Abstract Alkali-activated slag (AAS) is a low-carbon alternative to Portland cement with potential for functional civil engineering applications. Electrothermal energy conversion based on the Joule effect, achieved through electrically conductive admixtures (ECAs), enables new functions such as preheating or surface defrosting of civil engineering materials. This study examines the influence of carbon black, graphite powder, and metal waste from 3D printing on the electrothermal performance of AAS mortars. Mixtures containing 4–8.75 Wt.% graphite powder, 1–2.5 Wt.% carbon black, and 5–250 Wt.% metal waste (by mass of solid particles) were evaluated in terms of the electrical behavior, temperature evolution, power demand, and electrothermal conversion efficiency. Metal waste did not provide meaningful electrothermal conversion potential for AAS mortars. In contrast, carbon black and graphite powder significantly enhanced the electrothermal response, with the highest efficiencies observed near the percolation threshold. Despite exhibiting lower temperature rises than more highly doped systems, mixtures containing 6.25 Wt.% graphite powder and 1.5 Wt.% carbon black achieved peak efficiencies of 79.5 and 54.6%, respectively. Increasing ECA content increased power consumption and temperature rise but reduced electrothermal efficiency, likely due to localized heating and enhanced surface- and electrode-related energy losses. These findings identify the percolation threshold as a key design parameter for efficient electrothermally active AAS mortars.
Fiala et al. (Mon,) studied this question.
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