RESEARCH
Smart cement: more durable roads and cities However it is built, it must be maintained and eventually renewed. Millions of tons of waste are released every year and new cement has to be produced, which causes extra CO2 emissions. In addition, the UN expects that by 2050 two-thirds of the world’s population will live in cities, which means that a huge amount of (concrete) buildings must have been built by then. To prevent a corresponding amount of CO2 -emissions as a result, these new cities and roads must be built with sustainable and smart concrete. Engineers tackling this issue with smart materials typically enhance the function of materials by increasing the amount of carbon, but doing so makes materials lose some mechanical performance. By introducing nanoparticles into ordinary cement, Northwestern University researchers have formed a smarter, more durable and highly functional cement. Cement is the most widely consumed material globally, with the cement industry accounting for 8% of human-caused greenhouse gas emissions. Aiming for
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cement composites with a reduced carbon footprint, the Northwestern Research team, lead by environmental engineering professor Ange-Therese Akono, investigated the potential of nanomaterials to improve mechanical characteristics. It is believed that nanomaterials reduce the carbon footprint of cement composites, but until now, little was known about its impact on fracture behaviour. An important question was to increase the fraction of carbon-based nanoma-
terials within cement matrices while controlling the microstructure and enhancing the mechanical performance. Specifically, the team looked at the fracture response of Portland cement reinforced with one- and two-dimensional carbon-based nanomaterials, such as carbon nanofibres, multiwalled carbon nanotubes, helical carbon nanotubes and graphene oxide nanoplatelets. Nanomaterials are shown to bridge nanoscale air voids, leading to pore refinement, and a decrease in the porosity and the water absorption. An
