Alkali-Activated Cements from Urban, Mining and Agro-Industrial Waste: State-of-the-art and Opportunities

Facing the beginning of the third decade of the twenty-first century, humanity faces an environmental threat that can pose some serious concerns regarding the life on the planet as we know it. The industrial sector is probably the most significant contributor to this concerning scenario, with the construction industry (CI) playing a leading role. Massive efforts have thus been directed to the research of more sustainable and environmentally friendly paths in the CI, showing a clear and sustained demand for new, bold and sustainable structural and non-structural materials. The development of alternative solutions to Portland cement (OPC) and relative products (e.g. mortars and concretes) is rapidly becoming the spearhead of said efforts, mostly due to the high contribution, in terms of CO2-eq, associated with cement production. The present paper focus on the recent developments associated with the incorporation of urban, mining and agro-industrial waste in construction materials, namely in alkali-activated cements. Scientific knowledge and its transfer into live-scale applications, based mostly on technical aspects, have been considered. At this stage, the transition from experimental studies to live-scale applications is probably the most relevant factor, as the secular knowledge associated with current solutions, combined with the heavy financial investments already made, is rapidly generating the sole biggest resistance to this necessary change of hearts and minds.