Sunday, March 29, 2015

Reused concrete - 6 points towards a rolling circular economy

The circular economy is recent years' sustainability buzzword. For concrete, it is an essential and ongoing search for better used of the raw materials (first generation) as well as the second generation materials.
[Image of the demolition of a large movie theater, Photo by Trondur Dalsgaard via]

Recycling seen from the heavy industry
Recycling and resource economy is not my speciality. So, leading up to my previous post about recycling concrete, I interviewed leading voices of the Danish concrete industry. Known to be as heavy an industry to move anywhere as their product when hardened, the opinion here is that business as usual is good. And reuse as excellent road-fill cannot be topped as the best - and only way to reuse the sky-high 95% of the concrete waste from infrastructure and buildings. It is nice to extend the life of the material yet it is unlikely to enter an extra cycle of use from here.

[Mixed concrete and asphalt waste. Image via

Since this is my private blog, however, there is room to have doubts about this single and and, let's admit it, single-minded opinion.

I have lately attended a number of recycling conferences. I have collected six points towards a better circular economy for concrete.

1. Know the source and the quality of your second generation material. This is the great challenge for all materials in construction. It is a matter of strength for construction materials, and to locate beautiful old windows treated with lead-based paint, railway sleepers with all sorts of nasty heavy metals, concrete with PCB, etc.

2. No extra cement to compensate. New concrete made from a mix of first and second generation concrete materials (gravel, sand, and larger aggregate) has been made and without using the extra cement to compensate for unknown qualities. - it is not a commercial practice.

3. New structures need not be constructed to last 100 years. The Danish industry produces high-quality concrete. Producing concrete of a slightly lower quality may be the consequence of using secondary materials - and this may be just fine.

4. Empirical tests
Concrete strength is always tested for any batch of mixed construction concrete - for reused concrete as well.
[Image of compression test of concrete cylinder via]
[Numerous cylinders are cast and tested for all construction projects. Image via]

5. National regulations need to change approach from 'construction waste' to  'construction resource' The national regulations for waste materials were developed as such, that is - looking at second generation materials as waste and not resources. This means that rules are too strict to work with in practice.

6. Show me the money
New national strategy for resource efficiency point at a more material conscious practice that should be simple 'and only cost a bit more' as a speaker from the secretary of the environment said during a presentation. This is obviously a major challenge - who should pick this extra expense? And why not make economic incentives to reuse more? If you can run a business, there is a market.

In the 1970s demolition companies would actually bid how much they would pay to enter their projects because buildings contained value that these 'material brokers' would disassemble and cash in on. - today it is the opposite. It is expensive for clients to demolish buildings. - When we see the change back, it will be a sign that the circular resource agenda is actually on its way, rolling.

Monday, October 27, 2014

Concrete after dark - is there an afterlife for concrete?

Thoughts about reusing concrete are on my mind since giving a brief talk on the subject at the recent trade fair in Copenhagen called Building Green. Not commercially related, it is the younger little sister to the gigantic EcoBuild in London, focusing on - well - sustainability and Construction.

Concrete after dark
This blog is mostly about the joy of creating and making concrete. So, little thought has gone to its afterlife; the life after it has ended its use in structures. I am a big fan of robust architecture allowing for transformation of the structures into another use. The afterlife I am talking about is not this noble one. Instead it has the pragmatic association with billions of tons of concrete waste that is created as we demolish buildings, infrastructure, etc.

Crushed concrete - under ground
In Denmark 95% of demolished concrete is actually reused, mostly as road material underneath new roads. While not the most sexy idea to the Concretely reader, crushed concrete is actually very efficient and a better product than gravel to be used to support roads. Furthermore, it saves new gravel from being sourced. But what about the concrete - is this sort of downcycling really the best use of the once more prominent concrete structures of homes and offices and bridges?

According to the Danish industry, yes, it is. I would be very interested to hear what happens to concrete in other countries.

Crushed concrete - above ground
Below is an architectural use of crushed concrete. It is a detail from the Hanil Visitor Center Guest House, which @bruteforceblog brought to my attention through my recent engagement with Twitter. The project should be familiar with fabric formers as it features fabric formed concrete elements as one of the facades. The gabions were new to me. The use of metal cages with rocks inside has remained popular for landscaping and retaining walls for more than a decade now - since, was it Herzog de Meuron (?) used it aesthetically in a project. I think the idea of the reused concrete could have a decorative effect. This reuse of concrete will have but no impact on the environmental agenda - simply because of the lack of volume. But all change in reusing ressources is worth a thougth, in my opinion.
[Crushed concrete used instead of rocks inside gabions at the Hanil Visitor Center Guest House in South Korea (2010). Photo by Yong Gwan Kim, via Archdaily. Thanks Mike Eliason for the tip]

Is concrete concrete?
Back to the question of concrete - an often cried idea is, why not use crushed concrete and use it for new concrete? it seemingly makes sense. Materials used again for the same purpose. What is not to like? Yet, the problem boils down to the misconception that 'concrete is concrete', a uniform and raw material. The issue with crushed concrete is that you really don't know which quality it is has and how long it can last. This means that more cement is needed for concrete made from old concrete. Since cement is the biggest CO2-sinner of concrete, let's not embrase ideas that demand even more use of it.

What's left inside?
[Image of recent 3d printed structure in China using construction waste and cement, appears to be reinforced with glass fiber weave. via the AN Blog]

Recent 3d-printed projects like the one depicted above, produce structures from a concrete-like (cement-based) material. The drawbacks remain the same - you need a lot of cement- and do not know what's inside the waste materials. Scary, because lots of chemicals old nasty and health and bio hazardous stuff may be part of the mix. The issue of chemicals and hazardous waste is a major challenge for the reuse of many types of construction materials, including concrete.

Concrete as LEGOs?
In Denmark we have developed a serious and very efficient use of prefabricated concrete for construction. It is really the exception to use concrete cast on site. For this reason, another misconception seem to stem from the nice conceptual relationship between concrete slabs and LEGOs. Both are building systems. The latter you can disassemble and reassemble over and over again. The former, not so much. One reason is the fact that we actually cast the concrete elements together so they will gain a better structural strength as the structure becomes more monolithic, so to speak. This, on the other hand, means that you will have to break the same structure when you 'deploy' the building causing to break the 'concrete LEGO'. 
Another point with reusing larger concrete elements is that you do not know of the condition, nor of how it is reinforced. Sigh - why not concrete LEGOs afterall??

From network to units
Below are a couple of examples that actually reuse concrete elements. Refitting concrete tubes as temporary dwellings or hotel rooms. Or at least - let's say it is reuse - it could also just be new elements. Scepticism apart, volume and density issues with these projects are similar to the 'concrete gabions' above. But perhaps fun to stay in for a single night.

[Images of Das Park Hotel (2006) by Austrian Andreas Strauss. In his project concrete tubes function as basic sleeping pods. Via ]

[A recent Chinese version of the tube concept proves how the concept is more curious than cool. Do you think the rubble like support is more than looks? Via]
[Tubo Hotel in Mexico (2010) by T3Arc- now stacking the tubes and adding glass for a far more elegant look - still curious for sure. Via ArchDaily]

So - are there no examples of use of concrete - overground - of any significant volume? Is concrete waste just waste - or really nice gravel? Eventually, examples are bound to come up- and probably not in an architectural blog-

"Distress will teach a naked woman how to knit" - is an awful translation of a Danish proverb "Nød lærer nøgen kvinde at spinde". It means that if you really, really need to, you'll figure out a solution or develop a skill - such as make yourself clothing if you're naked - in other words, innovation because you have to. That's how it will be with reusing materials. It's how it is already - with concrete for now it is just slower to really pick up, somehow.

Since waste is a reneweable ressource, so to speak, and the planet is running out of the raw materials and prices are going up, we will find ways to reuse materials. One approach to get more use out of waste is to be more clever in designs. In fact - designing for no waste is key, right?

Where are the great examples?
 As mentioned earlier, I - and my colleagues at the Danish Technological Institute am very curious to find other examples, big and small, of reusing concrete. They don't have to claim to save the world.

Clever ideas are enough for me for starters. The joy of making concrete stuff is not exclusive to pouring - not completely, anyway.

Friday, June 13, 2014

Concrete board games for the summer

[I want - this cool concrete chess game that comes in three shades of gray, via]

Oh, wow, it's been a long while. So without hesitation, let's start where I ended last - with a Concretely favorite, the Danish manufacturer Contec.

Below are images of a selection of beautiful board games cast in three different shades of gray (no pun intended) smooth high strength concrete.- all ready for the summer - and I guess you can even leave the boards outside if you feel like it.
[Play bacgammon on a concrete board, Image via the Contec-shop]

[Play chess with the concrete queen and king, image via the Contec-shop ]

[Nine Men's Morris - I completely forgot about this board game. It looks cool in concrete. Via the Contec-shop]

Wednesday, August 28, 2013

Is concrete sustainable?

In the book Concrete and Culture by British architectural historian Adrian Forty that I wrote more about here, his interest in labor as a material is used to frame the subject of culture around the use of concrete. With themes spanning from sustainability and nature to art, politics and economy, and time/weathering, Forty discusses concrete as a symbol of all, or the opposite. Despite its historical nature, I really appreciate the pages that Forty invests in the crucial discussion about sustainability – is concrete a sustainable material or is it not! Cons point at the high use of energy to produce cement. Cement is made from baking its raw materials, limestone and clay, at 1450 degrees Celsius – conservatively stated, 5 % of the world’s CO2 emissions come from the production of cement. – it is hard to be precise because it is uncertain how much cement is actually produced, between 1.5 and 2.5 billion tons. A rule of thumb from traditional production is that the production of one ton of cement emits one ton of Carbon. Around 50 per cent of the carbon emissions are the result of the chemical reaction; around 40 per cent by the burning of fuel in the kilns, and about 10 per cent come from fuel to extract and transport the raw materials.

Forty discusses ways to reduce either the use of fuels and the amount of cement used - the most effective way to decrease the carbon emissions is obviously to limit the use – while maintaining the properties and quality of the end product – most extremely is to leave the hydraulic Portland cement out and use pre-modern building technology in an industrialized way. An example is hemp-concrete – in which lime and vegetable aggregate mixed with organic hemp fibers as reinforcement for a lightweight non-structural product, with sound-absorbing properties.
[While hemp is naturally growing, one could then discuss whether crops should be grown to supply the World population before building blocks?]

Forty describes aspects of an important and more complex issue of energy use in building which means that one cannot rule out concrete as the biggest energy sinner. While concrete is heavy on carbon emissions during construction, figures from the British Concrete Centre estimate the ‘typical’ 60-year life of a building that about 10 per cent of its CO2 emissions are attributable to construction, and about 90 per cent to heating, cooling and lighting. 90 per cent. This indicates clearly the importance of focusing on the energy use and culture over buildings’ lifetime. Furthermore, heavy buildings (brick and concrete) heat and cool slowly due to the thermal mass. This means that these building types tend to overheat less than more lightweight structures – and will do so in the estimated steep rises of summertime temperatures.

I hate it when I feel like a used car sales person by pointing out benefits – my aim is to add some nuances to the good concrete vs bad concrete (non-)discussion. Judging by the quotes and the references Forty's section may have been written in 2009. This book will be read in ten and twenty years from now so accurate numbers is less important than and the multifaceted approach to the topic. The ten pages about the issue are obviously very general but highlight aspects of the topic of sustainability, of development and the politics and the blame pushed around in the world between the developed and developing countries.
The Concrete Centre uses a ‘typical’ age of 60 years for a building… what does that mean? – for sustainability’s (and everyone’s sake) build beautiful buildings. I heard partner Stephen Kieran of the architectural office Kieran Timberlake say something like this at a debate once: If architecture is ugly it will have a very short lifetime and will never be sustainable. Could this then, please, become a more prominent parameter in the various (expensive and thus complicated) certifications of buildings that pop up everywhere?

For more on the discussion about certifications and sustainability, do keep an eye and ear out for the talented architect and researcher Jan Schipull in his research and architectural work - as soon as he breaks the surface for fresh air after his PhD-dissertation-writing race. (The only decent link that includes some of his work is this presentation about Sustainable integrated product deliveries in renovation and new building construction)

The numbers in this post are all based on Adrian Forty's Concrete and Culture, a Material History, 2012

Concrete wilderness - Adrian Forty's Concrete and Culture - review

If not at the Concretely Blog then where? - I actually wanted to write a review on British architectural historian Adrian Forty's "Concrete and Culture, a Material History", published in 2012. But I haven't really finished,- so here is my recommendations to get the book as well as a few examples from the ten chapters framing dualities of concrete in regards to culture and architecture, the never changing paradox of concrete.
[Cover of Adrian Forty's Concrete and Culture. Via. Despite the beautiful picture on the cover, Forty has made a virtue of leaving out the money shots and this book is not a coffee table book - Forty has instead taken most of the photos himself and planned the research for the book to involve immense traveling to Japan, Brazil, Italy etc- oh the joy of being an architectural historian]

Anyone with an interest in concrete or in the discussion of how we understand and use concrete in architectural constructions should check out the book by British architectural historian and Professor at the Bartlett, Adrian Forty. I have been anticipating the publication of Adrian Forty’s book on concrete since I read his 2006 article ‘A Material Without a History’[1]. The article is much quoted for stating the somewhat obviously, that “concrete, let’s face it, is a process not a material.” Following this claim, Forty adds human labor as an ingredient in concrete – as well as cement, aggregate, reinforcement and water. Human labor is obviously an ingredient in other ‘natural’ materials too in order to make stones a cladding, or a tree trunk become a beam etc. For concrete, the work and process about concrete is just crucial and also links to the cultural side of the use of concrete, which is Forty's main objective.
"The book has turned out to be more about architects and architecture than I would have liked. Yet there is a good reason for this, in that architects have paid more attention to the interpretation of concrete as a medium." p11
The research on concrete as a medium (more than a material - which makes sense, I guess, because concrete is the lazy way of describing a group material technologies and practices with cement in common) started around the year 2000. Not an architect, Forty is attracted to the material “because of the inconsistency and contradictoriness of much that was said and written about it, and because of the absence of any coherent account of it as a major component of the modern world.” Forty says, “My work is not so much to increase detailed knowledge of the history of concrete, but rather to develop a general argument about concrete's role in the modern world, as well as within architecture.” [From the Bartlett profile on Forty accessed 26 oct, 2011]

[Lee Marvin as Walker in Point Blank. Via]
In the chapter on Concrete as Natural or Unnatural Forty discusses the changing views on concrete as a natural 'cultured stone' or a more unnatural, artificial building material. The continuous issue of weathering is discussed but also how concrete landscapes are used by film-makers. Though I have not seen John Boorman's 1967 Point Blank starring Lee Marvin, I especially enjoyed Forty's analysis of the use of empty concrete landscapes of Los Angeles taking the place of the classic and symbolic dessert as location. In scenes set against concrete, "men are tested, and sometimes destroyed." (p61)
[Image from the book of the reinforcement placed prior to the floor being poured in a villa by architect Rovelli. From the Hennebique archive. Image link via]

Concrete and photography is the topic of one of the interesting chapters of the book. The architect and scholar Guan Lee of the amazing Grymsdyke Farm was the first I have come across who used this comparison between the process as well as history of photography and concrete. His doctoral dissertation from the Bartlett has not yet been examined. Until then, the chapter written by Forty (also from the Bartlett, remember) offers one aspect of photography and concrete. The early pioneers such as Hennebique and Frank Gilbreth used the photographic medium commercially. Hennebique used photographs in advertisements to sell the systematic and well-proven methods using licensing. The photos had great compositions and were conveying the qualities of the product: its monolithic nature; the precision of the placement of reinforcement (which was invisible but essential features that the client could not see in the end product) – Frank Gilbreth used photography for management - quality control in order to document the construction process on remote construction sites.

Falling apart
One big shame and great nuisance is the fact that most pages have fallen out of the copy of the book I got out of the library. It is ironic that a book about a sturdy building material is not able to stay together. I hope the copy I have ordered for myself may be from another batch, that reprints will solve this major embarrassment of the printer’s. For now, I will have to tie a pretty bow around the library book for other poor readers to deal with as well as trying to make a virtue out of it when I get my own copy.

[1] in [Forty,A. (2006), 'A Material Without a History' in Cohen,J-L., Moeller,G.M. (ed.) Liquid Stone: New Architecture in Concrete, New York: Princeton Architectural Press, (ISBN: 1-56898-570-3), 34-45.] 2006

Monday, August 19, 2013

Ole Egholm - Concrete making and formwork tectonics - doctoral defense

More flexible formed formwork tectonics
The Cast Thicket project I just wrote about here reminds me of work by the Danish architect and doctoral student Ole Egholm who also explores the formwork tectonics of folded plastic sheets. Egholm  is defending his doctoral thesis on Friday September 13th 2013 in Aarhus. His project is related to my own doctoral work in the sense that it is about concrete, formwork tectonics, about flexible formwork, uses Gottfried Semper and other similar theories and key texts about tectonics, and it is investigated through making with the assistance of lots of great students, yet Ole has a digital starting point where as my own investigations were analog. Also important is his focus on building systems based on concrete elements, for example the vault shown below. 
[Youtube video of the assembly of the ReVault]
The use of concrete elements in Denmark could definitely use a lift and Ole's approach is great. His project has the title The Tectonic Potentials of Concrete and you can read an English summary of it here. The experiment shown below is from the ReVault workshop made in Aarhus as a collaboration between researchers and architecture students from Aarhus and from University of Technology, (UTS) in Sydney, Australia.
[Images from Re-vault, via. Elements are connected with zip ties. See more images here]

Ole and I have found similar sources of inspiration and this becomes clear when Ole Egholm writes about his conceptual universe that it 
"is based on research into established writings concerning tectonic thinking. The ideas of German Theorist Gottfried Semper are presented as a strategy for describing form as a result of materials and technical matter. Furthermore the idea of poetic construction is presented. Set forth by the English / American theorist Kenneth Frampton, the idea is that poetic construction is achievable though attention the properties of materials, structural logics and the craft of making. The thoughts of Marco Frascari which suggest a reading of details as a creator of meaning are introduced to be able to help establishing a progression in the case studies. Due to the narrow research focus on the making of concrete, an additional conceptual framework which emphasizes tectonics as a physical phenomenon is presented: The relationship between material, technique and form. Finally, a distinction was made between relationships surrounding mould making and the actual creation of geometric forms in concrete. The former was referred to as mould tectonics, the latter concrete tectonics." From Egholm's summary
This relation between formwork principles and the cured physical manifestation (concrete) is what I relate to as Stereogeneity - I think that Ole, as I am, is drawing on the definition of tectonics presented by Eduard Sekler. - well, I did write an entire post about Sekler, the tectonic, and the relationship between the mold and the molded here

Revault credits, participants
Eleven students from Aarhus School of Architecture (AAA) and UTS
Dave Pigram -architect, Senior lecturer - UTS
Ole Egholm Pedersen - architect, ph.d. candidate - AAA
Niels Martin Larsen - architect, ph.d. candidate - AAA
Stefan Rask Nors - architect, assistant professor - AAA
Ronni Lundoff Madsen - M.Sc. Architectural Engineering - Alectia
Jacob Christensen - M.Sc. Architectural Engineering - Vision+

Yo_cy's formwork tectonics

[Light and space inside the Cast Thicket by yo_cy, via]
Cast Thicket or filigree concrete
I have forgotten to repost this award winning project by yo_cy from Tex-Fab’s APPLIED: Research through Fabrication competition at the University of Texas at Arlington, which is posted on blog of the Architects' Newspaper A/N Blog. The project is familiar to some fabric-formed filigree-like projects with a major difference that it is facetted structure. Yet, despite being inspired by textile-like mats used for casting walls (which you can see way below), the formwork material is actually thin, lasercut plastic sheets. I enjoy the combination of digital fabrication and of combining the lasercut plastic sheets with the hydrostatic pressure from casting. 
“[With this project] we are reacting to the singular material tendency of digital fabrication and [we have shown that] we can use the computer to coordinate different methods of making a material, and simulate that on a smaller scale.” says Tracy, via
[Cast Thicket principle Via]
Cast Thicket is both a form of construction and a finished design product. To produce finished forms of reinforced concrete, construction begins with the design of prefabricated steel struts, which are positioned using a system of interlocking laser-cut plates. Formwork is also prefabricated and attached to the joints. Plastic formwork is then detached and reattached as the structure grows upwards. The final product has the possibility for infinite variation. via the competition site 
[Cast Thicket by yo_cy]
The structure is awesome and perhaps also thicket like (the title contains a new English word for me) - it rather reminds me of columns in Gaudi's Sagrada Familia as well as art pieces by the wonderful Ernesto Neto who fills spatial fabric structures with everything but concrete and plaster. Instead he uses eps, sand, and even spices.
[Ernesto Neto's fabric-formed soft world]

[Each piece of the plastic casing is connecting by a series of tabs. Photo:Kenneth Tracy]
[The plastic mold is held together with plastic zip ties. Photo:Kenneth Tracy]

While I find the work of yo_cy wonderful, I still have to let out a big sigh because of the overly time consuming construction. The idea of the 'tailor-made' as something related to flexible formwork is still so heavily labor intensive as you can tell on the image above, and thus far from being scaleable. I guess the work now can be compared to crocheting and not sewing.

Woven formwork for Kopo House
I am not sure if this house has been built but I'd love to see it if it does - the project is in Indonesia and contains the literal exploration of manufacturing a formwork textile, I mean the textile is in itself a structure with its own principles and the larger the fibers, the is it a building component and material in itself. yo_cy's Christine Yogiaman and Kenneth Tracy state as their profile that combining labor intensive acts in craft culture with rule-based, digital frameworks their projects in Indonesia multiply the everyday to intensify space. The images on the project show initial weaving samples inspired by Ketupat a sort of rise casting formwork... (!) that are manipulated and given form before it is used as formwork for plaster, I think. Other images show larger scale casts of modules and some rebar, so something is definitely being built. Fingers crossed.

The formwork principle is inspired by Indonesian cast rice dumplings known as Ketupat - wow, see below how great they are!
[Ketupat - --- I love these throwaway sturdy lunch boxes]

[woven mats used as formwork and a plaster cast for the  Kopo House project. I'd love to see the full scale version of this! via - Wait - below are bigger prototypes investigating some formwork types]
[Images of the Kopo House investigations, by Yo_cy]

Credits of the Cast Thicket:  Fabricators TOPOCAST
Competition Tex-Fab’s APPLIED: Research through Fabrication competition at the University of Texas at Arlington 
Designers Kenneth Tracy, Christine Yogiaman
Location Arlington, Texas
Date of Completion February 2013
Material limestone powder, white fiber reinforcement, Poraver glass beads, metakaolin, superplasticizer, .03-inch plastic
Process Rhino, Kangaroo, Grasshopper