A cautionary view on recycling waste products into construction materials

#recycling #miningwaste #construction #housing #africa #architects


Every year, humans move more earth, and more rock. More than what rivers carry with them as they rush to oceans and lakes. More than what is eroded by wind, or rain, or seasonal frictions. More than what is hurled out as lava by volcanoes. More, in fact, than all planetary forces combined. And faster, too—a few decades of human activity have displaced more materials than the planet could over millennia. This is what it means to say that humans have become a geological force, that the Earth has entered the era of the Anthropocene.

“Humans,” of course, is far too broad a descriptor to capture the causes, mechanisms, and effects of all this earthly displacement. The generic category of “human” as an agent of change only makes sense if you’re a planet. We all know that some humans—bolstered by the political systems in which they live and the institutions for which they work—are far more powerful than others. The quantity of rock moved by Anglo American in its century-plus of metal mining completely overwhelms that displaced by a migrant scraping the walls of abandoned mine shafts. But the difference is not just a matter of magnitude. More fundamentally, it’s about the inequities that enabled and conditioned this massive scalar difference, and that continue to be amplified by it. The apparent incommensurability of these scales must not blind us to their deep interdependence. This is especially evident in the use of mine waste as building material, which involves a triple extraction: of minerals, of waste, and of human health.

The increasing precarity of life on our planet may dispose us to see this use of discarded matter as an unalloyed good. Surely it’s better than removing yet more of the planet’s matter? Billions of people lack adequate shelter, after all. The need for large-scale, low-cost housing constantly outpaces its construction, as well as the availability of land to build on. The vast growth of mineral extraction since the 1940s has been accompanied by a proliferation of experiments in the re-mining of their waste products. These approaches, in turn, have relied upon—and also generated—a patchwork of modular building materials, framed by modernity’s perpetual penchant for scalability, while simultaneously containing its dark consequences. The promises of postcolonial modernity—housing, health, prosperity—tacitly assumed that these materials would be clean, abundant, and neutral: the unremarked and unremarkable means to a greater end, not sources of trouble in and of themselves. Put differently, the assumption was that the materials of postcolonial modernity were “raw”: in a state of nature, there for the taking, ready to be molded, unsullied and unaffected by previous use.

Yet many of the materials of modernity were not, in fact, inherently neutral. This was not—is not—merely a political statement. It also reflects material reality: runoff from abandoned mines, produced by the chemical reaction of exposed pyrites with oxygen, acidifies soil and water. As the ruins of mining and other industrial activity continue to spread, unchecked acid mine drainage renders ever-larger plots of land unfarmable, and ultimately unlivable. Bauxite, gold, uranium, asbestos, iron, copper, and especially coal: all generate gigantic footprints and piles of waste. No surprise, then, that these materials seduced builders, engineers, and architects. Using mine waste as a construction resource appears to address two problems at once: what to do with the waste material and land, and how to build low-cost shelter for the many thousands of workers required to run extractive processes.


Transvaal minefields photographed from hot air balloon. Photo by Eduard Spelterini, 1911. Schweizerische Nationalbibliothek, Eidgenössisches Archiv für Denkmalpflege (EAD): Sammlung Eduard Spelterini

Archaeologists have found evidence that Spanish settlers in seventeenth and eighteenth century Mexico used tailings from silver mines in building the adobe haciendas that constituted the loci of their colonial power. These buildings bear traces of the mercury used in silver amalgamation, suggesting that their erosion may have released toxins to their inhabitants. Even earlier antecedents surely exist. The reuse of mine waste is nothing new.

What has changed, however, is the scale and shape of such reuse, along with the intensity, spread, and characteristics of contamination it can generate. By 1968, when the US Bureau of Mines began sponsoring national symposia on the use of mine waste in construction, researchers and industrialists were exploring the use of waste from iron, copper, and phosphate mining, as well as fly ash (from coal), ferrous and non-ferrous scrap, and more. As one meeting chairman explained, the symposia were built on the premise that pollution and waste offered “opportunities,” whose technical and economic feasibility could be explored: “Incentives, rather than hysteria, offer a sound path toward eliminating the pollution problems of air, water, and land.” Turning waste into resource certainly seemed like the perfect industry response to the burgeoning environmental movement. Indeed, with this effort originating two years before the creation of the US Environmental Protection Agency, the mining sector appeared positively proactive.

By 1979, RILEM (now the International Union of Laboratories and Experts in Construction Materials, Systems, and Structures) reported on some twenty countries where mineral wastes supplied the formal construction industry. The largest proportion of these materials consisted of metallurgical slags and fly ash. But mine and quarry waste also contributed significantly to road construction, fill, concrete aggregates, and—in a few instances—the manufacture of bricks and plaster. The US dominated RILEM’s list, though as symposium reporters noted, this could simply be the result of more information; “in most other countries… [mine] wastes are often produced in remote areas where little attention is paid to them.” The authors noted, in passing, that “some of the mine tailings, e.g. those containing heavy metals, uranium, or asbestos may present problems of toxicity and their disposal will accordingly need to be carefully controlled.” Nevertheless, in 1979 the authors estimated that the annual production of waste rock from uranium extraction produced some 155 million tons of waste rock in the US, where some of it fed bituminous concrete aggregate. “There have been problems of radioactivity,” the authors remarked, in bloodless prose. Overall, however, they concluded that raw mine waste saw less uptake than other mineral discards, primarily because in most countries, mines “tend to occur away from populated areas and the cost of transport makes them uneconomic in comparison with competing materials.”

Construction projects located near mines and their wastes, however, don’t face the problem of transportation costs. In such instances, the economy of waste reuse could seem attractive—particularly in postcolonial states seeking a fast track to modernity. This undoubtedly drove decisions about building materials for the mining town of Mounana, Gabon, shortly after its erection in the 1970s. Each house, complete with electricity and running water, sheltered a mineworker and his family according to European nuclear family norms (no polygamists, no extended kin) and lifestyles (no chickens, no goats). In the center of town, residents could shop at the marketplace. Women delivered their babies at the maternity clinic. Children attended school. In the late 1970s, Mounana represented Gabonese “expectations of modernity” via national and corporate projects. In what appeared as a model of efficiency, waste rock from the nearby mines served as the basis for the gravel, cement, and concrete in these structures and in the paved roads that connected it with the town.

This rock, however, was not inactive. It came from the uranium shafts that powered economic activity in postcolonial eastern Gabon. The uranium content in the discarded rock was too low to extract profitably. But it was still there, and it did what uranium always does: it decayed, releasing radioactivity along the way, gradually turning into radon gas. Three decades later, and years after the mine had shut down, local activists and French NGOs found radon levels in these structures well in excess of internationally recommended limits. In the end, the mining town—which continued to lodge people after the company’s departure—had found a surefire way to make families nuclear. The materials of modernity had become instruments of slow violence.

This outcome shouldn’t have surprised the French-owned Compagnie Minière d’Uranium de Franceville (COMUF). In 1971, revelations broke that one-third of the houses in Grand Junction, Colorado were bursting with radon because they’d been built with tailings from the uranium mills that powered that town’s growth. Ninety miles further south, some homes in Uravan had radon levels over 700 times regulatory limits; subsequently abandoned, the town became a superfund site. In 1975, a survey demanded by the Navajo Tribal Council found radioactive buildings strung out from Shiprock to Tuba City. Many of these sites in the Navajo Nation remain unremediated, potent reminders of the everyday violence of the white settler state.

During the nineteenth century, hard core building—what French colonial officials called “construction en dur”—constituted a key element of the “civilizing mission.” In the colonial imagination, modernity required stone, or at least stone-based materials such as concrete or fired clay bricks. Buildings that needed seasonal maintenance to maintain their structure were coded as indigène, inferior. Europeans built solid homes in the tropics, and they assumed that their colonial subjects held the same aspirations. Throughout the mid twentieth century—including during the times of imperial decline, independence, and postcolonial possibility—the trope of the “solid house” remained a symbol of concrete modernity for many postcolonial societies seeking to build new nations.

Yet the material and economic conditions of postcolonial state-building undermined these ambitions. The ingredients of modern building were themselves exported, or taken up in the infrastructure needed for resource extraction. In making concrete, grand projects extract selected grades of sand and aggregate, quarrying them from the sum total of earthly resources. The remnants—typically degraded soils—serve as both sites and building materials for housing the global poor.

In response, new taxonomies of earthly materials and building elements emerged. Political and chemical forces concretized these taxonomies by bringing them into relation. Wartime scarcities of the 1940s coincided with experiments in sand, earth, or mud blocks, all stabilized by the addition of cement, with hybrid names such as sandcrete, landcrete, and swishcrete. Some technologies emerged from trials in American agricultural research centers, including the Tuskegee Institute, and were tested in Africa at research stations. Cement additives circumvented the need for skilled local builders and their ability to create durable structures by combining earths and organic render mixes with materials such as cow blood, urine, dung, chicken feathers, and plant fibers.

In the flush of early independences, the biggest challenges seemed to revolve around cost and scale: how to build large numbers of solid houses in which the newly franchised poor—particularly in the tropics—could live, and perhaps even thrive. The need for new houses that met acceptable standards, in the UN’s 1952 account, was staggering: 25 million homes in Latin America, homes for 100–150 million families in Asia, and enough for “just about” all the people in Africa. Rejecting Third World requests for more money—or anything that might resemble a Marshall Plan for decolonizing territories—UN experts, many of whom had previously worked for colonial governments, instead emphasized the importance of low-cost techniques and individual self-financing.

Cement-stabilized earth blocks fell neatly into this austere approach: since as much as 95% of the block volume consisted of nominally free, local, earthly material, capital reserves could be channeled to infrastructural elements such as sanitation, sheet roofing, and cement.

But there’s no such thing as a free block, and development aid always comes at a price. Consider the Landcrete press, designed in the early 1940s in South Africa by Landsborough Findlay, a company specializing in earth-moving equipment for mines and farming land. The company’s international marketing efforts succeeded: in 1953, the United Nations Korean Reconstruction Agency bought one hundred presses to help build a million homes for war refugees. As modular elements, landcrete blocks could be traded ubiquitously, from very basic production yards to housing sites. UN sponsorship of block making machines did much to displace indigenous earth building with a fragmented and interchangeable vision of building, couched in the idea of “self-help” in international “development.” And as M. Ijlal Muzaffar documents, the “participating native” was a central figure in this discourse, which unabashedly celebrated “traditional” building techniques and indigenous “ingenuity”—even as it worked to supersede local expertise—all the while claiming to represent “the demands and desires of populations already in transition to modernity.” As presses such as the Landcrete (which had many successors and spin-offs) gained traction in international development circles, blocks replaced solid earth in the building envelope. In the same years that Western photographers began training their cameras on the marvels of indigenous earth architectures, “development” agencies and technical experts worked to fracture their integrity.

Cheap blocks complemented the “roof loan” approach, conceived by UN technical advisors on housing. Working in the Gold Coast, the American housing advocate Charles Abrams, along with Vladimir Bodiansky and Otto Koenigsberger imagined that community savings groups would share loans to buy industrially produced materials to roof the houses with already completed walls, which they had built with cheap or personal labor from locally made earth blocks. Rather than evolving together, then, roofs and blocks were recombined in the “self-help” house as elements with diverse procurement paths. Block fabrication could now take place before or beyond the oversight of technical experts, while the roof materials were locked in place through debt.

In this plan, good roofs allowed for bad walls. Protected by the overhang of a relatively durable roof, supported by a sanitary core and pillars, stabilized earth blocks did not have to meet any standards of longevity, size, material, or even delivery timelines. By the 1960s, the roof loan scheme—originally designed to conclude the self-housing process—became instead its starting point. This inversion allowed experts to abandon recipients, leaving them to finish their homes entirely by themselves, while repaying the roof loan to their community savings group.

Roof loans also opened the market for both asbestos cement and corrugated aluminum roofs, along with corrugated iron. Their specification related to the availability of raw materials, all of which generated potentially toxic residues and landscapes. In Ghana, for instance, the Volta Aluminium Company began construction on an aluminum smelter in 1964, with the view to make construction products from its bauxite ore mines. In South Africa—with its rich reserves of asbestos, iron ore, and strip-mined coal—asbestos-cement roofs and corrugated iron split the market. In both countries, such beneficiation of raw materials made some economic sense. But for countries without minerals, importing any of these materials represented a burden.

In this assemblage of debt, roof, and unfinished walls, waste served as a basic material for cheap, locally made blocks. Discarded material could substitute for good earth, ideally leaving it as soil for farming. Co-locating housing with borrow pits and other “drosscapes” made discards readily available as construction material. In countries with mineral resources, low cost housing near mines and mills would use materials created as by-products in industrial processes, including red mud from bauxite tailings from alumina extraction, as well as tailings from zinc, copper, gold, asbestos, uranium, and iron mines. Portland cement, the ubiquitous stabilizing material, itself was mixed with wastes, including lime sludges, slags, and fly ash.

The consequences of this regulatory arbitrage around mining wastes in building materials are rarely documented. One exceptional study, however, assessed the risk of exposure to dangerous fibers around former asbestos mining sites in South Africa, and then trained villagers to collect samples from houses and schools built from local blocks.


Asbestos waste in locally made blocks used for a house in Sedibeng village, near Kuruman, South Africa. Photo by Asbestos Interest Group community monitors, 2019.

Their focus was on those structures that might contain materials gleaned from nearby tailings in the blocks, floors, and plaster. Of thirty-one sites surveyed in the village of Sedibeng, near the mining center of Kuruman, 88% of blocks, 94% of houses, and the only school contained asbestos containing building materials (ACBM), some in friable blocks that could release fibers into their surroundings. In impoverished communities where many elders had contracted fatal mesotheliomas working in now abandoned mines and closed mills, this risk lingers for another generation. Another brick in the crumbling wall of wasted modernity.

In 2019, we travelled the length of the Main Reef Road, which stretches both east and westwards from Johannesburg. Built to serve the industrial gold mines that spawned the city, the road spans much of South Africa’s Witwatersrand plateau, known by the same moniker as its currency: the Rand. We wanted to sample the range of blocks—along with their constituent materials—that people can buy to build or expand their homes. How, we wondered, do current residents of the Rand create homes in toxic wastelands, especially in the absence of adequate state housing and land remediation programs?

Launched in 1886, the Rand’s mines rapidly became the deepest in the world. Removing “overburden” to reach gold seams, miners extracted billions of tons of rock, formed into gigantic tailing piles and vast slime dams that comprehensively transformed the region’s topography in just a few decades. By 1911, fifty-two mines formed a nearly 100-kilometer band from Randfontein to Nigel. As their tailings dumps continued to grow, they also became more dangerous. The cyanide leaching of ore to recover gold required milling the ore more finely, which produced smaller dust particles that were even more mobile and inhalable. The leaching itself produced vast quantities of sludge that was dumped into the seasonal waterpans of the lowest-lying areas, whence it leaked into streams and groundwater.

Today, some 1.6 million people live on or very near toxic mine dumps, mostly in former black townships and informal settlements, often in precarious conditions. Heavy metals—in no short supply thanks to the dumps and their dust—dissolve readily in the highly acidic water that decants from mine shafts, transporting toxicants such as mercury, arsenic, and lead into groundwater, streams, and farmland. Uranium-laced dust whips into homes and settles on the vegetable patches that residents rely on for sustenance.

Over the course of recent decades, mining companies (ever-morphing into new ownership structures) have moved this patchwork of tailings, reprocessing them for gold and/or uranium before reassembling remaining waste into three superdumps. Water and surface damage form the residual footprints of removed dumps.

Urban planners, municipalities, and provincial authorities continue to imagine this toxified landscape as a vacant space to meet South Africa’s perpetual “housing problem.” In the 1940s, Landcrete—which pressed out solutions to surplus mine sand, abandoned land, and the cost of building materials in a single mechanism, powered by cheap labor—came out of this very landscape. Buildings on the Witwatersrand still amalgamate these elements, albeit at a far greater scale.

Right now, five thousand “affordable” housing units are being built as a flagship project on land cleared by the removal of a dump at Fleurhof, just north of Soweto. But faced with long waiting lists, unhoused residents—no longer willing to accept cramped backroom housing or makeshift informal settlements—have taken construction into their own hands. Inevitably, given both the urgency of housing penury and the lack of state capacity, such building happens without regulatory oversight.

In altering existing houses, residents often remove their asbestos-cement roofs, either reusing whole sheets or dumping broken ones in nearby parks and open dumpsites, where they continue to fragment and crumble into deadly fibers. Builders use blocks from nearby roadside brick makers, who in turn collect sand and additional materials from mine residues and other sources of solid waste.

Near KwaThema, a woman sold us some crumbling, pinkish blocks that contained sand gathered from the low-lying residues of dumps that had been removed for industrial-scale reprocessing. Further out on the Main Reef Road, we found an enterprising man making blocks from a dark, sticky gravel that looked like incinerator waste. Operations like his abounded.


Informal gold digger, disused Western Holdings mine, Welkom, Free State. Gold bearing gravel is unloaded near a polluted sewerage canal. Photo by Ilan Godfrey, 2012.

Closer to Johannesburg, over the Main Reef road from Fleurhof, we located a small blockmaking business run by an elderly, weather-worn Afrikaner with a half-dozen employees. Just a few hundred meters downhill from this operation, on the lip of a large abandoned mine cavity, young artisanal “zama-zama” miners from Zimbabwe and Lesotho had established a basecamp, where they dug around and into the abandoned pits, scavenging rock with potential gold content. Block and mining businesses share a crusher belt—and, apparently, the occasional braai. The Afrikaner and his staff fashion their ground rock into blocks, which they mainly sell to clients from Soweto. The zama-zamas put their ground rock through an artisanal treatment process, most likely using mercury to suspend any gold. Three or four times a week, the police swing by to collect their cut, which explained stern injunctions from both groups to refrain from taking pictures.

Each batch of blocks differs in its exact composition, but all include the toxic remainders of mining. Sold in small loads to backyard builders, they redistribute these residues into residences. Following the precise paths of these many relocations would be nearly impossible. Regulation, in such situations, isn’t even the subject of reverie. Utterly unremarked, this new configuration of “self-help” compresses toxic landscapes into the framework of the home. Extraction removes the good earth. The poor inherit the bad earth. They live on it, and in it, and with it. To be sure, there is some bad earth in all of us. But bad earth does its worst in the bodies and homes of those who struggle most for daily survival.

By Hannah le Roux and Gabrielle Hecht

Hannah le Roux is an architect, educator and theorist. She is Associate Professor at University of the Witwatersrand, Johannesburg.

Gabrielle Hecht is the Frank Stanton Foundation Professor of Nuclear Security at the Center for International Security and Cooperation at Stanford University, where she is also Professor of History, Professor (by courtesy) of Anthropology, and Senior Fellow at the Freeman Spogli Institute.


Source: e-flux architecture



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