Construction and demolition waste as raw material for concrete and construction elements obtained through alkaline activation

Abstract

Portland cement (OPC) has been commonly used in concrete production. However, it has been questioned for its excessive consumption of natural resources and energy, and the high emissions generated in its production process. On the other hand, the construction sector also contributes to the environmental impact by generating construction and demolition waste (CDW) that is not used. This has motivated the development of alternative cements with a lower carbon footprint and the reuse of CDW to comply with the Sustainable Development Goals (SDG) and the principles of Circular Economy. Here we demonstrated the feasibility of producing alkali-activated hybrid concrete using a mixture of powders from CDW grinding. As alkaline activators, we used a solution of sodium hydroxide and silicate (NaOH+Na2SiO3) and sodium sulfate (Na2SO4). The OPC proportion was 10% and 30%, respectively. For an integral CDW use, we used 100% recycled aggregates. The designed concrete had the mechanical strength required by the NSR-10 Seismic Resistant Standard to be classified as structural. Additionally, its global warming potential (GWP) was 68% lower than that of an OPC-based concrete with the same specification. This concrete was used in the production of precast elements such as solid blocks, vertical perforation blocks, and paving stones that met the specifications required by the Colombian technical standards.