This is a pretty cool article
This is basically what it is about:
As if the scientific evidence isn't enough, Barsoum has pointed out a number of common sense reasons why the pyramids were not likely constructed entirely of chiseled limestone blocks.
"How energy intensive and/or complicated can a 4,500 year old technology really be? The answer to both questions is not very," Barsoum explains. "The basic raw materials used for this early form of concrete-limestone, lime, and diatomaceous earth-can be found virtually anywhere in the world," he adds. "Replicating this method of construction would be cost effective, long lasting, and much more environmentally friendly than the current building material of choice: Portland cement that alone pumps roughly 6 billion tons of CO2 annually into the atmosphere when it's manufactured."
http://www.livescience.com/history/0705 ... amids.html