Engineering and design student insights

Student projects, placements, research and study experiences in the Faculty of Engineering & Design

Tagged: dCarb

Live from the HIVE

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📥  Please categorise your post

Some days experimental research is just adding data points to a developing time series but other days mark a turning point. Today is such a day

Walls built;
Mortar cured;
Cavities closed;

Time to turn on the taps!

Well not straightaway;

First we had to install the temporary barrier and then harvested rainwater could be used to fill the tank. This took about an hour, during which the water crept up the outside of the stub walls, and snuck in to the cavities.

There was much scurrying of arthropods as beetles, moths and spiders vacated their nooks and crannies to flee the rising tide. Wildlife is one of the pleasures of the Hive - hares and buzzards are regular sightings - and the first webs had been built in the cavities before the stub walls were a day old.

Spider and Moth climbing walls to escape flood waters

Arthropods above the flood line

With 4 walls, using different combinations of brick and block, there was a chance to observe absorption patterns for the different materials. On the bricks, the mortar perps quickly darkened and fed an arc of moisture on the brick above.

Moisture line on cream bricks

The concrete blocks drew water up in a ragged line

Moisture line on blockwork

whilst the aircrete blocks were still bubbling up trapped air a couple of hours after immersion

Moisture line on aircrete blocks

The water will now stay in overnight, marinating the walls for 24 hours to tie in with smaller scale tests in the lab. And tomorrow the cell will be drained down and I will start to watch the walls dry...


A meeting of concrete geeks

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📥  Department of Architecture & Civil Engineering, Postgraduate

Who is a concrete geek: The concept of cement and concrete has been around for decades, one could even claim for millennia if Roman concrete is considered. Contrary to the common belief though, the long-standing presence of Portland cement in our lives isn’t analogous to our knowledge about it. Until the past century, when research started investigating cement’s intrinsic mechanisms, trial and error had been the only ways to manipulate its’ properties. Given its’ heterogeneous nature, there are still things to discover about the second most commonly used material in the world. All those then, who are fascinated by its potential and eager to unveil its secrets (including myself) are the ones to be called concrete geeks.


The meeting: This April I was given the opportunity to attend the “LC3 Doctoral School: Characterisation methods of blended cements” at École Polytechnique Fédérale de Lausanne - EPFL. It took place at the Laboratory of Construction Materials, Department of Materials of EPFL and it was organised by the team of Professor Karen Scrivener, Head of the laboratory and Editor in Chief of Cement and Concrete Research. From the 3rd until the 6th of April, approximately 30 participants from all over the word, from both the industry and academia, were brought together. Their common interest: cement and concrete science.

How I got there: I wouldn’t have been present at this event, had it not been for the two organisations that supported me. One was the Institute of Minerals, Materials and Mining (IOM3) with the Andrew Carnegie Research Fund and the second was the Armourers & Brasiers Gauntlet Trust with the Travel Grant for PhD Students for Conferences and Industrial Placements.

Content of event: The Doctoral School was an intensive training course about cement and concrete science, including lectures and practical sessions. The lectures covered a wide range of topics including both scientific aspects of cement and concrete science as well as geo-economic factors affecting its use worldwide.

A topic that received a lot of attention was the use of material characterisation techniques for cement and concrete. Techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) are commonly applied techniques for material characterisation. Although they are popular in a range of other fields, the intrinsic structure of cement makes it difficult to exploit their full potential. Therefore, appropriate application and interpretation is a burning issue in the research to obtain interpretable results. Other topics discussed were about common issues relating to concrete such as chemical shrinkage, creep, durability along with mitigation measures and principles of rheology and mix design.

The practical sessions took place at the facilities of the Department of Materials at EPFL. The sessions were hands-on and covered a range of techniques. More specifically, SEM and XRD for identification of cement hydration reaction products and calorimetry for investigation of reaction evolution. Also, methodologies for sample preparation for all these techniques, with special focus on samples for SEM, were demonstrated. During the practical sessions, the participants were given the opportunity to use the laboratory equipment and apply some of the demonstrated techniques themselves. Also, tours on the material preparation, concrete & structures and analysis laboratories took place. During those tours, the participants had the opportunity to discuss with PhD students, academic staff and technicians. This created an opportunity to explore areas of common interests and exchange research information. Finally, two events, a dinner and farewell lunch, provided additional opportunities for additional socialising amongst the organising team and the participants outside the course’s context.

My experience: The lecture “Cement and concrete in building worldwide” by Professor Karen Scrivener put in context how the earth mineralogy and geographic distribution of raw materials affect the use of cement and supplementary cementitious materials worldwide. Given the dispute about the environmental footprint of Portland cement, the availability of alternative supplementary materials is a burning issue in cement research.

The second session of lectures delivered by Professor Scrivener, “Cement hydration, kinetics of the reaction, aluminates & microstructure and final phases”, was an in-depth analysis of the hydration reaction of cement, the products and its kinetics. I found this lecture very beneficial and many of my questions were answered as I got a clearer understanding of the chemical processes I am investigating. Also, I had the opportunity to discuss some particularities of my own project and obtain valuable advice and material from the professor. Karen Scrivener is well renowned in the field of cement and concrete science for her research. Therefore, having the opportunity to discuss with her, opened new horizons for my work.

Two sessions that proved very beneficial for my project were the lectures “X-ray diffraction applied to cement” by Dr Ruben Snellings and “Porosity and microstructure characterisation” by Francois Avet. In the latter, the use of mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) for cement and concrete were discussed. Dr Snellings has been awarded the 2016 Gustavo Colonnetti Medal for his contribution to the field construction materials, while François Avet is now completing his PhD research in cement characterisation at EPFL. As mentioned above, the application of such techniques in the context of concrete is a matter needing attention. Given that the nature of the system I am investigating is much more complex than common concrete systems, I had the opportunity to discuss aspects of my project and get advice on how to manipulate the techniques to overcome the barriers I am facing.

The rest of the lectures, “Shrinkage and creep” by Julien Ston, “Concrete Durability” by Dr Hamed Maragheschi about deterioration reactions occurring in concrete elements (carbonation, chloride attack & alkali silica reaction) and “Rheology and Mix design” by Dr Aurelie Favier, were very enlightening. All the presenters were willing to share their knowledge, discuss aspects of my project relating to their field of expertise, provide advice and reading material or even establish communication with members of their team.

On top of the actual training, the opportunity to interaction with the rest of the participants helped broaden my view. The diversity of backgrounds, various places around the word and the mix of academics and professionals made the interaction very interesting and fruitful. We were given the opportunity to discuss about grounds of common interest, diversity of methodologies and approaches and of course exchange advice (as proper concrete geeks would do).

Outcome: Overall, I could conclude that I am very grateful to be given the opportunity to take part in the LC3 Doctoral School at EPFL. I had the opportunity to meet well renowned experts in my field, interact with people sharing the same interest and problems, get introduced to different perspectives and finally enrich my knowledge. The benefits are not to be counted only in terms of knowledge but also the opportunity to prepare the ground for future collaborations and develop as a researcher through the exchange of information with my peers.



The Destruction of Memory

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📥  Department of Architecture & Civil Engineering, Postgraduate

Why is architectural heritage targeted in war? And what can we do to protect it? Based on the book by architecture critic Robert Bevan, The Destruction of Memory reveals the destruction wrought by instances of cultural genocide across the world. Through exploring contemporary struggles, including the ongoing actions of Daesh (ISIS) in the Levant, this film shows you both the war against culture, and the battle to save it.

On the evening of Tuesday 2nd May, ACE Society hosted around 30 students and staff in the Level 2 Studios of 4 East South to watch the film of “The Destruction of Memory” and discuss what it meant to us, personally and professionally.

Rebuilding of Ferhadija Mosque, Banja Luka, Bosnia & Herzegovina. Image: Derek Wiesehahn. Copyright 2016 Vast Productions USA

Rebuilding of Ferhadija Mosque, Banja Luka, Bosnia & Herzegovina.
Image: Derek Wiesehahn.
Copyright 2016 Vast Productions USA

We were fortunate to be joined by some special guests – Tim Judah, a reporter for the Economist on and author of several books on Balkans history; Ammar Azzouz, a trained architect and Bath alumnus from Homs in Syria, currently working for Arup in London; Ivan Gololobov and David Clarke, who teach and research in Russian and German Studies respectively, from Bath’s POLIS department.

After we’d watched the film and had a timely drinks and snacks intermission, we shared our perspectives on the film. This ranged from the historical, political and aesthetic, including some moving anecdotes of personal experience.

The following discussion was broad and challenging. We shared personal experiences of living and visiting cities recently shaped by conflict, and sought to answer the larger questions too. Will future generations inevitably repeat the crimes of the past? Is international law equipped to deal with these crimes? What is the balance in urban reconstruction between commemoration and moving on? There were few simple answers to be had, but much was learned in how to understand these complex situations – both as professional designers, and as human individuals.

The documentary unfolds in the crit bays of 4 East South.

The documentary unfolds in the crit bays of 4 East South.

We would like to thank the Dept of Architecture & Civil Engineering and the Edge Arts Community for funding and supporting this event, as well as our special guests for their time. It was an educational and thoughtful evening – a reminder that being the best designers and engineers is as much about listening as it is about speaking.


Passive House For All

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📥  Department of Architecture & Civil Engineering, Please categorise your post

Passive House for all

The 2017 international Passive House conference was set against a backdrop of reducing carbon emissions in Europe and the need to divest from fossil fuels to meet both national and local targets. Energy efficiency is key to this and passive house standards for both new build and existing buildings were proposed as the benchmark for domestic and non-domestic dwellings

The conference theme was ‘passive house for all’, and ‘all’ had many strands and meanings, some of which were less apparent, but may in the end have the greatest impact on the passive house movement.

‘Passive house for all’ meant many climates, and examples were given from the very cold  to warm and humid climates. Each had their own the challenges, in cold climates PHPP is sensitive to very small changes to insulation and thermal bridges, in warm and humid countries delivering cooling and moisture extract are the priorities. The presentations showed that the passive house standard is applicable and achievable in all these situations and that solutions and products are developing to meet these challenges such as a theoretical MVHR unit that will extract heat and moisture from warm humid dwellings and use this heat to create hot water.

‘Passive house for all’ also means delivery at scale, moving from a niche market to district wide developments. The EU funded project Sinfonia supports Germany’s targets of reducing fossil fuel reliance. (interestingly Germany’s priority is to remove nuclear power from the grid before coal and gas). This can only be achieved though wide scale deep retrofit projects to existing dwellings. Deep retrofit was the only solution as undertaking moderate refurbishment risked ‘locking in’ less energy efficient components and interventions which may require further upgrading later, or worse not be improved upon for cost reasons.

Delivering at scale also means building bigger, and several examples of high rise multi-family dwellings were given, both new build and retrofit. Here the challenges are very different.

How do you test the air tightness of a whole building containing 352 new apartments when the plasterboard is being installed on the ground floors before the airtightness work has been completed on the upper floors? The answer was to create zones to test sections, this gave confidence to the air tightness strategy and allowed for modifications to be implemented through the build.

Building at scale will also impact on the choice of services, 352 MVHR units means 704 punctuations in the building envelope, so centralised systems make better sense for air tightness, and release precious floor area in individual apartments, which in cities like New York is critical. However, in existing buildings the layouts may mean that individual heating and ventilation systems may be needed, especially in buildings were there is mixed tenure, i.e. tenants and leaseholders. An example was given of in-wall MVHR units which are suitable for small homes and apartments.

In Austria where many apartment blocks have external render this could be used as an external air tight layer, which avoids complex detailing at intermediate floors. A new product which was yet to go into production was demonstrated, which could test the air tightness of external render before any insulation is added to ensure that it is sound and suitable for creating the air barrier.

The main positive from the conference was how much more widespread passive house is becoming and how a standard, that was designed for the German climate, is being adapted and developed so that is it applicable in a wide range of climates, countries and building types.

The negative, many of the buildings are still being developed as prototypes, with people learning on the job, many presenters said they would not do now, what they did in the examples they were giving. The challenge to try and overcome this so that knowledge and training includes practical solutions to common problems to prevent each building being a ‘first’.

'Passive House for all'  presents a challenge to the Passive House Institute who manage the standard and the brand. If ‘all’ means global adoption, it is likely that different countries may have different approaches. The US already talk in BTUs and R values rather than kWh and U values and China may create its own relevant standards. Worldwide adoption has many advantages, look at the PV industry where prices have fallen, access to cost effective components would remove many of the barriers to passive house, however maintaining quality is key and ensuring that the rigor which means that a certified passive house will deliver on its design intent, is maintained

image from

Image from


Drilling into polyurethane foam


📥  Department of Architecture & Civil Engineering, Postgraduate

Continuing my investigation into the properties of both low and high density polyurethane foams and their suitability for 3D printing, the drilling resistance of test specimens was measured. Interfaces are a crucial element in 3D printing and the aim of the drilling was to discover if there was a change in the density of cured foam at interfaces and moulded boundaries.

Two types of rectangular block specimens were used:

Cut-edged specimens with an interface: The liquid components were poured into a tray in two stages. Enough liquid was poured in to expand and occupy half of the tray volume and once fully cured, a second quantity of foam liquid was poured on top of the cured layer.
Moulded one-layered specimens: the two liquid components were mixed and poured into moulds to expand and cure. Enough liquid was poured in to fully occupy the volume, therefore no internal interfaces were present in these specimens.
Drilling resistance was measured using a Sint Technology Cordless Drilling Resistance Measurement System. The position of the drill bit was linked to a software program to continuously record the force required to advance the penetration of the moving bit through the foam. Specimens were placed into position and clamped as pictured.


The results showed that the material was higher in density at interfaces and moulded boundaries, with the difference being most pronounced in the low density, high expanding foam – up to approximately ten times as dense. Drilling into polyurethane foam was an interesting and entirely new experience, with the drill gliding effortlessly though low density foam and the high density foam putting up a little bit more of a struggle!


Everyday tales for country folk...


📥  Department of Architecture & Civil Engineering, Postgraduate


I have been a city dweller for most of my life but my early childhood was rural with a herd of Friesian cows as immediate neighbours and the woods closer than the village shops. With such a background, The Archers has always felt like catching up with old friends and it was a terrible shock when the village suffered a devastating flood in March 2015. Time was suspended, in Ambridge at least, as the events of a single night were dramatised over several episodes. After the waters subsided the causes and consequences of the flood continued to be explored, intensely at first then periodically, as the village recovered and reflected.

Individual and community stories can be a useful source of information for understanding flood events but need to be used with care to ensure that they do not compromise privacy, security or wellbeing. This makes a dramatised story, where the reactions and responses of fictional characters can be explored in detail, very useful as the basis for considering how resilience measures might be developed and deployed.

One aspect of the flood that has been revisited has been the involvement of a certain Rob Titchener. He had been implicated in blocking a culvert that contributed to the extent of the flooding; he had been reluctant to help with rescue then hailed a hero for his actions; and there was suspicion over his involvement in the fate of a dog, Scruff, as well as the later disappearance of a migrant worker, Stefan. These were woven in to the larger scenario of his coercive relationship with Helen Archer, which reached a shocking conclusion last year.

It was as this story played out, that I discovered Academic Archers - a forum where storylines were discussed not just for their entertainment value but by experts with an intellectual interest in the storylines. So when a call for papers to be presented at a second conference was made, just days after characters had been discussing the drying times of their properties near the River Am, I took a deep breath and submitted an abstract.

By fortuitous timing, the Flood Resilient House at BRE Watford was launched just a week before the conference. Speaking to assembled built environment and insurance professionals before opening the house, Emma Howard-Boyd, Chair of the Environment Agency, emphasised the need for personal responsibility and welcomed the project as an opportunity to demonstrate and test solutions.

BRE FR House

This provided some useful details and photographs to use in my talk alongside mapping from fan fiction.  The house also featured on BBC Countryfile the next day though I am not sure how many of the audience will have seen it as the first section (08:30-16:30) was during the Sunday evening episode of The Archers!

DSC_0127 (2)


The shed – a short essay on architecture and society

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📥  Department of Architecture & Civil Engineering, Postgraduate

Think the shed hasn't made its mark on architecture and society? Think again...


A large proportion of talk from us researchers is about the value of our research, why it’s cool and how it could help sort out a lot of the world’s big problems. And so we should talk in such a way. But once in a while, it’s refreshing and invigorating to divert our gaze from the lofty questions and terrible predicaments of our age – and seek something new in a familiar design.

In the spirit of one of my literary heroes, Alain de Botton, I shall take you through a short illustrated essay to restore the dignity of that architecturally misunderstood, true friend of humanity – the shed.

What contributions has the shed made to architecture and society? Bob Harvey [CC BY-SA 2.0 (], via Wikimedia Commons

What contributions has the shed made to architecture and society?
Bob Harvey [CC BY-SA 2.0 (], via Wikimedia Commons

The Oxford English Dictionary's definition of the shed is rather narrow, focussing on the domestic garden or tool-shed...

“A slight structure built for shelter or storage, or for use as a workshop, either attached as a lean-to a permanent building or separate; often with open front or sides.”

… so I shall expand my scope to include warehouses and their ilk, arguably siblings of the domestic shed. Are you ready? Let's begin...


Breeds contempt! The shed has an unfortunate association with either domestic or working drudgery, so it is prudent to remind ourselves that it has been revolutionary in human history. It has enabled us to store our harvests - it would be hard to overstate the influence of this in the development of civilisation. My personal favourite example of this ‘early revolutionary shed’ has to be the Egyptians’ Granary structure in the popular PC game, Age of Empires. I don’t know of its archaeological accuracy, but what a thing of beauty!

Granary of the Egyptian civilisation in the Stone Age, as portrayed in Age of Empires I. Courtesy of Microsoft Studios.

Granary of the Egyptian civilisation in the Stone Age, as portrayed in Age of Empires I. Courtesy of Microsoft Studios.

Our ability to store food in warehouses is still vitally important today. How easy it is to take all this once revolutionary technology for granted today.

Although less true for foodstuffs, much is made of the influence of the digital retail economy’s influence on the urban built environment - its erosion of high streets and town centres. But it’s false to suggest that the web has dispensed with the need for retail buildings altogether. The enormous warehouses belonging to retail giants such as Amazon, Tesco, and notoriously, Sports Direct, are now the physical link in the fiendish process of sourcing and despatching products to and from around the world. Whether you love, loathe or tolerate them, these corporate behemoths who facilitate much of our daily lives with their logistical feats are, at the end of the day, still dependent upon the humble shed.

The enormous Sports Direct HQ and warehouse in Shirebrook, Derbyshire, UK.

The enormous Sports Direct HQ and warehouse in Shirebrook, Derbyshire, UK. Ian Paterson [CC BY-SA 2.0 (], via Wikimedia Commons


Many domestic sheds across the land are witness to nothing more remarkable than lawnmowers, long-forgotten trampolines and perhaps the odd model railway set, yet the shed is the prime haven for the discoverer and inventor.

Is it the freedom from distraction, protection from mocking voices or simply convenience has made the domestic shed the place of so much human ingenuity? Whatever its x-factor is, it has been birthplace for a plethora of advances, as diverse as Marie Skłodowska Curie and Pierre Curie’s early experiments on new elements to Sir James Dyson’s invention of the bagless vacuum cleaner.

The inspirational and architectural potential of the shed as resurged in recent years - perhaps by people seeking something lacking in their homes.

Marie Skłodowska Curie and Pierre Curie doing some Nobel-Prize winning work in their shed.

Marie Skłodowska Curie and Pierre Curie doing some Nobel-Prize winning work in their shed.


Cobwebs and some slightly wonky pine slats are de rigeur for most domestic sheds, whilst numbingly vast sheets of corrugated sheet metal are the look of choice for their industrial brethren. But this has not always been the case, and still is not always so. I shall use counter-examples that I have encountered on my travels in Somerset.

The Tithe Barn in Bradford-on-Avon impresses firstly by scale - it stands 51 metres long and 9.5 metres wide. Venturing inside, it reveals its astonishing craftsmanship – a timber cruck roof, most of which has survived from the 14th century, supported by the buttressed walls of fine limestone. Perhaps such grandeur is unsurprising, as it was built to serve Shaftesbury Abbey in Dorset, at that time the richest nunnery in England. Although I’m glad to see the back of the feudal system it facilitated, surely there is no finer shed then this in the land?

The stunning cruck roof of the Tithe Barn in Bradford-on-Avon, Somerset, UK. Courtesy of English Heritage.

The stunning cruck roof of the Tithe Barn in Bradford-on-Avon, Somerset, UK. Courtesy of English Heritage.

In more recent history is the Bath branch of discount supermarket Lidl, built in 1966-67. Originally built as a factory for a manufacturer of office furniture, I have judiciously deemed it an honourary member of the shed family as it was built as a single interior space. What makes it special is only visible once inside – influenced by the style of Mies van der Rohe, it was the first building in Britain to make use of Mero space frame technology for its roof trusses. On a social level, it was architecturally notable for having no partitions between craftspeople and managers. Converted to a Lidl within the last 5 years, one can admire the spectacular geometry above your head whilst in an achingly long checkout queue.

The roof trusses of Lidl in Bath, using a Mero space frame. Courtesy of Phil Turton / Historic England.

The roof trusses of Lidl in Bath, using a Mero space frame. Courtesy of Phil Turton / Historic England.


This statement might seem cheesier than a budget Parmesan - but sheds are really a lot like us humans. Though often seemingly dull, they often have the capacity to dazzle, either in the appearance or the activities they facilitate. And even when they really do seem dull, they fulfil critical functions in our societies incredibly well. How we’d miss them if they were gone.


Lifelong Learning - sharing a love of Structures


📥  Department of Architecture & Civil Engineering, Postgraduate

Clifton Suspension Bridge from the Observatory platform

Every student is different but mature students have had more time than most to accumulate differences! In my case, I have returned to study having worked in practice, qualified as a Chartered Structural Engineer, had children and taught at a post-92 University. But in each stage of this traverse through my portfolio career, I have been grateful for the support and inspiration of the Institution of Structural Engineers. This has included, but by no means been limited to, technical talks offering a window on others' experience. It is perhaps easy to take these for granted with the luxury of a choice of research seminars and talks on campus almost every week, but for Engineers outside research-intensive Universities the talks provide a valuable connection and opportunity for professional development. However, as a parent, it can be difficult to attend meetings, even when they are local. Six pm starts are great for those able to go straight from work but are not so easy when the logistics of juggling after school and evening childcare means dashing home before hand!

So I was delighted to see that the Institution of Structural Engineers President’s Inaugural Address this year was to be made available on Livestream. It was still challenging to get the children rounded up and fed for 6pm so it was a few minutes after that I tuned in but without the embarrassment of clunking doors and finding the last remaining seat. And as a remote viewer, fire evacuation procedures were of limited relevance in any case! By the time 2017 President, Ian Firth, started speaking, I was happily settled and beginning to appreciate further benefits. As a shorter than average Engineer, I am used to seeing only part of presentation slides unless the lecture theatre has a particularly generous rake or I have managed to get right to the front. This time I could see every slide and hear every word. The talk itself was interesting and entertaining; well worth catching up with as a webinar if you missed it live.

But an unexpected benefit of an evening webinar was revealed later. I’ve previously tended to join lunchtime events, linking to ICE Yorkshire for Jenny Cooke’s "Lunch and Learn" talk on Communicating Climate Change (still available) and to the BRE for an update on Peter Bonfield’s Property Flood Resilience Action Plan. These took place whilst my children were at school but with an evening meeting they were at home. My son first walked through as pictures of buildings following natural disasters were on the screen. He quickly concluded that Structural Engineers were not yet rivalling Danger Mouse in keeping London safe and returned to the TV. However, about a quarter of an hour later he rejoined me, just as Ian Firth was talking about the need for bridges in poor developing societies. This really grabbed his attention, not just because the children were of a similar age but because he also relies on a bridge for his daily walk to and from school, across the River Frome in Bristol.

Boy crossing river on an old footbridge

Hapenny Bridge across the River Frome, Bristol

He continued to watch with me through to the end, though was rather dismissive of the Robot Bridge Building as he’d seen it all before on Dick & Dom’s Absolute Genius: Monster Builds! The next day on our walk to school, we were able to discuss the talk further and think about how he would improve the bridge. This led rather neatly into a weekend where we saw both Second Severn Crossing and the Clifton Suspension Bridge from unusual perspectives.

Second Severn Crossing from Spaniorum

A privileged view of the Second Severn Crossing

So thank you IStructE for allowing me the opportunity to see such an interesting talk - and thank you Ian Firth for inspiring not only me but a 10 year old who is already considering whether he might be able to follow Brunel beyond the Avon Gorge.

An edited version of this blog is available on the IStructE website




📥  Department of Architecture & Civil Engineering, Postgraduate

My PhD project, looking at materials suitable for 3D printing buildings using swarming aerial robots, began with investigating low density, expanding polyurethane foam ‘LD40’ (a) manufactured by the company Isothane. Now it is the turn of high density polyurethane foams, and the studies have used Reprocell 300 (b) and Reprocell 500 (c), commercially available foams manufactured by the same company.


While LD40 is established in the construction industry as an insulating material, the higher density foams are not readily associated with construction. Reprocell 300 is usually found as a substitute for timber in prop and set design along with applications such as balustrades and mantelpieces, whereas Reprocell 500 is primarily used for deep sea buoyancy applications.

Blocks of foam created so that the materials may be tested in line with the British standards, have been primarily made by hand mixing on the high density foams, such as the compressive strength test specimens shown in the figure.

Through trial and error, I arrived at a recipe for making the high density specimens. Firstly, I heat the two liquid components (one resin, one hardening agent) to 30°C, pour together and hand-mix for 90 seconds. The creamy, viscous liquid then turns a darker brown and becomes much less viscous as the mixed liquid heats up and the polymerisation process begins. I then stir again until the 150 second mark, at which point the material expands. A few more careful stirs then follow until I withdraw and the material quickly hardens, becoming solid at 180 seconds and feeling like a block of concrete.

This recipe has produced specimens which exceed the density stated in the manufacturer’s literature, most notably with the Reprocell 500 (specimens average 685 kg/m3). Compressive tests on the 500 have shown strength in excess of 30 MPa, astonishingly competitive with concrete. Flexural tests have also shown strengths indicating the material is competitive with the lower range of timbers. Reprocell 300 has around a third of the compressive strength of the 500.

Reprocell 500 has therefore shown that it has potential to be a structural material. The downside of denser specimens of course is that the material does not expand quite so freely so I am having to use more of the liquid components!

Making 500 specimens with my little syringe device outlined in the previous post has proved to be challenging. Despite experimenting with longer tubing and multiple static mixers, the material is being deposited in its creamy viscous state, and then the darker / hotter / thinner / runnier phase is occurring on the surface of the mat after deposition, leading to lateral spreading.

After the current round of tests are complete, several options will be investigated, most notably whether a catalyst may be applied to speed up the reaction time and the investigation of whether particles can be added to the material to favourably alter its rheological properties – these may include clay nanoparticles, graphene, carbon fibres, or ways to combine the lower density foam with the higher density foam.

Barrie Dams 19/01/2017