Development of an ettringite-based low carbon binder by promoting the nucleation and Ostwald ripening process

Abstract

A low-carbon binder with ettringite as the main binding phase is prepared at ambient temperature using waste gypsum and metallurgical slag as raw materials. The technical limits of slow setting and low early strength are caused by the insufficient ettringite formation. This is tackled by fine tuning the thermodynamic route of ettringite formation process using polyaluminium compound via promoting the nucleation and Ostwald ripening process of ettringite formation. The high positive charge polymeric Al species and numerous Al(OH)4- generated by the hydrolysis of polyaluminium compounds increase the oversaturation degree and enhance the driving force of the Ostwald ripening process of ettringite. The volume ratio of ettringite/C-(A)-S-H in hydration products is further increased remarkably, resulting in the reduction of setting time and the enhancement of compressive strength. The carbon emission of the non-calcined ettringite-based binders developed in this study is 71–87 kg CO2-e/t. The research provides theoretical support for the development and application of a novel ettringite-based low carbon binders.