Process Design for a Production of Sustainable Materials from Post-Production Clay

Alkali activated cement (AAC) can be manufactured from industrial by-products to achieve goals of zero-waste production. We discuss in detail the AAC production process from (waste) post-production clay, which serves as the calcium-rich material. The effect of different parameters on the changes in properties of the final product, including morphology, phase formation, compressive strength, resistance to the high temperature, and long-term curing is presented. The drying and grinding of clay are required, even if both processes are energy-intensive; the reduction of particle size and the increase of specific surface area is crucial. Furthermore, calcination at 750 degrees C ensure approximately 20% higher compressive strength of final AAC in comparison to calcination performed at 700 degrees C. It resulted from the different ratio of phases: Calcite, mullite, quartz, gehlenite, and wollastonite in the final AAC. The type of activators (NaOH, NaOH:KOH mixtures, KOH) affected AAC mechanical properties, significantly. Sodium activators enabled obtaining higher values of strength. However, if KOH is required, the supplementation of initial materials with fly ash or metakaolin could improve the mechanical properties and durability of AAC, even c.a. 28%. The presented results confirm the possibility of recycling post-production clay from the Raciszyn II Jurassic limestone deposit.

Automated summary

Alkali activated cement (AAC) can be produced from industrial by-products to achieve zero-waste production goals. The production process involves various parameters affecting the properties of the final product, including morphology, phase formation, compressive strength, and resistance to high temperature. The choice of activators and supplementary materials can significantly influence the mechanical properties and durability of AAC.