̽��ֱ�� of Cambridge - concrete

Cement recycling method could help solve one of the world’s biggest climate challenges

sc604 — Wed, 22 May 2024 14:47:38 +0000

Researchers from the ̽��ֱ�� of Cambridge have developed a method to produce very low-emission concrete at scale – an innovation that could be transformative for the transition to net zero.

Cambridge researchers help develop smart, 3D printed concrete wall for National Highways project

sc604 — Thu, 13 Jul 2023 12:01:02 +0000

̽��ֱ��3D-printed structure – a type of retaining wall known as a headwall – has been installed on the A30 in Cornwall, where it is providing real-time information thanks to Cambridge-designed sensors embedded in its structure. ̽��ֱ��sensors provide up-to-date measurements including temperature, strain and pressure. This ‘digital twin’ of the wall could help spot and correct faults before they occur.

Headwall structures are normally made in limited shapes from precast concrete, requiring formwork and extensive steel reinforcement. But by using 3D printing, the team – including specialists from Costain, Jacobs and Versarien – could design and construct a curved hollow wall with no formwork and no steel reinforcement. ̽��ֱ��wall gets its strength not from steel, but from geometry instead.

̽��ֱ��wall – which took one hour to print – is roughly two metres high and three and a half metres across. It was printed in Gloucestershire at the headquarters of the advanced engineering company Versarien, using a robot arm-based concrete printer. Making the wall using 3D printing significantly saves on costs, materials and carbon emissions.

Over the past six years, Professor Abir Al-Tabbaa’s team in the Department of Engineering has been developing new sensor technologies and exploring the effectiveness of existing commercial sensors to get better-quality information out of infrastructure. Her team has also developed various ‘smart’ self-healing concretes. For this project, they supplied sensors to measure temperature during the printing process.

Temperature variations at different layers of the 3D-printed wall were continuously monitored to detect any potential hotspots, thermal gradients, or anomalies. ̽��ֱ��temperature data will be correlated with the corresponding thermal imaging profile to understand the thermal behaviour of the 3D-printed wall.

“Since you need an extremely fast-setting cement for 3D printing, it also generates an enormous amount of heat,” said Al-Tabbaa. “We embedded our sensors in the wall to measure temperature during construction, and now we’re getting data from them while the wall is on site.”

In addition to temperature, the sensors measure relative humidity, pressure, strain, electrical resistivity, and electrochemical potential. ̽��ֱ��measurements provide valuable insights into the reliability, robustness, accuracy, and longevity of the sensors.

A LiDAR system also was used to scan the wall as it was being printed to create a 3D point cloud and generate a digital twin of the wall.

“Making the wall digital means it can speak for itself,” said Al-Tabbaa. “And we can use our sensors to understand these 3D printed structures better and accelerate their acceptance in industry.”

̽��ֱ��Cambridge team developed a type of sensor, known as a PZT (Piezoceramic Lead-Zirconate-Titanate) sensor, which measures electromechanical impedance response and monitors changes in these measurements over time to detect any possible damage. These smart sensors can show how 3D-printed mortar hardens over time, while simultaneously monitoring the host structure’s health.

Eight PZT sensors were embedded within the wall layers at different positions during the 3D printing process to capture the presence of loading and strain, both during the construction process and service life after field installation.

̽��ֱ��team, which included experts in smart materials, automation and robotics and data science, also developed a bespoke wireless data acquisition system. This enabled the collection of the multifrequency electromechanical response data of the embedded sensors remotely from Cambridge.

“This project will serve as a living laboratory, generating valuable data over its lifespan,” said Al-Tabbaa. “ ̽��ֱ��sensor data and ‘digital twin’ will help infrastructure professionals better understand how 3D printing can be used and tailored to print larger and more complex cement-based materials for the strategic road network.”

Members of the team included Dr Sripriya Rengaraju, Dr Christos Vlachakis, Dr Yen-Fang Su, Dr Damian Palin, Dr Hussam Taha, Dr Richard Anvo and Dr Lilia Potseluyko from Cambridge; as well as Costain’s Head of Materials Bhavika Ramrakhyani, a part-time PhD student in the Department of Engineering, and Ben Harries, Architectural Innovation Lead at Versarien, who is also starting a part-time PhD in the Department of Engineering in October.

̽��ֱ��Cambridge team’s work is part of the Resilient Materials for Life Programme and the Digital Roads of the Future Initiative. ̽��ֱ��research is supported in part by the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI), and the European Union.

Cambridge researchers, working in partnership with industry, have helped develop the first 3D-printed piece of concrete infrastructure to be used on a National Highways project.

Making the wall digital means it can speak for itself, and we can use our sensors to understand these 3D-printed structures better and accelerate their acceptance in industry

Abir Al-Tabbaa

Cool Concrete – the smart, 3D printed concrete wall used for National Highways project.

National Highways

3D printed retaining wall

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Opinion: Dreaming big with biomimetics: could future buildings be made with bone and eggshells?

Anonymous — Wed, 09 Mar 2016 12:41:18 +0000

As the world grapples with climate change, we urgently need to find ways of reducing our CO₂ emissions. Sectors which rely heavily on fossil fuels, such as energy and aviation, are commonly held to be the worst offenders. But what most people don’t realise is that there’s another culprit, hiding in plain sight; on the streets of our cities, and in the buildings where we live and work.

In 2007 alone, steel and concrete were each responsible for more CO₂ emissions than the entire global aviation industry. Before reaching the construction site, both steel and cement must be processed at very high temperatures – and this takes a lot of energy. So how can we reduce our dependence on these “dirty” materials, when they play such a crucial role in construction?

One option is to use natural materials, such as wood. Humans have been building with wood for thousands of years, and wooden structures are currently experiencing a minor resurgence – partly because it’s a cheap and sustainable material.

But there are some disadvantages to building with wood; the material can warp in humid conditions, and is susceptible to attack by pests such as termites. And while natural materials, such as wood, are appealing from an environmental perspective, they can be unsatisfying for engineers who might wish to make components in a specific shape or size.

Copying life

So what if, instead of using natural materials as we find them, we make new materials that are inspired by nature? This idea started to gain traction in the research community in the 1970s and really exploded in the 1990s, with the development of nanotechnology and nanofabrication methods. Today, it forms the basis of a new field of scientific research: namely, “biomimetics” – literally “copying life”.

Biological cells are often referred to as “the building blocks of life”, because they are the smallest units of living matter. But to create a multi-cellular organism like you or me, cells must clump together with a support structure to form the biological materials we’re made of, tissues such as bone, cartilage, and muscle. It’s materials like these, which scientists interested in biomimetics have turned to for inspiration.

In order to make biomimetic materials, we need to have a deep understanding of how natural materials work. We know that natural materials are also “composites”: they are made of multiple different base materials, each with different properties. Composite materials are often lighter than single component materials, such as metals, while still having desirable properties such as stiffness, strength and toughness.

Making biomimetic materials

Materials engineers have spent decades measuring the composition, structure and properties of natural materials such as bone and eggshell, so we now have a good understanding of their characteristics.

For instance, we know that bone is composed of hydrated protein and mineral, in almost equal proportions. ̽��ֱ��mineral confers stiffness and hardness, while the protein confers toughness and resistance to fracture. Although bones can break, it is relatively rare, and they have the benefit of being self-healing – another feature that engineers are trying to bring to biomimetic materials.

Like bone, eggshell is a composite material, but it is around 95% mineral and only 5% hydrated protein. Yet even that small amount of protein is enough to make eggshell very tough, considering its thinness – as most breakfast cooks will have noticed. ̽��ֱ��next challenge is to turn this knowledge into something solid.

There are two ways to mimic natural materials. Either you can mimic the composition of the material itself, or you can copy the process by which the material was made. Since natural materials are made by living creatures, there are no high temperatures involved in either of these methods. As such, biomimetic materials – let’s call them “neo-bone” and “neo-eggshell” – take much less energy to produce than steel or concrete.

In the laboratory, we have succeeded in making centimetre-scale samples of neo-bone. We do this by preparing different solutions of protein with the components that make bone mineral. A composite neo-bone material is then deposited from these solutions in a biomimetic manner at body temperature. There is no reason that this process – or an improved, faster version of it – couldn’t be scaled up to an industrial level.

Of course, steel and concrete are everywhere, so the way we design and construct buildings is optimised for these materials. To begin using biomimetic materials on a large scale, we’d need to completely rethink our building codes and standards for construction materials. But then, if we want to build future cities in a sustainable way, perhaps a major rethink is exactly what’s needed. ̽��ֱ��science is still in its infancy, but that doesn’t mean we can’t dream big about the future.

Michelle Oyen, Reader in Bioengineering, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

̽��ֱ��opinions expressed in this article are those of the individual author(s) and do not represent the views of the ̽��ֱ�� of Cambridge.

Michelle Oyen (Department of Engineering) discusses how we could reduce our dependence on "dirty" materials like steel and concrete.

James Royal-Lawson

A tray of eggs up close

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Health-conscious concrete

lw355 — Mon, 23 Mar 2015 12:10:47 +0000

Skin is renewable and self-repairing – our first line of defence against the wear and tear of everyday life. If damaged, a myriad of repair processes spring into action to protect and heal the body. Clotting factors seal the break, a scab forms to protect the wound from infection, and healing agents begin to generate new tissue.

Taking inspiration from this remarkable living healthcare package, researchers are asking whether damage sensing and repair can be engineered into a quite different material: concrete.

Their aim is to produce a ‘material for life’, one with an in-built first-aid system that responds to all manner of physical and chemical damage by self-repairing, over and over again.

Self-healing materials were voted one of the top-ten emerging technologies in 2013 by the World Economic Forum, and are being actively explored in the aerospace industry, where they provide benefits in safety and longevity. But perhaps one area where self-healing might have the most widespread effect is in the concrete-based construction industry.

Concrete is everywhere you look: in buildings, bridges, motorways, and reservoir dams. It’s also in the places you can’t see: foundations, tunnels, underground nuclear waste facilities, and oil and gas wells. After water, concrete is the second most consumed product on earth; tonne for tonne, it is used annually twice as much as steel, aluminium, plastic and wood combined.

But, like most things, concrete has a finite lifespan. “Traditionally, civil engineering has built-in redundancy of design to make sure the structure is safe despite a variety of adverse events. But, over the long term, repair and eventual replacement is inevitable,” said Professor Abir Al-Tabbaa, from the Department of Engineering and the lead of the Cambridge component of the research project.

̽��ֱ��UK spends around £40 billion per year on the repair and maintenance of existing, mainly concrete, structures. However, repairing and replacing concrete structures cause disruptions and contribute to the already high level of carbon dioxide emissions that result from cement manufacturing. What if the life of all new and repaired concrete structures – and in fact any cement-based material, including grout and mortar – could be extended from an average of several decades to double this, or more, through self-healing?

In 2013, researchers in Cambridge joined forces with colleagues at the Universities of Cardiff (who lead the project) and Bath to create a new generation of ‘smart’ concrete and other cement-based construction materials.

“Previous attempts in this field have focused on individual technologies that provide only a partial solution to the multi-scale, spatial and temporal nature of damage,” explained Al-Tabbaa. By contrast, this study, funded by the Engineering and Physical Sciences Research Council, provides an exciting opportunity to look at the benefits of combining several ‘healthcare packages’ in the same piece of concrete.

“Like the many processes that occur in skin, a combination of technologies has the potential to protect concrete from damage on multiple scales – and, moreover, to do this in a way that allows ‘restocking’ of the healing agents over time,” she added.

Mechanical damage can cause cracks, allowing water to seep in; freezing and thawing can then force the cracks wider. Loss of calcium in the concrete into the water can leave decalcified areas brittle. And, if fractures are deep enough to allow water to reach the reinforcing steel bars, then corrosion and disintegration spell the end for the structure.

̽��ֱ��team in Cambridge is addressing damage at the nano/microscale by developing innovative microcapsules containing a cargo of mineral-based healing agent. It’s like having a first-aid kit in a bubble: the idea is that physical and chemical triggers will cause the capsules to break open, releasing their healing and sealing agents to repair the lesion.

“While various cargo and shell materials have been developed for other applications, from food flavouring and pharmaceuticals to cosmetics and cleaning products, they are not generally applicable to cement-based matrices and are far too expensive for use in concrete, which is why we have needed to develop our own,” explained Al-Tabbaa.

Another challenge is to make sure the capsules will be strong enough to withstand being mixed in a cement mixer, yet fragile enough to be broken open by even the smallest of fractures. Innovative capsule production techniques are being investigated that can be scaled up to deliver the huge volumes of capsules required for use in construction.

In parallel, the team in Bath is investigating healing at the mid-range micro/mesoscale with spore-forming bacteria that act as tiny mineral-producing factories, feeding on nutrients added to the cement and facilitating calcite precipitation to plug the cracks in the concrete. Different techniques for housing and protecting the bacteria and nutrients within the cement matrix are being investigated, including the capsules that are being developed at Cambridge.

̽��ֱ�� ̽��ֱ�� of Cardiff researchers are engineering ‘shape memory’ plastic tendons into the cement matrix to close large cracks at the larger meso/macroscale through triggering of the shrinkage of the tendons by heat.

̽��ֱ��project team are then collectively addressing repeated damage through the creation of vascular networks of hollow tubes, like the circulatory system of a living organism, so that self-healing components can continually be replenished.

As the Cambridge researchers move closer to the best formulations for the microcapsules, they have begun collaborating with companies who can scale up the production to the levels required to seed tonnes of cement. Meanwhile, the three research groups are also beginning to test combinations of each of their techniques, to find the best recipe for maximum self-healing capability.

By the summer of 2015, with the help of industrial partners, field trials will test and refine the most promising combined systems in a range of real environments and real damage scenarios. This will include testing them in non-structural elements in the Department of Engineering’s new James Dyson Building.

“This is when it will become really exciting,” said Al-Tabbaa. “To be truly self-healing, the concrete needs to be responsive to the inherently multi-dimensional nature of damage, over long time scales. We want concrete to be a material for life that can heal itself again and again when wounded.”

Inset image: concrete microcapsules, credit Chrysoula Litina.

Roads that self-repair, bridges filled with first-aid bubbles, buildings with arteries… not some futuristic fantasy but a very real possibility with ‘smart’ concrete.

We want concrete to be a material for life that can heal itself again and again when wounded.

Abir Al-Tabbaa

Tanvir Qureshi

Healing material released when concrete microcapsules burst open

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Better building through design

sc604 — Wed, 04 Jun 2014 08:16:01 +0000

̽��ֱ��construction industry, which uses half of the 1.5 billion tonnes of steel produced each year, could drastically reduce its carbon footprint by optimising the design of new buildings. Smart design could slash the sector’s carbon emissions by around 50%, without any impact on safety. If buildings are also maintained for their full design life and not replaced early, the sector's emissions could in total be cut by around 80% - the target set in the UK's 2008 Climate Change Act.

New research from the ̽��ֱ�� of Cambridge has found that the amount of steel used by the construction industry, and the resulting carbon emissions, could be significantly lowered by optimising the design of new buildings in order to use less material.

At present, in order to keep labour costs down, the construction industry regularly uses double the material required by safety codes. Analysis of more than 10,000 structural steel beams in 23 buildings from across the UK found that on average, the beams were only carrying half the load they were designed for. ̽��ֱ��results are published in the June 4th issue of the journal Proceedings of the Royal Society A.

Over one-quarter of the steel produced each year is used in the construction of buildings. Demand for steel is increasing rapidly, especially in the developing world, and is expected to double in the coming decades.

̽��ֱ��iron and steel industry contributes nearly 10% of total global carbon emissions, which climate change experts recommend be halved by 2050. Coupled with skyrocketing demand from the developing world, drastic action is required if a reduction in the sector’s carbon footprint is to be achieved.

One option to achieve this reduction is by designing and building more efficiently, delivering the same performance from buildings but with less steel, but this is not common practice at present.

“Structural engineers do not usually design optimised structures because it would take too much time; instead they use repetition to decrease the cost of construction,” said Dr Julian Allwood of the Department of Engineering, who led the research, which was funded by the UK’s Engineering and Physical Science Research Council (EPSRC). “This leads to the specification of larger steel components than are required.”

̽��ֱ��researchers found that building designs are exceeding Eurocode Safety Standards by a factor of two and so are unnecessarily using double the amount of steel and concrete needed. “As materials are cheap and structural design time is expensive, it is currently cheaper to complete a design by using safe but considerably over-specified materials,” said Dr Allwood.

Additionally, many buildings are being designed to last for 100 years but on average are replaced after just 40.

By designing for minimum material rather than minimum cost, steel use in buildings could be drastically reduced, leading to an equivalent reduction in carbon emissions, at relatively low cost. ̽��ֱ��net result of avoiding over-design and early replacement is that the UK could provide the same amount of built space with just 20% of the materials - and therefore 20% of the carbon emissions - used at present.

“We need to see a more sensible use of materials in the construction sector if we are to meet carbon reduction targets, regardless of the energy mix used in manufacturing the materials,” said Dr Allwood, who is also Director of the UK INDEMAND Centre, which aims to enable delivery of significant reductions in the use of both energy and energy-intensive materials in the industries that supply the UK’s physical needs.

̽��ֱ��construction industry could slash its carbon emissions by as much as 50% by optimising the design of new buildings, which currently use double the amount of steel and concrete required by safety codes.

We need to see a more sensible use of materials in the construction sector if we are to meet carbon reduction targets

Julian Allwood

Andreas Levers via Flickr

Construction

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