There is, in the built environment, a trend towards single-purpose buildings. The companies that commission them love them because they are designed with a specific use in mind. Architects, meanwhile, hate them.
In an interview with architecture magazine Dezeen, 2019 Royal Institute of British Architects Royal Gold Medal winner Nicholas Grimshaw speaks out against what he refers to as handbag architecture. ‘Handbag architecture is when, say, a client has a choice of models of building – like six in a row on a shelf – and they just choose one,’ he says. ‘There’s no depth to the discussion. They’re doing it entirely on visual means, like choosing a coffee pot or something.’
Grimshaw says he was determined to think deeper about built spaces that have more than one use over their lifespan. ‘Especially if you consider the reuse and recycling of them,’ he tells Dezeen. ‘Very often these handbag architecture buildings are only any use [in terms of] what they’re first designed for. Nobody knows what the hell to do with them afterwards.’
As a result, those buildings are invariably knocked down and replaced (perhaps with another handbag), leaving piles of rubble behind during the demolition and construction processes. He argues that those piles are unnecessary. ‘I think the most destructive thing is to demolish a building, get rid of all the demolished material, and then build another one – when with a bit of real design ingenuity you can make an existing building work anew for something else.’
Looking at those piles and piles of builders’ rubble – generated from both construction and demolition waste – that clog up SA’s landfills, it’s hard to disagree with him. According to research by the Western Cape green economy NPO GreenCape, about 85% of builders’ rubble – that’s the mineral component, made up of masonry, old concrete, steel, bricks, sand and so on – is landfilled in SA, despite its significant reuse potential as a secondary material.
Meanwhile, the National Waste Information Baseline report estimates that, of the 4.7 million tons of builders’ rubble generated in SA in 2012, just 0.7 million tons were recycled. The rest – all 4 million tons of it – was landfilled. Compounding the problem, vast quantities of construction and demolition waste don’t even make it to landfill, instead ending up being illegally dumped by construction teams who don’t know or couldn’t be bothered to figure out what else to do with it.
In a 2018 interview with the Pretoria East Rekord, City of Tshwane mayoral spokesperson Samkelo Mgobozi warns that the city is running out of space for landfill sites, adding that ‘illegal dumping – mostly building rubble or construction waste – is also an issue throughout various parts of Pretoria’. At the same time, the municipality started offering R3 000 rewards for information that would lead to the successful prosecution of people responsible for illegally dumping building rubble.
The City of Johannesburg also revealed that it spends around R170 million a year cleaning up street litter and illegal dump sites, with Muzi Mkhwanazi – a spokesperson for Pikitup, the City’s official integrated waste management service provider – telling the Saturday Star that illegal dumping constituted an average of 284 659 tons per year in the city. ‘It presents in many forms and at varying degrees per area,’ says Mkhwanazi. ‘However, builders’ rubble constitutes significant tonnages of illegal dumping waste composition.’
This is echoed by the City of Cape Town’s Integrated Waste Management Plan, which estimates that 34% of the city’s illegally disposed waste is made up of builders’ rubble – second only to domestic waste (49%). Meanwhile, research by the CSIR puts the percentage of municipal waste composition (by mass) of builders’ rubble at 22% in Cape Town and 20% in Gauteng.
GreenCape’s 2016 industry brief on builders’ rubble notes that ‘based on international experience, the biggest opportunities in the recovery, processing and application of builders’ rubble lie in road building. There are opportunities both on the supply side for the crushing industry, as well as on the demand side in road construction for the public and private sectors’. This is borne out by local industry leader Ross Demolition, which recycles 98% of the rubble generated in its demolition projects. Using state-of-the-art crushing equipment, Ross Demolition is able to clean clay bricks for reuse, process concrete into bricks, and provide crushed material for use as sub-base to build roads.
Cape Town is a useful case study. Using data provided by the City of Cape Town, GreenCape reports that about 518 000 m3 (at an average of 43 200 m3 per month) is landfilled every year in the city, even though 25% of that material could be used in road construction, 30% in foundations and road embankments, and about 20% in fill. In other words, GreenCape estimates, ‘an extra 11 400 m3 per month of high-quality material, with a value of R1.1 million to R1.5 million, could be available to the market for sub-base material in road construction in the City of Cape Town’
There are currently four main applications of builders’ rubble: as backfill (to fill up holes); as landfill cover, slope stabilisation or building material for landfill roads; as road base and foundation; and as re-concreting, where concrete is crushed and re-entered into the ready-mix or precast concrete processes. That fourth application is far more sensitive than the others and requires a higher quality of rubble. For that reason, while GreenCape notes ‘a growing recognition that builders’ rubble is a useful and cheaper construction material that offers the same performance as virgin materials’, it stresses that there has to be adequate quality control over the materials used.
That’s also why many local crushing companies insist that the material entering their processing facilities must be ‘pure’ – or devoid of material other than builders’ rubble. Many construction and demolition sites do not separate at source, though, which means that their rubble cannot be isolated and sent to processors. It then, more often than not, ends up in landfill. But there’s value in that rubble – and building is an expensive business.
The price of virgin material has grown faster than inflation, with GreenCape estimating that the average building costs in the Western Cape increased from about R4 400 per m2 in 2011 to approximately R6 600 per m2 in 2015. Material costs make up about 50% of the total building cost, while aggregate (G2, G7 and fill) and cement account for about 16.5% and 15% respectively of the average material use. ‘Considering the price of recovered material is cheaper than virgin material, this provides a more attractive business case for investors looking to meet a growing demand for cheaper structures,’ GreenCape notes in its 2018 Waste Market Intelligence report.
So far, the smaller local contractors have been quickest on the uptake when it comes to using secondary materials. The reasons for this are cost-related. Smaller operations feel economic pressures more keenly than larger companies, so they’re attracted by the cost and material benefits of builders’ rubble. However, according to GreenCape, ‘due to the lower prices and performance of secondary material compared to virgin material, larger companies are now also actively participating in the builders’ rubble market’.
The same report warns, though, that ‘the economy in builders’ rubble must be considered at a regional scale, due to the low value of the material relative to handling and transport costs. Economic viability is therefore dependent on local supply and processing of materials, so that the transport and processing costs do not exceed the market value of the material’. On one hand, then, SA has the issue of overflowing landfills and illegal dumping; on the other, there’s the move towards greener, more sustainable and more cost-effective building practices.
A 2017 study by Bulent Ecevit University in Turkey points out that the ‘advantages of recycling [builders’ rubble] are extensive: conservation/preservation of precious land areas; extension of the lifespan of landfills; cost effectiveness of using recycled products, improvement of general environmental status in terms of energy and pollution; minimisation of the resource consumption; utilisation of waste that would otherwise be lost to landfill sites; and job creation’.
Recycled builders’ rubble presents a clear opportunity, then – and indeed, the idea of re-using construction and demolition waste is not a new one. A 2008 EU directive set a minimum target of reuse, recycling and material recovery of non-hazardous construction and demolition waste at 70% by weight until 2020. By 2017, according to research by Bulent Ecevit, only five EU states had reached that target: the Netherlands (98.1%), Denmark (94.9%), Estonia (91.9%), Germany (86.3%) and Ireland (79.5%). Meanwhile, in the US, 73.5% of construction and demolition waste is recovered, with a 35% recycling rate for mixed rubble, 85% for bulk aggregate and more than 99% for reclaimed asphalt pavement.
In SA, Operation Phakisa aims to increase the demand for secondary material builders’ rubble by requiring 30% of recycled construction materials to be used for buildings and roads. While the exact figures are still under discussion, the move is certainly in line with international best practice. And, if nothing else, the reuse of builders’ rubble should provide some relief to the people who have to live with illegal dumping, and to the builders or demolition teams who’re left with piles of bricks, sand and concrete, and who aren’t quite sure what to do with them.