One-part geopolymer-like binders with calcium-based solid alkaline activators and metakaolin

The need to reduce greenhouse gas emissions has promoted the development of sustainable materials for the building industry to replace ordinary Portland cement (OPC). This work focuses on the development of one-part geopolymer-like binders using calcium-based solid alkaline activators and metakaolin. The alkaline activator was prepared by mixing Ca(OH)2 or CaO and Na-silicate or K-silicate, all in powders form. XRD, FTIR, TGA/DTG and solid-state NMR analyses show the coexistence of both geopolymer gel and hydrated aluminosilicates. Microscopical investigations show that the morphology of the binders is heterogeneous with micrometric agglomerates. TEM reveals that the binders are characterized by agglomerates of nanoparticles, with abundant amorphous material and rare crystalline phases. The mechanical properties demonstrate the potential of this product as an eco-friendly alternative to OPC. The use of powdered alkaline activators and the production process followed make the product suitable for the building industry to be used on construction sites.