Microscopic Particles Offer Lean and Green Concrete

Researchers from Rice University developed micron-sized calcium silicate spheres that facilitate stronger and greener concrete

Rouzbeh Shahsavari, assistant professor of materials science and nanoengineering and graduate student Sung Hoon Hwang both from the Rice University formed spheres in a solution around nanoscale seeds of a common detergent-like surfactant. The spheres possess ability to self-assemble into solids that are stronger, harder, more elastic, and more durable as compared to ubiquitous Portland cement. In the previous research in 2017, the team developed self-healing materials with porous and microscopic calcium silicate spheres. The new material is not porous, as a solid calcium silicate shell surrounds the surfactant seed. The researchers found that manipulating surfactants, solutions, concentrations, and temperatures during manufacture can enable to control the size of the spheres that range from 100 to 500 nanometers in diameter.  Moreover, spheres allow advanced functionalities in synthetic materials.

In 2017, the team attempted to make platelet or fiber building blocks for composites. However, in the current research, the team used spheres to create strong, tough, and adaptable biomimetic materials. Two common surfactants were used to make spheres and compress their products into pellets for testing. The team found that DTAB-based pellets compacted best and were tougher than either CTAB pellets or common cement. Moreover, the surfactants showed high electrical resistance. The size and shape of particles possess a significant effect on the mechanical properties and durability of bulk materials such as concrete. Moreover, spheres with different diameters can be mixed to fill the gaps between the self-assembled structures, which leads to higher packing densities and offer mechanical and durability properties.

Increasing the strength of cement enables less use of concrete that decreases weight and the energy required in making concrete. Moreover, it helps in reducing carbon emissions associated with cement’s manufacture. The resulting material can be more resistant to damaging ions from water and other contaminants as spheres pack more efficiently than the ragged particles found in common cement. Moreover, the material requires less maintenance and less-frequent replacement. The research is published in the American Chemical Society journal Langmuir on September 25, 2018.