Influence of the addition of waste graphite powder on the physical and microstructural performance of hydraulic lime pastes

The use of waste materials contributes to the improvement of the life cycle assessment of building materials, while traditional binders with a low carbon footprint enhance building sustainability. Isostatic graphite powder waste has not been used in the industry in spite of the huge quantities of it around the world. However, hydraulic lime is a traditional binder which requires low energy during manufacture. Hence, the aim of our research was to investigate the possibility of incorporating graphite waste powder into hydraulic lime pastes. Batches with different hydraulic lime NHL-5 replacements by graphite, ranging from 0% to 50%, with and without plasticizer were blended. Their mechanical characteristics and physical characteristics, namely, water absorption and thermal properties, together with the microstructure were analyzed. Among other effects, the addition of EDM graphite increased the compressive strength of the samples by almost three times while reducing the open porosity and the water absorption coefficient, enabling a wider use of these limes in building applications.