Iris Publishers - Scholarly Open Access Journal of Civil and Structural Engineering Green Construction Materials and the Circular Economy Abstract This opinion article concerns the minimization of the environmental impacts of the cement and concrete industries. The article identifies the processing of carbon dioxide that results from cement production and the incorporation of construction and demolition waste on concrete as key objectives for environmental sustainability, discusses concepts related to both objectives, and presents the mission of c5Lab - Sustainable Construction Materials Association, a consortium that intends to contribute to the greening of the cement and concrete industries. Keywords: Sustainability; cement; concrete; carbon dioxide; construction and demolition waste; circular economy Introduction Reinforced Concrete stands as the main Structural material for large buildings and many other Civil Engineering works, with many emblematic structures, from the...