Sustainable cement-based composites: the effect of blended cements and CO2-cured ladle slag on electrical conductivity of silicate composites

The cement industry is one of the largest environmental polluters, responsible for approximately 7–8% of global CO2 emissions. The search for more sustainable alternative binders and innovative composites is therefore becoming a key direction in the development of building materials. This paper investigates the effect of cement type and CO2 cured alternative binder on the resistivity of a silicate composite with carbon-based filler. The amount of electrically conductive filler was kept below the percolation threshold to observe changes in the electrical properties of the material due to chemical and microstructural modifications, and for the same reason the porosity of the material was maintained. The alternative binder was a 50/50 mixture of cement and grounded ladle slag, cured in a controlled CO2 climatic chamber. The results show that the use of CO2 cured binder not only helps to reduce the environmental footprint of the material but also contributes to the electrical conductivity parameters in the saturated state, which may be important for outdoor applications. The results further indicate that composites based on conventional CEM I and CEM II cements provide relatively good electrical conductivity, while furnace slag-rich CEM III cements show significantly reduced ionic conductivity and higher impedance, making them less suitable for electro-conductive applications. In contrast, the CO2-cured cement/ladle slag system demonstrated the highest leachate conductivity and the lowest impedance in the saturated state, confirming its potential as the most efficient and environmentally beneficial binder for outdoor electro-conductive composites. The study thus confirms that combining alternative binders with electrically conductive fillers can lead to more sustainable and functionally advanced building materials of the future.