Magnesium oxide-silicate (MgO-silicate) cement presents a promising alternative to ordinary Portland cement (OPC) with the potential to become CO2-neutral, depending on the raw materials and production technologies employed. However, the properties of these cements are not yet fully comparable to those of CaO-based cements. One of the main challenges with MgO-based binders is their high water demand and rapid loss of workability, which arise due to the stronger hydration reactions and more rigid hydration shells of Mg²⁺ ions compared to Ca²⁺ ions. To address these issues, the use of water-reducing agents, set retardants, and accelerators is crucial in maintaining the workability of MgO-based cement blends. Commercial admixtures like polycarboxylate ethers (PCEs) have shown some success in improving performance, but their effectiveness requires high dosages, which can lead to practical limitations. Moreover, research on the impact of various polymeric additives on the nucleation and growth of key magnesium phases, such as magnesium silicate hydrate (M-S-H), magnesium hydroxide (brucite), and magnesium carbonates, remains limited. This hinders the development and selection of the proper admixture(s) and the optimal dosages, which ensure the workability of MgO-based blends. In this context, novel additives offer significant potential for reducing the water demand of MgO-silicate cement. This project explores the effects of these additives on the formation of key magnesium phases, particularly M-S-H and brucite, using an automated experimental setup designed to induce homogeneous nucleation. The investigation also extends to heterogeneous phase formation, using MgO and silica fume as raw materials. The primary goal of this project is to identify suitable additive candidates that can enhance the performance and workability of MgO-silicate cement, making it a viable and attractive option for industrial applications.

Contact:

Annika Bastian, Cristina Ruiz Agudo

Publications:

1)     Ruiz-Agudo, C., & Bastian, A. (2024, November 11-12). Organic additive's influence on cement hydrates formation. In SUBLime Conference 2024 – Towards the next generation of sustainable masonry systems: Mortars, renders, plasters and other challenges. Funchal, Madeira, Portugal.

Links:

https://www.chemie.uni-konstanz.de/ruiz-agudo/research/projects/