on concrete

Stephanie White

technology and brute use

Almost three tons of concrete are produced every year for each man, woman and child on the planet. It is now second only to water in terms of human consumption. Yet how has the astonishing take-up of this new medium within little over a century been accommodated into our mental universe? While it has transformed the lives of many people, in Western countries it has been widely vilified, blamed for making everywhere look the same, and for erasing nature. Architects and engineers, although they have primary responsibility for ‘interpreting’ concrete, are not the only people to employ the medium, and many other occupations - politicians, artists, writers, filmmakers, churchmen - have made use of concrete for purposes of their own. The results are often contentious, and draw attention to the contradictions present in how we think about our physical surroundings.’ 1

1 ‘The Metaphysics of Concrete’ uploaded to YouTube by UCLLHL on 27 February 2012. Professor Adrian Forty, UCL Bartlett School of Architecture.

—Adrian FortyIn this quest to define a material culture of architecture we must address concrete as both a building material and as a cultural artefact. Epithets such as Bob Marley’s 1973 concrete jungle ‘Where the living is harder’ or ‘the concrete jungle’, a 1982 film about a women’s prison, reinforce concrete’s obduracy. The Berlin Wall was made of concrete, as is the Israel/West Bank separation barrier in places known to be advantageous to snipers. These are not fences, or steel barriers, they are opaque, graffiti-covered, high walls of reinforced concrete, mechanically installed and militarily guarded. It is the ungiving nature of concrete that was declared essential for a protective USA southern border and that rallies the imagination of its proponents. Concrete is immutable, like the Coliseum, and it is this immutability that both protects and raises the ire of those caught in such immutable facts.

Raw concrete was and still is identified as the material of war, from the massive concrete blocks of the Atlantic Wall in WWII, to the pillboxes that still occupy every headland looking over the entrance to Halifax Harbour. Nothing is as sheltering, safe and bullet-proof as concrete. It repels attack. The concrete seen by Andrey Chernykh at the Semipalatinsk Nuclear Test Site, functional and unadorned but now in ruins, is so easily interpreted as a kind of nuclear holocaust Land Art – photographs allow this denatured response to great plinths toppled in the wake of a nuclear explosion. But being there, as Chernykh was, is not art, it is a warning of the scale of concrete’s vulnerability.

In the past decade of news coverage of both the destruction wrought in Syria and the waves of bombings in Gaza City, one is struck by the sheer amount of concrete and rebar left in great tumbled piles of collapsed buildings. No trees, no wood, no parks or lawns, Palestinian refugee camps and Gaza itself are dense concrete worlds. Why is concrete the building material of choice? There are geological reasons: North Africa and the Middle East sit on a shield of limestone, interleaved with layers of sandstone. 2 Calcareous, limestone derives from fossils and shells, sand comes from the edges of the ocean, oil from the animals and vegetation that lived there: it is geology itself that produces the wealth, the tensions and the landscapes of the Middle East, and has done so for a long time: the pyramids are sandstone blocks, faced with limestone sheets. Photographs of Palestine in the 1920s show a sandstone architecture. However, quarrying and building in stone is not the process for quick reconstruction in war, concrete clearly is.

2 Stewart Edgell , ‘Significance of reef limestones as oil and gas reservoirs in the Middle East and North Africa’, 10th Edgeworth David Symposium, University of Sydney, September 4-5, 1997.

Concrete debris can be re-used as aggregate: it isn’t as strong, but there is lots of it. All the steel reinforcing bars and mesh can be hammered out and re-used, and concrete can always be mixed in small batches, by hand if necessary. Not that the entire Gaza Strip is in rubble; one can find concrete companies with perky websites there just as anywhere else. The Israeli blockade allows the entry of construction materials from Egypt only for the Palestinian Authority which does not operate in Gaza. Nonetheless, the territory sits on limestone, abuts an ocean full of sand, and is provided with rubble of all kinds on a regular basis.

How does one get from limestone to concrete? Limestone fired at 1450C frees CO2 from calcium carbonate to form calcium oxide, or quicklime. Gypsum is added, and depending on geography, a number of other additives such as fly ash, blast furnace slag, silica fume, various clinkers, sometimes metakaolin (to make it very white). Strangely, cements are considered natural materials, I suppose because they are made of ‘natural’ mined minerals, such as limestone and bauxite. Calcium sulfoaluminate low-energy cements require lower kiln temperatures, less limestone, thus less fuel consumption and CO2 emissions, but ‘significantly higher’ SO2 emissions which, if I recall, leads to acid rain. Green cements using waste containing calcium, silica or iron, can replace clay, shale and limestone in the kiln, and other waste material can be used as fuel rather than coal or natural gas. Majd Mashharawi, a young civil engineer in Gaza made headlines in 2018 for her concrete block, Green Cake, made from building rubble and ash from domestic fires to power generators. The blocks use less cement than standard concrete and have passed strength tests for construction.

At the opposite end of the concrete research spectrum are engineered cementitious composites, ECC 3 , a ductile concrete that does not use coarse aggregate but rather a coated network of fine polymer fibres within the cement that slide under stress, so no irreparable breaches, just thousands of fine cracks, dusted with cement, that self-repair with water. ECC’s flexibility – its internal slipperiness – does not allow it to shrink and crack. Forty times lighter than conventional concrete, clearly it is valuable in earthquake zones. In 2003 it was sprayed in a 20mm layer over 600m 2 of the cracking, leaking, spalling 1995 Mitaka Dam in Japan.

3 Victor Li, University of Michigan, early 1990s. Li states: ‘Engineered Cementitious Composites (ECC) is a material micromechanically designed with high ductility and toughness indicated by multiple microcracking behavior under uniaxial tension.’

Novacem, a UK research facility, has developed a magnesium silicate-based strong cement which absorbs CO2 as it hardens, making it carbon negative. Geologically speaking, limestone is very common throughout the world, as are magnesium silicates. Although one can develop a new carbon negative cement, getting it to replace existing, long-standing industrial processes is more difficult.

I include this research as it is interesting – concrete is not static but evolving, but this only marginally affects the material culture of concrete, which is less about capacity as it is about associations as the use of concrete bounces between the crude and the sophisticated.

concrete’s ubiquity in war

WWII USSR-made concrete bombs used concrete casings for bombs up to five tons, filled with either explosives or chemicals. Inexpensive but fragile Soviet slate mines assembled cast asbestos concrete slabs (or slates) into boxes filled with explosives – only the fuses were metal and so the bombs escaped mine-detectors.

Solid low-collateral damage small-dimension concrete bombs were used by the US Army in the late 1990s and again in the Iraq War. In theory, they produce less collateral damage in civilian areas because there isn’t a wide spread of shrapnel. Some concrete bombs are loaded with explosives; many are concrete alone, relying on speed and weight to knock out a narrow target – a 300kg concrete bomb was dropped by a French Mirage on a Libyan tank in 2010: effectively a GPS laser-guided boulder.

Iran’s ultra-high performance concrete, UHPC, is made of sand, cement, powdered quartz and, variously, polypropylene fibres, long steel fibres and various metal-oxide nanoparticles. The stronger the concrete bunkers (and UHPC is seven times stronger), the larger and more penetrating must the missiles be. The larger the missiles and bombs, the larger and more reinforced the bombers must be. The Guided Bomb Unit-57A/B Massive Ordnance Penetrator of the US Air Force weighs 15 tons and can penetrate 200’ of hardened concrete. 4

4 ‘Smart concrete’, The Economist, 3 March 2012

On one hand we have great chunks of concrete dropping from the sky onto tanks, on the other we have nanotechnology escalating bombing and bunkering to a scale unimaginable to civilians.

concrete’s longue durée

First farmers for 2500 years to settle Gilboa in Israel. David’s Curse Lifted, Mizpeh Gilboa, Israel. Two of the new settlers at Mizpeh Gilboa are pictured mixing cement and sand for their new houses. So far six permanent buildings have been erected in the settlement plan according to the settler’s choice. Water is still brought up by tankers from Nurit, but a pipeline [from] Beisan Wells is planned

TopFoto IPU447438. www.topfoto.co.uk

The 1962 UPI photograph above, and its headline indicates the myth of terra nullius prevalent at the time of the 1967 War: that no one lived in this new land, and if they did, they weren’t taking advantage of it. It also shows how concrete allows relatively unskilled fabrication: a couple, sand, rock, cement and tankered-in water. And yet the results are so permanent that they take on the inevitability of geology. It is the re-mineralisation that cement goes through that so distorts the legitimacy of construction.

Thomas Rau proposes that nature is a bank and if we treated it as such we wouldn’t exploit it as we do. 5 Every building should be considered as a bank of materials, valuable because finite, like currency, which circulates over and over again through time and society, an idea that presupposes a certain salvageability as whole material units rather than the pulverising demolitions that usually happen when a building reaches the end of its usefulness (not necessarily its life, but the limits of appreciation of its value). It is assumed that buildings have a life span.

5 Thomas Rau and Sabine Oberhuber. Material Matters, 2018. Dutch version only. thomasrau.eu

Le Corbusier’s work at Chandigarh is a hugely complex architecture built with a single material, concrete, which once cast cannot revert back to its original ingredients – the chemical reaction when water meets quicklime cannot be undone. Correctly built, this kind of architecture is forecast to have an infinitely long lifespan; deconstruction and reuse of the materials is not considered. Unlike concrete buildings regularly demolished in the western world, Le Corbusier’s Chandigarh project persists: there has been little development pressure to constantly rebuild in what was once the de-colonising, developing, third world. The utopian socialist roots of modern architecture that meant something in the developing world, passed out of fashion in the developed world where it is now seen as a style (or a necessary utility), not as something for social good. Indeed, by the 1970s, projects just twenty years old, such as Yamasaki’s Pruitt-Igoe in St. Louis, were totally discredited as the social ambitions of the architecture did not match at all the political and social fears of race and poverty.

Le Corbusier, Secretariat, Complexe du Capitole, Chandigarh, India, 1952

Shaun Fynn. www.studiofynn.com

Architecture as a material bank references a pre-industrial model where buildings were assembled and dis-assembled by hand. Rau extends it to industrial processes, with the circularity potential of each material as the precondition for its use. This has the potential to redevelop modernism without the extravagance of material exploitation that came so easily to the West, where the environment was assumed to be infinitely patient, self-healing the wounds we inflicted by fire, by mining, by impermeable cities, by voracious appetites. An architecture of circularity assumes an impermanence to buildings whereby they can be constantly in flux, parts replaced, parts repurposed. This points out how much our future will necessarily be the polar opposite to the both the still, eternal, unmoveable architecture of Chandigarh, and the wrecking ball.

an architecture of intentional material archaeology

Two projects that understand the complexity and contradictions in the use of concrete are Wang Shu’s Ningbo History Museum of 2008, and Frida Escobedo’s Serpentine Pavilion of 2018. When much of China seems to be the playground of capitalist architectural excess: an excess of ambition and money, the new China seemingly free of inhibiting content, we have Wang Shu building from the rubble of villages destroyed to make way for new projects. Ningbo History Museum is built from tile, brick, concrete and stone salvaged from other buildings, sites of collapse, rubble: each piece comes with a fragment of history and unrepeatable form, giving an elasticity to its use: fit is unpredictable but follows very old techniques. New concrete, and it is extensive, is poured into bamboo formwork. There is a patience both to assembly and to the concept as a whole: the building evolves from its materials. Wang Shu is reclaiming China’s deep past — not historicism, but a sophisticated historical thinking.

Wang Shu, Ningbo History Museum, Ningbo, China, 2008

Fernando Guerro, photographer. ultimasreportagens.com

Frida Escobedo, Serpentine Pavilion 2018.

© Frida Escobedo, Taller de Arquitectura, www.fridaescobedo.net © 2018 Iwan Baan

Frida Escobedo’s architecture in Mexico uses common, often salvaged, found materials; for the 2018 Serpentine Pavilion in London, she didn’t import her palette from Mexico, but looked for its equivalent: mundane inexpensive materials easily accessed. She found UK-manufactured concrete roof tiles and stacked them into semitransparent walls that shade and shadow, define and obscure: a complex architecture made of a materially insignificant building product. Wang Shu was building a museum, a strongbox of treasures; Frida Escobedo was building a pavilion to be taken down after four months. Both treated an insignificant (because so everyday) material culture of a local architecture and rendered it fugitive, otherworldly and exceptional.

Stephanie White has been the editor of On Site review since its beginning in 1999, and its publisher since 2000. On Site review is conceived of as a place to think about things, slowly.