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Stone has the potential to become the low-carbon structural material of choice, but barriers to quarrying and a lack of awareness must be overcome to achieve this, experts told Dezeen in a Stone Age 2.0 feature.
Paola Blasi, a geologist at Arup who advises architects on how to use stone, says the material is finally back in the structural lexicon due to its low carbon footprint.
“The structural use of stone is not new,” Brasi said. “People are talking about the embodied carbon of materials, and stone is coming into that topic because, in effect, the material has zero embodied carbon—you cut it and you’re done.”
Architect Amin Taha, who designed the structural stone architecture of the 15 Clerkenwell Close building, agreed, adding that the material was becoming increasingly popular because it was less expensive than steel and concrete. Materials can significantly save carbon emissions.
“Concrete and steel suppliers and engineers are talking about ‘green’ versions of both, but if all the energy and material savings were coordinated, in the best case they could save 40% of the embodied carbon content of stone. Still 98% lower, even with diesel-powered cutting equipment,” Taha told Dezeen.
“As the French government requires its quarries to use renewable energy, the carbon content of the stone is almost zero,” he continued.
However, despite its potential to reduce carbon emissions, the material is not commonly used as a modern building material.
According to experts, one of the main reasons for this is the debate over the availability of stone and the quarrying process.
“It’s generally accepted that there are no more rocks”
While architect Elisabeth Polzella believes that large quantities of stone could be mined by opening more quarries, researcher Natalia Petkova believes that these sites must be carefully assessed and planned.
“There is a common belief that there is no stone left, but there was a lot of stone when it was built,” Polzella said.
“quarrying is very expensive, difficult and takes a long time. [but] The policy should be to allow more quarries to be opened. “
For Petkova, however, the idea that stone is an “infinite material” is misleading.
“In absolute terms, that’s true, but in practice there are a lot of limitations,” she told Dezeen in an interview.
She explains that the proximity of the quarry to the construction site is important if the material is to be used sustainably.
“Research conducted by ETH Zurich shows that if stone is transported by truck for more than 200 kilometers, it may no longer make sense to use it structurally to reduce carbon emissions,” Petkova said.
“There are also political and artificial constraints, such as people not wanting new quarries in residential areas. These attitudes can certainly develop, but it’s not a given.”
“Stone must be selected and purchased correctly”
Other experts worry about the amount of waste produced by the quarry, as well as changes in the color and texture of the stone, which are difficult to predict before mining.
Stonemason Pierre Bidaud said: “Stone is extremely expensive due to the ‘visual impairment’ of certain stones.”
“For the past 10 or 15 years, France has been using stone as a load-bearing facade system because they use a full range of stone – they do as little work as possible on the stone to avoid high costs and energy.”
“If a quarry is not properly equipped, a lot of waste is produced and a lot of material is destroyed, which affects the carbon content of the stone,” Brasi added.
“It’s not enough to just say use stone, the stone must be properly selected and sourced.”
While changes in stone samples may be an aesthetic issue, it also raises concerns about changes in structural performance.
Brasi explained that proper identification and testing of the stone will make it easier to use in the construction industry. Through this, she claims, it will “increase people’s trust in building materials”.
Although stone building products in Europe are required to obtain the CE mark (which states that the material has been tested for porosity, absorbency, flexural and compressive strength, etc.), and products in the UK are also required to obtain the UKCA mark, Blasi claims that not all quarried stone The venues comply with European standards. Europe is testing their products properly.
“In the past, people were hesitant because stone is a natural material and can vary greatly from sample to sample,” she explains. “The biggest leap for me was convincing quarries and manufacturers to describe their products carefully.”
“We need to reassure engineers because they think stone is a difficult material to be sure natural materials are not failing or cracking,” Bideau agrees.
“The next biggest hurdle will be procurement”
Taha believes that direct communication with stone suppliers and a better understanding of the material will increase its popularity as a structural building material and lead to “lower costs, negative carbon emissions and better buildings”.
“Aside from educational consultants, the next biggest hurdle will be procurement,” he said.
“We have a properly risk-averse industry and the triumvirate of project managers, quantity surveyors and contractors come up with yet another circular argument, ‘what was right yesterday will be right tomorrow’, and even worse is ‘leaving the main contractor Set costs and then take turns setting costs. Market’.”
“This limits the scope for innovation, fails to save customers construction costs, and inevitably leads to a business-as-usual approach as we all strive to reduce carbon emissions,” Taha said.
“We believe this will become the new CLT in the stone industry”
Bidaud believes prefabricated structural stone will make the material a popular choice among architects.
As creative director of construction company The Stonemasonry Company, he has been putting this idea into practice, aiming to prove that stone can be quickly assembled on construction sites.
“We can’t do traditional construction on site like we did 70 years ago, using wet methods, mortars and so on,” Bidaud said.
“We are 20 years behind cross-laminated timber [CLT] And the timber revolution,” he added. “Only now are we starting to see architects questioning the use of stone, no longer using it as a veneer but instead using it as a load-bearing material – proposing what CLT has done over the past 20 years as a prefabrication and refinement The system has been in place for many years.”
“At The Stone Masonry Company, we seek to speed up on-site progress with our reinforced and prefabricated natural stone systems.”
Stonemasonry collects waste rock from quarries that is discarded due to changes in color and texture and reuses it by manufacturing prefabricated components.
The discarded blocks are cut into smaller pieces to make it easier for engineers to check their suitability. Drill holes into them and run cables or metal rebar through them to connect them to prefabricated building elements.
Bidaud said the prefabricated elements can be made into walls up to 5 square meters in size, 500 mm columns up to 6 meters high, and also into floor slabs.
“We believe this will become the new CLT in the stone industry,” he said.
Looking back at how stone has been sourced historically, experts say spolia – a Latin term that describes the removal of stone structures to be reused in new construction – is enjoying a resurgence.
“One building becomes a quarry for another”
Used in ancient times due to the amount of work involved in cutting and carving new stone, today its appeal is driven by the carbon cost-effectiveness of reusing stone rather than mining more raw material.
“Romano-Gothic and Renaissance builders demolished stone buildings to reuse and rebuild other stone buildings—a virtuous cycle,” Bido explains.
“One building becomes a quarry for another building,” Porzella added.
Robert Greer, director of stone and restoration contractor Paye Stonework, said there had been a “significant increase” in the demolition of stone buildings for reuse in the past five years.
This is sometimes caused by the inability to obtain new stone, whether due to legislative restrictions or limited quarry resources.
Greer describes London in particular having seen an increase in sporadic numbers over the past five years, largely due to changes in planning policy that encourage the circular economy and reuse materials in their best form.
“Most of the proposed schemes are in central London and meet the requirements of London planning policy, but because the technology to survey existing stone now allows us to scan the depth of individual stones, we are able to work out the volume of the stone to reuse as structural stone or Cladding,” Greer said.
“It’s really grown exponentially, whether it’s a trojan horse to meet planning requirements and get development through the system, or really serious about recognizing that there’s a material out there that has good value and can be repurposed, reused and at its best. “
“Knowledge has improved, production costs have gone down, and at the same time, people have realized that stone is a resilient, solid material that can actually be reused — it’s not permanent like concrete,” Greer said.
“There’s a lot of talk about deconstruction right now”
Petkova believes that demolishing stone buildings is not without carbon costs. To her, the longevity and durability of stone make it a more sustainable material.
“There’s a lot of talk about deconstructing and reusing individual building components, but the process still requires energy,” she said.
“Solid stone construction speaks more to the idea of permanence and reuse of the entire building,” Petkova continued. “This means designing a building that is not only durable in terms of material, but also potentially durable over a long period of time.” remain culturally relevant.”
The above photo was taken by Paola Blasi.
Stone Age 2.0
This article is part of Dezeen’s Stone Age 2.0 series, which explores the potential of stone as a viable, low-carbon, modern structural material.
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