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BUILT LIKE A BRICK

THESE DAYS, E-tailing downplays the term “brick and mortar.” However, this building material duo has interesting aspects, as described in Arianne Shahvisi’s “Diary” piece “Life in a Tinderbox,” in London Review of Books, March 18, 2021. 

Arianne Shahvisi is Senior Lecturer in Ethics at England’s Brighton and Sussex Medical School. But her background is varied indeed: natural sciences, astrophysics, philosophy of physics, culminating in a Cambridge Ph.D. in philosophy. I get the impression that “culminating” in no sense implies “ending with.” Here are tidbits from her article touching on brick, mortar, cement, concrete, and living biomass versus human-made stuff. 

Mortar. Shahvisi opens by noting, “The cheapest way to make strong mortar is to add washing-up liquid. I learned this from my father, with whom I’d fix cracks and repoint brickwork when I was a child…. A shovelful of cement powder, some bright orange construction sand, water from a bucket, and, finally, a squirt of washing-up liquid.”

Image from bombaytiles.com.

I followed through in researching this trick. The squirt of kitchen detergent incorporates bubbles into the mortar that make it smoother, more pliable, and easier to work. On the other hand, er, trowel, there’s disagreement about its effect on mortar strength. One source, hunker.com, notes, “Liquid dish detergent should not be added to ready-mix concrete, as it already contains an air entrainment agent.”

Roman Concrete. Shahvisi observes, “Romans had their own secret ingredient for concrete: seawater. It reacts with pozzolana and lime to form aluminium tobermorite, whose crystalline structure runs through the mix like a microscopic scaffold, an atomic simulacrum of the steel skeletons used to reinforce concrete from the end of the 19th century.”

Above, Roman seawall at Portus Cosanus, almost 2000 years old. Image from Archinect. Below, the Pantheon in Rome, built 113–125 A.D. Image from history.com.

Shahvisi continues, “This particular chemistry, which was a puzzle until very recently, explains why the piers at Portus Cosanus still stand, and why the Pantheon remains the largest unreinforced concrete dome in the world.”

Built Like a Brick. Shahvisi comments on the geometry of the common brick: “Vitruvius, who wrote extensively on human proportion, would have been pleased to know that the dimensions of modern bricks are designed to suit the span of a human hand. Bricklayers must be able to hold a brick in one hand and a trowel in the other.”

Image from brocross.com.

Shahvisi cites that the hardest and densest bricks come from her birthplace, Accrington, in the north of England. “Nori bricks,” she explains, “get their name from an accidental inversion of ‘iron’, which was stamped backwards on the ‘frogs’ (the depression in the centre of the brick) of the first batches in 1887, announcing their high iron content.” 

 Cement and the Environment. Shahvisi writes, “Cement production involves intensive quarrying, dust pollution, high-heat kiln combustion and the release of carbon dioxide through calcination reactions.” 

“There is now more concrete in the world,” says Shahvisi, “than any other man-made material. After fossil fuels, it is the largest source of carbon dioxide, contributing 8 per cent of emissions, which puts it ahead of aviation and agriculture.”

A Global Tipping Point. Shahvisi cites, “A recent paper in Nature noted that in 2020 the weight of human-made stuff exceeded living biomass for the first time. (It was just 3 per cent of biomass in 1900.) While trees and other vegetation weigh in at around 900 gigatonnes, buildings, roads and other infrastructure add up to 1100 gt (animals contribute 4 gt, half the weight of plastic on land and sea).”

Image by Itai Raveh from Scientific American.

Philosopher Shahvisi makes a compelling point about human history. ds

© Dennis Simanaitis, SimanaitisSays.com, 2021  

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