Egyptians used concrete?

A professor from Drexel University claims that the Egyptians used a concrete-like material made from limestone to make some of the blocks forming Great Pyramids of Giza.

Barsoum argues that although the majority of the stones were carved and hoisted into place, crucial parts were not. The ancient builders cast the blocks of the outer and inner casings and, likely, the upper parts of the pyramids using the concrete.

Source: Drexel University

Related news article: Kansas City Star via New York Times

Some might say the discovery, if true, diminishes the engineering accomplishments of the Egyptians. I don’t think so. There’s something to be said for the invention of new processes and / or materials to creatively solve problems. It would also help explain how the engineers that completed the Pyramids of Giza were able to finally make the “perfect” pyramid shape while their predecessors failed with earlier pyramids.

The Drexel news release also claims that the Egyptian version of concrete might yield new modern processes that would make the production of modern concrete more cost effective and friendly to the environment.