[ExI] chariots of the concrete mixers

[Damien Broderick]

[and it's not even April 1--even if the adventurous scientist *is* 
named Barsoom...]

great talk (despite dreadful audio glitches):
< 
http://media.irt.drexel.edu/mediasite/viewer/Viewer.aspx?layoutPrefix=LayoutTopLeft&layoutOffset=Skins/Clean&width=800&height=631&peid=cd83d501-eccb-497e-ad63-3d08a26de747&pid=7d3c4a1d-27fc-4692-b172-1196a53da689&pvid=535&mode=Default&shouldResize=false&playerType=WM64Lite  
 >

summary:

<http://www.livescience.com/history/070518_bts_barsoum_pyramids.html>The 
Surprising Truth Behind the Construction of the Great Pyramids
SHEILA BERNINGER and DORILONA ROSE - LiveScience


This Behind the Scenes article was provided to LiveScience in 
partnership with the National Science Foundation.

"This is not my day job." So begins Michel Barsoum as he recounts his 
foray into the mysteries of the Great Pyramids of Egypt. As a well 
respected researcher in the field of ceramics, Barsoum never expected 
his career to take him down a path of history, archaeology, and 
"political" science, with materials research mixed in.

As a distinguished professor in the Department of Materials Science 
and Engineering at Drexel University, his daily routine consists 
mainly of teaching students about ceramics, or performing research on 
a new class of materials, the so-called MAX Phases, that he and his 
colleagues discovered in the 1990s. These modern ceramics are 
machinable, thermal-shock resistant, and are better conductors of 
heat and electricity than many metals-making them potential 
candidates for use in nuclear power plants, the automotive industry, 
jet engines, and a range of other high-demand systems.

Then Barsoum received an unexpected phone call from Michael Carrell, 
a friend of a retired colleague of Barsoum, who called to chat with 
the Egyptian-born Barsoum about how much he knew of the mysteries 
surrounding the building of the Great Pyramids of Giza, the only 
remaining of the seven wonders of the ancient world.

The widely accepted theory-that the pyramids were crafted of 
carved-out giant limestone blocks that workers carried up ramps-had 
not only not been embraced by everyone, but as important had quite a 
number of holes.

Burst out laughing

According to the caller, the mysteries had actually been solved by 
Joseph Davidovits, Director of the Geopolymer Institute in St. 
Quentin, France, more than two decades ago. Davidovits claimed that 
the stones of the pyramids were actually made of a very early form of 
concrete created using a mixture of limestone, clay, lime, and water.

"It was at this point in the conversation that I burst out laughing," 
says Barsoum. If the pyramids were indeed cast, he says, someone 
should have proven it beyond a doubt by now, in this day and age, 
with just a few hours of electron microscopy.

It turned out that nobody had completely proven the theory...yet.

"What started as a two-hour project turned into a five-year odyssey 
that I undertook with one of my graduate students, Adrish Ganguly, 
and a colleague in France, Gilles Hug," Barsoum says.

A year and a half later, after extensive scanning electron microscope 
(SEM) observations and other testing, Barsoum and his research group 
finally began to draw some conclusions about the pyramids. They found 
that the tiniest structures within the inner and outer casing stones 
were indeed consistent with a reconstituted limestone. The cement 
binding the limestone aggregate was either silicon dioxide (the 
building block of quartz) or a calcium and magnesium-rich silicate mineral.

The stones also had a high water content-unusual for the normally 
dry, natural limestone found on the Giza plateau-and the cementing 
phases, in both the inner and outer casing stones, were amorphous, in 
other words, their atoms were not arranged in a regular and periodic 
array. Sedimentary rocks such as limestone are seldom, if ever, amorphous.

The sample chemistries the researchers found do not exist anywhere in 
nature. "Therefore," says Barsoum, "it's very improbable that the 
outer and inner casing stones that we examined were chiseled from a 
natural limestone block."

More startlingly, Barsoum and another of his graduate students, Aaron 
Sakulich, recently discovered the presence of silicon dioxide 
nanoscale spheres (with diameters only billionths of a meter across) 
in one of the samples. This discovery further confirms that these 
blocks are not natural limestone.

Generations misled

At the end of their most recent paper reporting these findings, the 
researchers reflect that it is "ironic, sublime and truly humbling" 
that this 4,500-year-old limestone is so true to the original that it 
has misled generations of Egyptologists and geologists and, "because 
the ancient Egyptians were the original-albeit unknowing-nanotechnologists."

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.

Egyptologists are consistently confronted by unanswered questions: 
How is it possible that some of the blocks are so perfectly matched 
that not even a human hair can be inserted between them? Why, despite 
the existence of millions of tons of stone, carved presumably with 
copper chisels, has not one copper chisel ever been found on the Giza Plateau?

Although Barsoum's research has not answered all of these questions, 
his work provides insight into some of the key questions. For 
example, it is now more likely than not that the tops of the pyramids 
are cast, as it would have been increasingly difficult to drag the 
stones to the summit.

Also, casting would explain why some of the stones fit so closely 
together. Still, as with all great mysteries, not every aspect of the 
pyramids can be explained. How the Egyptians hoisted 70-ton granite 
slabs halfway up the great pyramid remains as mysterious as ever.

Why do the results of Barsoum's research matter most today? Two 
words: earth cements.

"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."

"Ironically," says Barsoum, "this study of 4,500 year old rocks is 
not about the past, but about the future."