A photo of the dry ash (bottom-center) I dumped in a shallow sand pit on the shores of Detroit Lakes, Minnesota. It got me thinking about the potential origins of concrete.
A couple days ago I prepped a fire pit on the sandy shores of Detroit Lakes, Minnesota. As I shoveled dry ash made from previous fires out of the pit and into a shallow hole in the sand, I imagined myself in pre-Vitruvius days on a Mediterranean coast doing the same thing, or something similar. “Perhaps this is one of the origins of the recipe for concrete?” I thought. I envisioned someone thousands of years ago dumping ash into the sand in a similar way (with lime as well). Maybe it was volcanic ash, or that from a former campfire.
The Romans used this concrete stuff for infinite reasons — from building underwater docks to linear roads to fortifications and infrastructure in general. The architect Vitruvius was the first to scribble down the recipe for concrete. But certainly this knowledge circulated amongst laborers and masons before hand.
One of the concrete secrets is in the texture and quality of the sand. Here is what Vitruvius said in Book 2, Chapter 4: Sand for Concrete Masonry:
In concrete structures one must first inquire into the sand, so that it will be suitable for mixing the mortar and not have any earth mixed in with it. These are the types of excavated sand: black, white, light red, and dark red. Of these the type that crackles when a few grains are rubbed together in the hand will be the best, for earthy sand will not be rough enough. Likewise, if it is thrown onto a white cloth and then shaken off, if it neither dirties the cloth nor leaves behind a residue of earth, it will be suitable.
Thus, keep the soil out of your sand when mixing concrete, this whether you are mixing for a foundation of a tool shed or trying to impose your imperial will on others around you.
Molly is finalizing the mosaic grouting process on a reused terra-cotta potter salvaged from someone’s trash pile.
It is the weekend and projects are happening: plans have been set in motion to slow-smoke some baby back ribs, and Molly is out front of her sister’s Valley City home, toiling away at a mosaic project. I’ve busied myself with reading James Belich, The Victorian Interpretation of Racial Conflict: The Maori, The British, and the New Zealand Wars (McGill-Queen’s University Press, 1986 & 1989), but have set it down to do a bit of immediate chores.
So while taking the trash out from the kitchen to the dumpster, I passed by Molly’s ongoing mosaic project. Then I started thinking about how Molly’s mosaic project today reminded me of the Late Roman mosaics I saw a year ago in the historic archaeological village of Kourion, Cyprus. Then I started thinking about how historians and archaeologists — depending on what cultural settings they were born into, and depending on what previous experiences they have had — bring individual and disparate meanings to the stuff they come across. (This may be getting a bit too self-absorbed, so if you’ve noticed it, and it offends you, please stop reading here if you already haven’t. I will not take offense. But it is a line of thinking with universal application.)
So without slamming out any more dialog (we are packing up and readying to go, which is timely to end this short entry), I will upload a couple pictures I snapped a year ago in Kourion, and a couple pictures from today in Valley City. Taking massive leaps through space and time, this is what I call a global and local longue durée of mosaic history, from Kourion, the Roman Empire, to Valley City, North Dakota.
Close-up mosaic detail from Kourion, Cyprus.
A mosaic from a Roman gladiator’s home in Kourion, Cyprus. Mosaics are not for cowards.