Secondary Raw Materials for a Circular Economy in Concretes

The construction sector is the most resource intensive industry in Europe, it uses around 50% of available raw materials and has significant environmental impacts and costs. Construction industry is, therefore, required to become more and more sustainable and the use of Secondary Raw Materials (SRM) represents a viable solution. Research on building materials is, nowadays, working on the valorisation of SRM from different waste streams to replace conventional cements, which production is responsible for energy consumption and CO2 emissions, or aggregates extracted from natural sites. Alkali-activated cements (AACs), among them those based on slags from steel plants (ground-granulated blast-furnace slag - GGBS or GGBFS), activated by alkaline liquids to produce alkali-activated binders (AABs) are considered sustainable alternatives to ordinary Portland cement (OPC). Concretes based on AABs have gained considerable attention due to their reduced environmental impacts and costs combined with high technical performance. This paper reports on promising experimental results achieved for an innovative concrete prepared with an AAB consisting in a combination of GGBS (60% wt), natural calcium carbonate filler (30% wt) and silica fume (10% wt). The concrete has been extensively tested to assess technical properties such as workability and mechanical performance (compressive strength, elastic modulus, stress-strain behaviour). This research encourages the use of AABs in concrete technology and, in general, of recycled materials in the construction sector.