A natural history of concrete
By Gene Miller, January 2012
It all starts with ooids. Next thing you know, there’s a parkade.
What’s underfoot? The question holds professional interest for geologists and mineral explorers and, I suppose, for folks who think hell is down instead of Calgary in winter; though Jon Stewart recently quipped on the Daily Show, “hell is watching eight straight hours of Fox News.”
Think about it: we do a lot of digging and a lot of extracting—everywhere we can find riches to pluck. Adam, you’ll remember, was himself made from dust—earth itself; and Lilith, Eve’s precursor, from filth and sediment, as told in that collection of extra-biblical myths, the Midrashim. And as the Book of Common Prayer has it: “Dust thou art, and unto dust thou shalt return.”
We’re deeply connected to the material beneath our feet. Literally, it’s in our bones.
These matters have taken on currency and urgency because the planet is roiling: weather systems, ocean systems, land-based ecosystems, freshwater systems, soil systems. We don’t have rain, floods, tremors, high tides and big waves; increasingly, we have metaphors. There is the scientific thought that by releasing all that mineral energy underground with our extracting, drilling, blasting and fracking we are undoing Earth’s efforts, over millions of years, to balance the carbon budget.
We have freed the genie from the bottle. We have woken something underground. Things are getting biblical.
Locally, we believe we have more a tradition of gardening, husbandry and agriculture than a history of scraping, digging or delving. Still, sometimes, walking through sombre coastal woodlands in Gowlland Tod Park and other places, you can find incongruous weathered ruins of concrete foundations and low walls, and the occasional rusted remains of industrial machinery or piping. The crumbling vestige of ancient Mayan royal tombs? Gun emplacements? Martians?
At the bottom of Butchart Gardens, beyond the sunken garden which itself is a reclaimed limestone quarry, for example, still stands the tall brick chimney that expelled the heat and smoke from a cement works. Below, in the quiet coves of Tod Inlet, are remnants of the infrastructure that enabled vast quantities of this milled cement to be barged elsewhere—rotting wood pilings, paved staging areas now forested over, massive steel U’s sunk in concrete to secure marine ropes. And across Finlayson Arm sits the industrial remains of Bamberton—initially a friendly competitor of the Butchart operation, later merged with it to form BC Cement, itself later merged to form Ocean Cement, in turn a division of the Leheigh Heidelberg Group, third largest global cement producer. Must be something binding about cement....
Cement—I oversimplify as only the amateur can—is heated, pulverized (milled) limestone mixed with some other minerals. Wikipedia tells us that limestone is “a sedimentary rock composed of grains; however, most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and extraclasts. These organisms secrete shells made of aragonite or calcite, and leave these shells behind after the organisms die.”
I think it was John Wayne who said: “The only good ooid is a dead ooid.”
Pour water on cement and something magical happens: the grains reach out to hold hands...tightly. Add sand and aggregate—small stones of various sizes—and the result is concrete. Our civilization now is made of the stuff: most of our buildings, almost all of our roads, transportation and big energy infrastructure, and a couple of breakfast cereals I’ve tried.
While it’s impossible to know the number of exploratory digs in promising locations in and around the region, there is no missing the legacy of successful operations: enormous limestone pits now flooded; raw hillside gashes exposing a vertical hundred feet of the planet’s sandy history; and the still-lunar expanse of the so-called Construction Aggregates Producer’s Pit in Colwood, bisected by Metchosin Road. Though now recently decommissioned, it has been “in production” since 1919 (most of the cement-related activity in these parts dates from about that time) and in its day met local needs and also sent countless barge-loads of sand and gravel to the Mainland and Washington State. After 80 years, it’s fair to guess that there’s more Victoria in Seattle than meets the eye. Who knows? Maybe the Pike Place Market is ours, all ours!
If I have my science right, the friction and scraping from the formation and movement of continental glaciers ground up, then picked up and pushed, vast amounts of rocky material which was then deposited selectively, based on land contour, during the melting glacial retreat. As well, material travelling down long-ago rivers collected in various places, while the rivers themselves moved on or chose other courses. Visit the mile-square Colwood sand deposit, or the cliffs of sand that form the current Sayward Hill and Trio Gravel Mart near Mattick’s Farm in Cordova Bay, or the enormous landlocked Butler Brothers sand and gravel pit near the intersection of Keating Cross Road and Oldfield. The meandering paths of extinct rivers? Some long-ago delta? A million years of glacial dripping?
Or, as a more authoritative, if less euphonious, online source puts it:
Most of the surficial sediments in BC owe their origin to processes active during the last few million years (Quaternary).
During the Late Wisconsinan (25,000-10,000 years ago), much of the province was covered by a network of coalescing ice caps, valley, trunk, piedmont and cirque glaciers collectively termed the Cordilleran Ice Sheet. At this time, changes in base level resulting from isostasy and eustasy promoted sediment erosion and deposition. Subsequent climatic warming witnessed the decay of the ice sheet through active retreat and in situ melting. Sediment trapped in the ice consequently underwent active deposition beneath and adjacent to the melting glaciers; hence, deposits associated with deglaciation tend to reflect rapid and episodic events.
Want a second opinion? Here’s a rhapsody from the BC Ministry of Energy and Mines Quaternary Geological Map of Greater Victoria:
Quaternary deposits in Greater Victoria overlie an irregular glacially-scoured bedrock surface. The depth to bedrock can vary from zero to as much as 30 metres within the space of a city block.
Pre-Vashon sediments occur principally in the central and eastern parts of Saanich Peninsula, where they are up to 60 metres thick and have commonly been sculpted into a series of north-trending drumlinoid ridges and crag-and-tail features.
The Vashon till is overlain by the Capilano sediments, which were deposited at the close of the Fraser Glaciation when sea level was higher than present. The principal units of the Capilano sediments in the Victoria area are the Victoria clay and the Colwood sand and gravel.
The Colwood sand and gravel is a glaciofluvial outwash and deltaic deposit that occurs at the surface over much of Colwood and Langford. The maximum known thickness of the Colwood sand and gravel is 30 metres.
I’ve copied so much of this material because I’ve been dying to use “drumlinoid” in a column and also because I intend to casually drop “glaciofluvial” into my cocktail banter and use “crag and tail” as a pick-up line. (Oh, get the disapproving expression off your face. You know you’re going to name your next two kittens Isostasy and Eustasy.)
But I digress.
The most common use for cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, and water. When water is mixed with Portland cement, the product sets in a few hours and hardens over a period of weeks. Science can tell us how cement cements. It has nothing to say about why it chooses to, why it dedicates itself to this purpose.
Portland cement—so named because its colour resembled Portland Stone—was first produced about 160 years ago in England and Germany. The first cement production in Victoria came in the early 1900s courtesy of Robert Butchart at Tod Inlet and subsequently, in 1912, from the Portland Cement Construction Company of London, managed locally by Mr. H.K.G. Bamber. Both were drawn to Victoria because of the rich deposits of limestone. In the early part of the century, Victoria was the Portland cement supplier for much of the Pacific Northwest.
Water, sand, and ground-up exoskeletons. We owe a significant part of our local wealth and industrial legacy to the turbulent extremes of natural systems, and the suicidal, unplanned self-sacrifice of a zillion ooids. Ain’t nature grand?
I’m not suggesting you stay off the sidewalks out of respect for the departed, or trying to introduce morbidity into your future Sunday drives; but if you had any lingering doubts about the absolute connectedness of everything, or lack the grounds for a fundamentally pantheistic view of existence, consider, the next time you see the raw earth exposed: you pass, your flesh melts, your calcified bones remain. Eventually, you may live again, as a parkade.
This much I promise: and unto dust you shall return, you ooid, you.
Gene Miller is the founder of Open Space Arts Centre, Monday Magazine, and the Gaining Ground Sustainable Urban Development Summit.