There are some in the building industry — perhaps even a majority of people — that believe concrete is either waterproof, or that it is somehow immune to any negative effects from exposure to moisture. However, typical concrete is porous, with many tiny cracks, allowing water to penetrate. Exposed to freeze-thaw weather cycles, that water can cause the existing micro-cracks within the crystalline structure of the concrete to expand, and ultimately weaken the assembly’s integrity allowing for much larger cracks.
If only there was a concrete that could resist water, and minimize cracking.
Under the direction of civil engineering professor Konstantin Sobolev, researchers at the University of Wisconsin at Milwaukee think that might have something for the building industry that will do just that. Laura Otto at Phys.org has more:
Super-strong polyvinyl alcohol fibers or high-density polyethylene fibers, each the width of a human hair, are mixed into the concrete and bond with it. When cracks begin, the fibers prevent them from opening and becoming larger gaps.
In fact, Sobolev isn’t trying to eliminate cracking. He wants to direct the process in a preferred way, resulting in evenly distributed microcracking. This disperses the load so that tiny cracks remain small while the material’s superhydrophobic features form a water barrier.
This architecture, Sobolev says, allows the material to withstand four times the compression of traditional concrete and have 200 times the ductility, or flexibility under stress.
Since science is more fun with a video, here is the professor and postdoctoral researcher Marin Kozhukhova demonstrating some of their findings: