Foundry slag has different characteristics from blast furnace slag, such as its high SiO₂ content and low basicity (CaO/SiO₂ < 1), which prevent it from being used as a cementitious component. Lime slurry is a waste product with a high CaO content and can be used to increase the basicity of the mixture. The aim of this study is to obtain new supplementary, eco-cementitious material composed of foundry slag and lime sludge. The compositions were designed with binary basicity (molar ratio of CaO/SiO₂) ranging from 1.0 to 1.4. Clinker was replaced with the proposed material in the range of 6–34 wt% and the performance of the different cement compositions was tested. The results showed that replacing 20 wt% of clinker with the new eco-cementitious material with binary basicity of 1.2 resulted in cement with the same mechanical strength as the reference cement. The new material reacted with free CaO to generate additional calcium silicate hydrate. The initial setting time of the cement containing the new eco-cementitious material was 240 min, acting as hydration reaction retardant. The technical feature of the new eco-cementitious material allows the use of both wastes in cement composition, contributing to the requirements of circular economy.

One of the alternatives for reducing carbon emissions in the steel industry is the use of bio-coals. However, the use of biomass and its derivatives in steelmaking processes presents technical challenges due to their different chemical and physical characteristics to fossil fuels. In this context, this study aims to evaluate the effect of hydrochloric acid on the demineralization of eucalyptus charcoal, in order to understand its properties and potential application in the steel industry. To this end, the charcoal was subjected to a demineralization process using hydrochloric acid, varying the liquid-solid ratio (10:1 – 20:1) and molar concentration (1 - 3 M). The samples were then filtered, washed with deionized water and dried in an oven. The biochar was then characterized by determining surface area, moisture content, volatile content, ash content, fixed carbon content and kinetic analysis. The results showed that the surface area of the treated biocarbons increased by up to 438.38%, there was a reduction in the ash content of up to 91% and the activation energy of the gasification reaction varied between 54.8 and 109.9 kJ/mol.