Ecoefficient Cementitious Materials with High Levels of Portland Cement Replacement Using Blast Furnace Slag

The portland cement (PC) industry is responsible for approximately 7% of all carbon dioxide (CO2) emissions in the world. Blast furnace slag (BFS) has been increasingly used as a substitute for PC, due to the efficient disposal of steel industry waste and reductions in CO2 emissions. The present work investigated the environmental benefits of cementitious materials with large volumes of BFS (up to 90% PC replacement for the S90 mixture) and the influence on porosity and compressive strength. By X-ray computed microtomography and mercury intrusion porosimetry, pore size distribution was assessed. Porosity was also evaluated by water absorption. The environmental impacts were investigated by analyzing the embodied CO2 emissions (ECO2) and embodied energy (EE) by using life cycle assessment methodology. Reductions of around 40% in the compressive strength of S90 were found, while reductions in EE and ECO2 were above 80%. The S90 showed higher porosity at the age of 28 days, but then promoted a more active pore closing effect over time, being nevertheless feasible for use in terms of porosity. The use of S90 is expected to increase durability due to its thinner porous matrix, and contribute to reducing environmental impact and advancing cleaner production.