Waste-Based Porous One-Part Inorganic Polymers for Building Applications

Growing concerns over greenhouse gas emissions have intensified the search for low-carbon alternatives in the construction sector, which is strongly dependent on Portland cement production, responsible for approximately 0.5–0.7 tons of CO₂ per ton of cement produced. In this context, alkali-activated materials have emerged as promising sustainable alternatives to conventional binders. Among them, one-part systems offer additional practical advantages due to their simplified handling and safer production process, as they do not require the handling of highly alkaline solutions. However, porous formulations of these materials remain comparatively underexplored.

Ground granulated blast furnace slag (GGBS), a by-product of the iron industry, was used as the sole solid precursor. Sodium metasilicate (SM) served as the solid alkaline activator, while hydrogen peroxide (HP) acted as a foaming agent. A constant liquid-to-binder ratio of 0.36 was maintained across all formulations. The influence of varying HP (1, 2.5, and 5 wt.% of the liquid phase) and SM (0.25, 0.5, and 0.75 wt.% of the binder) contents on the hardened properties of porous one-part inorganic polymers was investigated.

The produced porous materials exhibited variable compressive strength, low apparent density (0.76–1.20 g/cm³), and low thermal conductivity (0.130–0.176 W/m.K). Moreover, all formulations demonstrated good indoor moisture buffering capacity (MBV > 1.0 g/m² Δ%RH), as classified by the Nordtest protocol.

The results confirm the feasibility of tailoring the properties of waste-based one-part inorganic polymers via targeted adjustment of HP and SM contents, enabling performance optimization for specific application requirements. These materials present a promising pathway toward the development of sustainable and energy-efficient solutions for non-structural building applications.

Acknowledgements

This work was developed within the scope of the project CICECO Aveiro Institute of Materials, UID/50011/2025 (DOI 10.54499/UID/50011/2025) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through the FCT/MCTES (PIDDAC).