small size waste, silt/clay, is not used and goes to landfill. However, the composition of these wastes makes them useful for adding to cements and for use in construction. In the present paper, 10% Ordinary Portland cement is replaced by 10% waste from granite sawmill, which is studied to obtain sustainable ecological cement. This replacement provides advantages from the morphological and chemical point of view at the cements. The waste has a particle size that does not exceed 15 µm and that when replacing in the cement, after the hydration reaction, generates structures where Calcium Silicate Hydrate (C-S-H) gels and double layered hydroxide compounds (LDH) are reaction products formed in high concentration. These products develop stable phases in the structures over long time periods such one year, which was the time frame used in this study.

Numerous waste streams can be employed in different cement production processes, and the inclusion of pozzolans will, moreover, permit the manufacture of concrete with improved hydraulic properties. Pozzolanic materials can be added to Ordinary Portland Cement (OPC) in the range of 10%–20% by mass of cement. One such example is the phyllosilicate kaolinite (K), and its calcined derivative metakaolin (MK), incorporated in international cement manufacturing standards, due to its high reactivity and utility as a pozzolan. In the present paper, discarded ballast classed as Construction and Demolition Waste (C&DW) is reused as a pozzolanic material. Various techniques are used to characterize its chemical, mineralogical, and morphological properties, alongside its mechanical properties, such as compressive and flexural strength. Discarded ballast in substitution of cement at levels of 10% and 20% produced type II or IV pozzolanic cements that yielded satisfactory test results.

The cement industry is one of the world’s largest CO₂ emitters. The need to minimize these emissions, and assimilate by substitution and different types of waste, are challenges faced in the European Union. The use of granite sawmill from the ornamental stone industry allows for the manufacturing of pozzolanic cements, in which 10% and 20% of ordinary Portland cement (OPC) has been replaced by waste. In the present paper, properties of cements and mortars have been tested (when fresh and once set), such as workability, setting, retraction, mechanical resistance to bending and compression, elastic modulus to compression, creep, retraction, and durability. In all cases and substitution proportions, the results have been as satisfactory as those achieved with OPC, even better, allowing a second life to the waste, and participating in the principles of the circular economy. Bot substitutions are very resistant and have great durability for the gelifraction processes from the new green cements. Using this waste—granite sawmill—its volume is minimized and transfer to a landfill is avoided.