Narrator: This is Science Today. On any given sidewalk, you're more than likely to encounter cracks in the pavement. These cracks develop when fluids in the cement mix with silica in the concrete, forming what's called an alkali- silica gel. Researcher Bill Carey of the Los Alamos National Laboratory says in time, this gel expands and causes cracks.
Carey: What we wanted to do was to study this to learn the mechanisms and to propose solutions to prevent this from happening either by changing certain chemical aspects of cement in such a way that gel would maybe not form or if it did form, not be a swelling gel and cause cracks.
Narrator: The first step towards prevention is detection, so Carey helped develop a quick, color-coded stain test, which is safer than the standard test that uses uranyl acetate.
Carey: Urunayl acetate is a heavy metal, mildly radioactive and presents real disposal problems, in addition it was sort of hard to work with because you put the urunayl acetate solution on and then you look at the surface under ultraviolet light.
Narrator: For Science Today, I'm Larissa Branin.