Saturday 26 January 2019

Concrete: a material of construction & destruction - and how to fix it

How often is it that we fail to consider what is under our noses? One of the most ubiquitous of man-made artifices - at least to the 55% of us who live in urban environments - is concrete. Our high-rise cities and power stations, farmyard siloes and hydroelectric dams wouldn't exist without it. As it is, global concrete consumption has quadrupled over the past quarter century, making it second only to water in terms of humanity's most-consumed substance. Unfortunately, it is also one of most environmentally-unfriendly materials on the planet.

Apart from what you might consider to be the aesthetic crimes of the bland, cookie-cutter approach to International Modernist architecture, there is a far greater issue due to the environmental degradation caused by the concrete manufacturing process. Cement is a key component of the material, but generates around 8% of all carbon dioxide emissions worldwide. As such, there needs to be a 20% reduction over the next ten years in order to fulfil the Paris Agreement - yet there is thought there may be a 25% increase in demand for concrete during this time span, particularly from the developing world. Although lower-carbon cements are being developed, concrete production causes other environmental issues as well. In particular, sand and gravel extraction is bad for the local ecology, including catastrophic damage to the sea bed.

So are there any alternatives? Since the 1990's, television series such as Grand Designs have presented British, New Zealand and Australian-based projects for (at times) extremely sustainable houses made from materials such as shipping containers, driftwood, straw bales, even shredded newspaper. However, these are mostly the unique dream builds of entrepreneurs, visionaries and let's face it, latter-day hippies. The techniques used might be suitable for domestic architecture, but they are impractical at a larger scale.

The US firm bioMASON studied coral in order to develop an alternative to conventional bricks, which generate large amounts of greenhouse gases during the firing process. They use a biomineralisation process, which basically consists of injecting microbes into nutrient-rich water containing sand and watching the rod-shaped bacteria grow into bricks over three to five days.  It's still comparatively early days for the technology, so meanwhile, what about applying the three environmental ‘Rs' of Reduce, Reuse and Recycle to conventional concrete design and manufacturing?

1 Reduce

3D printers are starting to be used in the construction industry to fabricate building and structural components, even small footbridges. Concrete extrusion designs require less material than is required by conventional timber moulds - not to mention removing the need for the timber itself. One common technique is to build up shapes such as walls from thin, stacked, layers. The technology is time-effective too: walls can be built up at a rate of several metres per hour, which may induce companies to make the initial outlay for the printing machinery.

As an example of the low cost, a 35 square metre demonstration house was built in Austin, Texas, last year at a cost of US$10,000 - and it only took 2 days to build. This year may see an entire housing project built in the Netherlands using 3D-printed concrete. Another technique has been pioneered at Exeter University in the UK, using graphene as an additive to reduce the amount of concrete required. This greatly increases both the water resistance and strength compared to the conventional material, thus halving the material requirement.

2 Reuse

Less than a third of the material from conventionally-built brick and timber structures can be reused after demolition. The post-war construction industry has continually reduced the quality of the building material it uses, especially in the residential sector; think of pre-fabricated roof trusses, made of new growth, comparatively unseasoned timber and held together by perforated connector plates. The intended lifespan of such structures could be as little as sixty years, with some integrated components such as roofing failing much sooner.

Compare this to Roman structures such as aqueducts and the Pantheon (the latter still being the world's largest unreinforced concrete dome) which are sound after two millennia, thanks to their volcanic ash-rich material and sophisticated engineering. Surely it makes sense to use concrete to construct long-lasting structures, rather than buildings that will not last as long as their architects? If the reuse of contemporary construction materials is minimal (about as far removed as you can get from the traditional approach of robbing out stone-based structures in their entirety) then longevity is the most logical alternative.

3 Recycle

It is becoming possible to both recycle other waste into concrete-based building materials and use concrete itself as a secure storage for greenhouse gases. A Canadian company called CarbonCure has developed a technique for permanently sequestering carbon dioxide in their concrete by converting it into a mineral during the manufacturing process, with the added benefits of increasing the strength of the material while reducing the amount of cement required.

As for recycling waste material as an ingredient, companies around the world have been developing light-weight concrete incorporating mixed plastic waste, the latter comprising anywhere from 10% to 60% of the volume, particularly with the addition of high density polyethylene.

For example New Zealand company Enviroplaz can use unsorted, unwashed plastic packaging to produce Plazrok, a polymer aggregate for creating a concrete which is up to 40% lighter than standard material. In addition, the same company has an alternative to metal and fibreglass panels in the form of Plaztuff, a fully recyclable, non-corroding material which is one-seventh the weight of steel. It has even been used to build boats as well as land-based items such as skips and playground furniture.

Therefore what might appear to be an intractable problem appears to have a variety of overlapping solutions that allow sustainable development in the building and civil engineering sector. It is somewhat unfortunate then that the conservative nature of these industries has until recently stalled progress in replacing a massive pollutant with much more environmentally sound alternatives. Clearly, green architecture doesn't have to be the sole prerogative of the driftwood dreamers; young entrepreneurs around the world are seizing the opportunity to create alternatives to the destructive effects of construction.

Friday 11 January 2019

Hot, cold or in between: thermoregulation and public misunderstanding of science

I recently spotted an intriguing paleontology article concerning the 180 million year old fossil remains of an ichthyosaur, a marine reptile from the Early Jurassic. The beastie, belonging to the genus Stenopterygius,  is so well preserved that it shows coloration patterns (if not the colours themselves) on patches of scaleless skin, as well as a thick layer of insulating fat or blubber. What makes the latter so intriguing is that reptiles just aren't meant to have blubber. Then again, like some snakes and skinks today, ichthyosaurs must have given birth to live young. Thus the gap between reptiles and mammals surely grows ever smaller?

This conundrum touches on some interesting issues about the public's knowledge of science. Several times I've commented on what Richard Dawkins calls the "tyranny of the discontinuous mind", which is the way in which we use categorisation to make it easier to understand the world. It might seem that this is the very essence of some aspects of science, as in New Zealand physicist Ernest Rutherford's famously ungenerous quote that "Physics is the only real science. The rest are just stamp collecting." Indeed, examination of the life and work of many early botanists for example might appear to verify this statement. However, there needs to be an understanding that science requires a flexibility of mind set, a fundamental scientific process being the discarding of a pet theory in favour of a more accurate one.

I'm sure I've remarked countless times - again, echoing Professor Dawkins - that science is in this respect the antithesis of most religions, which set key ideas into stone and refuse to accept any challenges towards them. In the case of the blubber-filled Stenopterygius, it is still a reptile, albeit one that had many of the attributes of mammals. As for the latter, from our pre-school picture books onwards we tend to think of the main mammalian subclass, the placentals, but there are two smaller subclasses: the marsupials, such as the kangaroo; and the monotremes, for example the duck-billed platypus. It has been known since the 1880s that the platypus lays eggs rather than giving birth to live young, a characteristic it shares with the other four monotreme species alive today. In addition, their body temperature is five degrees Celsius lower than that of placental mammals, part of a suite of features presumably retained from their mammal-like reptile ancestors.

Even so, these traits do not justify the comment made by host Stephen Fry in a 2005 episode of the BBC TV quiz show QI, when he claimed that marsupials are not mammals! Richard Dawkins has frequently pointed out that it would be unacceptable to have a similar level of ignorance about the arts as there is on scientific matters, with this being a clear case in point as regards the cultured and erudite Mr Fry. Yet somehow, much of the general public has either a lack or a confusion concerning basic science. Indeed, only  last week I listened to a BBC Radio topical comedy show in which none of the panel members could work out why one face of the moon is always hidden from our view. Imagine the response if it had been a basic lack of knowledge in the arts and literature, for example if an Oxbridge science graduate had claimed that Jane Austen had written Hamlet!

Coming back to the ichthyosaur, one thing we may have learnt as a child is that some animals are warm-blooded and others cold-blooded. This may be useful as a starting point but it is an overly-simplistic and largely outmoded evaluation of the relevant biology; the use of such binary categorisation is of little use after primary school age. In fact, there is series of steps from endothermic homeotherms (encompassing most mammals and birds) to ectothermic poikilotherms (most species of fish, reptiles, amphibians and invertebrates), with the former metabolic feature having evidently developed from the latter.

Ichthyosaurs are likely to have had one of the intermediate metabolisms, as may have been the case for some species of dinosaurs, possibly the smaller, feathered, carnivorous theropods. Likewise, some tuna and shark species are known to be able to produce heat internally, but in 2015 researchers at the US National Marine Fisheries Service announced that five species of the opah fish were found to be whole-body endotherms. Clearly, the boundaries between us supposedly higher mammals and everything else is far less secure than we had previously believed.

At times, science terminology might appear as too abstruse, too removed from the everyday and of little practical use outside of a pub quiz, but then does being able to critique Shakespeare or Charles Dickens help to reduce climate change or create a cure for cancer? Of course we should strive to be fully-rounded individuals, but for too long STEM has been side-lined or stereotyped as too difficult or irrelevant when compared with the humanities.

Lack of understanding of the subtleties and gradations (as opposed to clearly defined boundaries) in science make it easy for anti-science critics to generate public support. Ironically, this criticism tends to take one of two clearly opposing forms: firstly, that science is mostly useless - as epitomised by the Ig Nobel Prize; and alternatively, that it leads to dangerous inventions, as per the tabloid scare-mongering around genetically modified organisms (GMOs) or 'Frankenfoods' as they are caricatured.

Being able to discern nuanced arguments such as the current understanding of animal thermoregulation is a useful tool for all of us. Whether it is giving the public a chance to vote in scientifically-related referendums or just arming them so as to avoid quack medicine, STEM journalism needs to improve beyond the lazy complacency that has allowed such phrases as 'warm-blooded', 'living fossil', 'ice age' and 'zero gravity' to be repeatedly misused. Only then will science be seen as the useful, relevant and above all a much more approachable discipline than it is currently deemed to be.