The cement industry is a major contributor to pollution within the construction sector primarily due to the production of clinker, the main component of Portland cement (PC), which is highly carbon- and energy-intensive. Furthermore, the construction sector consumes a vast amount of natural resources to produce building materials. Therefore, the search for more sustainable construction materials is crucial for the transition into a more eco-efficient model.
A short-term alternative to completely replacing PC with supplementary cementitious materials (SCMs) involves partially replacing clinker and producing blended cement (BC). This well-established strategy reduces the carbon footprint of the cement by lowering the clinker content. Partial clinker replacement is cost-effective, provides reliable properties and durability, uses readily available materials, and is easy to employ for building and civil engineering purposes. The global adoption of this strategy can significantly reduce the carbon emissions of the cement industry, and virtually all countries can locally generate suitable additions to substantially decrease the clinker-to-cement factor. In addition, combining two SCMs in ternary BC has recently proven effective in maintaining desirable properties, even with higher clinker substitutions, leading to higher CO2 reductions.
Medium and long-term alternatives are increasingly being considered. These include suitable, less carbon-intensive alternative cementitious materials (ACMs) that can replace Portland cement (PC).
Some of the most promising ACMs include alkali-activated cement (AAC) and magnesium-based cement. Using waste and by-products in the formulation of ACMs is an environmentally friendly andsustainable practice that reduces the carbon footprint and promotes a circular economy.

Acti2Cem project is based on the hypothesis that alternative binders to PC can contribute significantly to the decarbonization. The novelty of Acti2Cem lies in its approach to develop cementitious materials using low-grade and secondary clay-based and Mg-based sources as precursors for BC, LC3
, AAC, RMC, and MSH cements. This is the first project to explore such materials at this scale. The proposed clay-based precursors include low-grade clays unsuitable for thermal activation, water treatment sludge, excavated soils, and by-products from clay purification and milling. Additionally, the Mg-based precursors consist of cyclone dust from magnesite calcination and tundish deskulling waste from steelmaking. This innovative approach aims to reduce reliance on primary resources, enhance sustainability, and contribute to the decarbonization of the construction industry.

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