The researchers found that the calcium-silicate-hydrate nanoparticles were arranged either in a manner similar to oranges randomly jam-packed in a box or like the pyramidal arrangement of oranges in a grocery store. With these two arrangements, the particles fill, respectively, 63 and 74 percent of the volume of the cement paste, the rest being water and air. The relative volumes that the nanoparticles occupy in the paste control the mechanical properties of the cement paste, the researchers found.
Ulm and Constantinides are now planning to change the components in cement–one idea is to substitute magnesium for calcium–so that it takes less heat to make cement but the resulting nanoparticles still have the same packing arrangement as the calcium-silicate-hydrate nanoparticles.
They also plan to study the nanoparticle until they understand it down to the atomic level. This will give them even more freedom to nanoengineer cement, Ulm says. “We could add chemicals to it in order to improve the performance [of concrete] with maybe less cement, or the same cement that gives higher strength.”
With two billion tons of cement being produced in the world every year and concrete demand rising with the growth going on in China and India, Ulm says that it is imperative to reduce concrete-related carbon-dioxide emissions as part of the effort to combat global warming.