How does concrete harden?

Concrete is all around us. It makes up the buildings we live in, the sidewalks we walk on, the ramps we do our sick skateboard tricks on … but how is it made? How does it go from a thick, sludgy paste into a hard, smooth surface? We asked engineering professor Matthew Adams to help us find the answer.Got a question that seems to keep getting harder? Send it to us at BrainsOn.org/contact, and we’ll use all our ce-MENTAL ability to find the answer!