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By most measures, the world of concrete might at first seem a little boring. At a recent TED Talk however, University of Southern California professor Behrokh Khoshnevis unveiled his futuristic vision for 3D printing homes and buildings with a souped-up version of the stuff. If concrete can be successfully printed using his “contour crafting” method, the rectilinear grids found in most construction could be softened into strong, aesthetic curves. The formulation used would be a fiber composite with a compressive strength of 10,000 psi. By comparison, a typical batch of concrete used for homes, or the upper floors of tall buildings, has a strength of only around 3000 psi. It would also set fast enough to be fashioned on-the-fly into complex shapes, including arches and...