Calcium Alginate-Glycerol Gel as an Organic Matrix to Induce the Mineralisation and Growth of Calcium Carbonate as a New Eco-Friendly Binder Composite

Natural carbonated composites are formed by calcium carbonate crystals embedded within an organic matrix that the living organism excretes. In this study, a solvent made with sodium alginate, glycerol and sodium hydroxide was used to promote the mineralisation of biomimetic calcium carbonate. Carbon dioxide was captured and stored as a carbonate binder composite, and the cementitious mechanism toward sand particles was revealed. The binder composite comprises amorphous calcium carbonate, calcium alginate-glycerol gel and calcite. Organic additives were crucial to promote the mineralisation of the most stable calcium carbonate polymorph, calcite. The final calcite crystals presented a peanut-like shape, detached from a structured sea urchin-like particle. An estimated 0.15 tonne of carbon dioxide could be permanently stored in 1 tonne of the biomimetic calcium carbonate and sand composite. The composite block presented a compressive strength and elastic modulus of 0.85 and 21.3 MPa, respectively. It is believed that the cementitious mechanism of the carbonate binder composite is formed through the crystallisation of amorphous calcium carbonate (ACC) embedded inside a three-dimensional organic gel enriched with calcium ions into calcite. Hence, calcium carbonate mineralisation mediated by sodium alginate and glycerol introduces new possibilities to create a novel, more sustainable, environmentally friendly binder material.