Aggregation of Sustainable Gains

It’s a cold day.  You’re out for a walk, hands thrust deep in your pockets, protecting them against the bitter wind. On the path ahead of you something glittering catches your attention.  On closer inspection you see that it’s only a penny coin.  Do you pick it up and pocket it? More likely you’ll carry on walking, thinking you don’t know where that coin has been, it’s so cold you don’t want to take your hands out of your pockets and anyway, it’s virtually worthless, you can’t buy anything with it.

If it was a pound coin you might have picked it up.  If it wasn’t glinting but a rustling £20 note you almost certainly would have bent down and grabbed it and thought today was your lucky day.  In 2003, one man who did metaphorically pickup that 1p coin was Dave Brailsford and he used it to transform British cycling.  Since the start of the modern Olympics in 1908, Britain had won one solitary gold medal in cycling and our record was even worse in the most prestigious cycling race in the world, The Tour de France, which had never been won by a British cyclist in over 100 years of trying.

One penny is 1% of one pound.  Dave Brailsford the newly appointed coach of British Cycling and his team broke down everything you could think of that goes into riding a bike, and then set out to improve it by 1 percent.  Bike seats were redesigned, fabrics that were used for cycling jerseys were tested in wind tunnels even different massage oils were evaluated to see which gave the best performance. Within 5 years of starting this process that Brailsford called the “Aggregation of Marginal Gains”, the British team were dominating cycling.  In the 2008 Olympics the British team won 60% of the gold medals available, in London 2012 the did even better winning 16 gold medals across the Olympic and Paralympic Games, setting seven world records in the process.  The following year Bradley Wiggins won Britain’s first Tour de France and with Chris Froome and their Sky Team colleagues went on to dominate, winning 5 out of 6 Tours.

We are trying to harness this concept at work and apply it to sustainability of our projects.  Throughout the design process we will be looking for those small marginal gains (as well as big ones).  Whether it’s making a saving in the size of an element or reusing some existing foundations instead of building new ones, or increasing the slag content in concrete, or reducing the reinforcement by reviewing crack widths.  Imagine what a difference we could make if we can be as successful as the cyclists.  To help embed this practice in our work, we are developing a dashboard to help quantify and share some of these improvements.  Initiatives will be peer reviewed within the app and prizes will be awarded.

By aggregating our sustainable gains we may not win any gold medals, but our eyes are set on a bigger prize – net zero.  If we hit that target, we will all be winners.

Jackhammer not Jackboot needed

Okay, so I have a reputation of defending all things concrete, but sometimes you wish that the
material was not so durable and capable of withstanding the ravages of mother nature, instead like a sandcastle on a beach, it would be nice if it could get easily washed away.

A Croydon office being recycled

Clearly, you can recycle concrete and I’ve worked on a number of projects where we have looked to
turn old concrete structures or elements into crushed concrete aggregate (as it is called in BS 8500,
the UK British Standard for concrete). CCA can be reused in concrete as a replacement for natural aggregate. When concrete is part of general demolition waste and may be contaminated with other materials like bricks or plasterboard (the latter being a particular problem because excess gypsum disagrees with concrete) then its reuse is probably best left to low-tech applications like fill or hardcore.

However, having read of a recent landscaping scheme by a Mr Steven Johnson of El Sobrante, California, I cannot wait to see this particular use of concrete be subjected to a pneumatic drill and be smashed into oblivion or better still into CCA so that something positive can be crafted out of Mr Johnson’s monstrosity.

I am sure that like me, those of you that have seen or heard the coverage of the 75th anniversary of the D-Day landings in northern France will have found it moving and poignant. Yet, while we were marvelling at the tales of bravery of those once young men storming the Normandy beaches, Mr Johnson
decided that this was a good time to unveil a 3x3m concrete swastika in his front garden.

Mr Johnson’s garden “improvements”

Apparently, he thinks it looks “cool”; he likes swastikas and to him they symbolise “peace tranquillity and harmony”. Try telling that to those surviving veterans that saw their mates cut down in a hail of bullets.
Let’s hope that Mr Johnson soon sees sense and removes this offensive symbol. I’m sure he’ll find many volunteers to help him turn it into a pile of CCA. Now where did I leave my grading sieves……

Wood you believe it?

Oh dear, the New Scientist is the latest publication to fall under the spell of ‘timber can save the
world’ mantra by replacing the evil that is concrete (The New Age of Wood, 16th March 2019).

The article argues that we live in the “hydrocarbon age” which makes possible the materials that ‘define our
civilisation: steel, concrete and plastic’. It goes on to claim that “everything that is made from fossil-based materials today, can be made from a tree tomorrow’. While some examples are obvious, e.g. timber buildings, others require new technologies. Apparently, a timber ‘tougher and stronger’ than
high performance steel can be made from soft wood. Obviously, it must be processed first, which involves ‘chemically removing half of the lignin then brutally compressing what is left at high temperature’. No mention is made of how much carbon is emitted in this process. I wonder what
solution they will claim can replace concrete paving or asphalt roads. Perhaps they’ll transform
timber decking into something that can survive being run over by all the articulated lorries that will
be needed to haul all that imported timber and timber products around the country. Better hope it doesn’t rain, it might get a bit slippery!

I have rehearsed the arguments about the carbon content of concrete before and how it is a victim
of its own success and talked about the disadvantages of CLT, e.g. the poor acoustic qualities that required a school to ban pupils from talking in the corridors and the peeling layers that
means it can add fuel to a fire.

Let’s consider some of the other issues that get glossed over.
Where are you going to put all these trees? Has anybody worked out how many trees would need
to be planted to replace all concrete, steel and plastic and would there be any land left over to
provide food for the world’s growing population or house them?

Apparently, one cubic metre of timber stores one tonne of CO2, which contrasts positively to
cement where one tonne of cement creates getting on for one tonne of CO2. However, concrete is a
low carbon material because not much cement is used in its production (and that cement is often partly replaced by low CO2 products like slag and fly ash). What happens at the end of life? The timber will probably be burnt to produce energy also known as releasing all that stored CO2 back into the atmosphere. So, when the New Scientist claim “switching to timber would immediately wipe a billion tonnes off global carbon emissions”, what they fail to add is that in 50-100 years time much of it will still end up in the atmosphere. Concrete by contrast, reabsorbs CO2 throughout its life by a
process of carbonation. At the end of its life, if it is crushed up to produce recycled aggregate, the
increase in surface area of the particles will accelerate the carbonation, increasing the amount of
reabsorbed CO2.

Don’t get me wrong, I’m not saying don’t use timber, or develop new technologies. What I am
saying is that concrete is a wonderfully adaptable, durable, cheap and locally available product. Let’s
look at ways to improve further the sustainability of concrete, e.g. by sequestration of CO2, rather
than trying to create a concrete-free fantasy land.

What has limestone ever done for us?

It is strange that in an article condemning the so called “destructive impact of concrete”, the Guardian choses to illustrate it with the image of a limestone quarry rather than a cement factory or a concrete plant.

Is it because the modern production facilities do not present the negative image they are looking for?

Hope cement works

I mean apart from being a key ingredient in cement and the building blocks of many outstanding structures, why do we create this dust and scar the landscape?

According to the great (but not infallible) source, Wikipedia, limestone also has the following uses:

  • It is the raw material for the manufacture of quicklime (calcium oxide) and slaked lime (calcium hydroxide).
  • Pulverized limestone is used as a soil conditioner to neutralize acidic soils (agricultural lime).
  • It is the raw material for the manufacture of quicklime (calcium oxide) and slaked lime (calcium hydroxide).
  • Pulverized limestone is used as a soil conditioner to neutralize acidic soils (agricultural lime).
  • As a reagent in flue-gas desulfurization (it reacts with sulfur dioxide for air pollution control).
  • Glass making, in some circumstances, uses limestone.
  • It is added to toothpaste, paper, plastics, paint, tiles, and other materials as both white pigment and a cheap filler.
  • It can suppress methane explosions in underground coal mines.
  • Purified, it is added to bread and cereals as a source of calcium.
  • Calcium levels in livestock feed are supplemented with it
  • It can be used for remineralizing and increasing the alkalinity of purified water to prevent pipe corrosion and to restore essential nutrient levels.
  • Used in blast furnaces, limestone binds with silica and other impurities to remove them from the iron.
  • It is used in sculptures because of its suitability for carving.

I am sure you could come up with a lot more.

How do I sleep at night?

That was the question asked of me by a colleague, followed by a clicking sound as his tongue was extracted from his cheek, where it had been firmly planted. He had just read the Guardian article “Concrete – the most destructive material on earth”. The piece was a literary assault on the ubiquitous construction material written with such venom (even by the standard of that newspaper, which often has a very myopic view of the world) that had it been written about an individual rather than a defenceless material, libel lawyers around the land would be rubbing their hands in anticipation of the fat fees they would earn.

I must be a Carbon Criminal in the eyes of the Guardian, having spent my whole career working in different parts of the Concrete Industry. Concrete is blamed for everything from supporting corrupt governments to causing global warming or supporting organised crime. I have been toying with the idea of a blog on concrete for sometime and this article has been the catalyst I needed. It looks like the Guardian is going to have a sustained attack on concrete as they are promoting Guardian concrete week which will investigate the “shocking impact” the material has on the modern world”

It’s true that cement is an energy intensive material to produce and often bandied about is the statistic that each tonne of CEM I (aka ordinary Portland cement) generates one tonne of carbon dioxide during its production (the figure is actually less than that). But let’s not forget cement is not concrete; the two words often get mixed up and used incorrectly. The Guardian article falls into this trap when it talks about digging a hole and filling it with cement, but they are not alone.

Dan Brown got it wrong so many times in the Da Vinci Code sequel Angels and Demons that it spoilt the book for me. It was not a “huge cement bulwark thick enough to ward off attacks even by tanks”; it was concrete. And Ian MacMillan, who wrote in Neither Nowt Nor Summat, that his “Uncle Charlie and his son Little Charlie made sure they drew their initials in the cement when they built their new garage in the back garden of 34 North Street in 1963”. Uncle Charlie and his son little Charlie either wrote their initials in the concrete floor or the mortar between the bricks in the wall. They almost certainly didn’t write it in the cement (a fine grey powder that’s used to make concrete and mortar) and if they did it would have been blown away with the first gust of wind. This is simply WRONG and is equivalent to Mary Berry eulogizing about a delicate carrot flour with a scrumptious flavour on The Great British Bake Off? Flour is a powder used to make cakes; cement is a powder used to produce concrete.

The fact is that not very much cement is used in concrete, the rest of the materials (aggregate, water, admixtures and supplementary cementitious materials like ground granulated blastfurnace slag and fly ash) are typically extremely low carbon materials, so that a tonne of concrete of the type often used in foundations can have an embodied carbon dioxide content well below 100kg per tonne rather than 1000kg.

As the article points out, concrete is the second most widely consumed material in the world (after water). It can be aesthetically beautiful, it can be ugly. The fact is that without concrete our health and education would be poorer. In fact without concrete, we wouldn’t have the transport infrastructure allowing those papers to be distributed or the journalists to get to work, or the office blocks they work in, or the buildings to house the printing presses, or the shops to sell the papers in, or the electricity to run their laptops or, or, or…. (the list is endless) but in short, there would be no Guardian newspaper.

Coal, oil and gas produce more CO2 than concrete (but are used in much lower volumes), concrete has much lower CO2 content on a weight by weight basis than steel, asphalt and plasterboard. Concrete is a low carbon material and it is a victim of its own success. It is widely used because it is durable and cheap.

The article is light on suggested alternatives to concrete. Cross laminated timber is one suggestion. Obviously not suited for most of the applications that concrete is put to, it can be used for the walls of buildings. I am a governor of a school in west London, that despite my best efforts, was built in CLT. It looks attractive but there’s one big problem. The noise! CLT, unlike concrete, does not absorb noise and it was impossible to use the classrooms when there was any chatter in the corridors as pupils moved between classrooms. By necessity, the school had to implement a silence in the corridors policy.

Concrete also has inherent fire resistance unlike timber. The CLT industry has argued that you do not need to worry about fire in CLT buldings, because when they start to burn, the timber chars, effectively producing an inflammable surface on the CLT. While this may be true for solid timber, CLT is built up in layers and recent work has shown that the layers can peel providing additional fuel for the fire. In the post-Grenfell era, do we really want to promote timber housing with question marks over its safety?

Don’t get me wrong, I think the cement industry could still make giant leaps at improving the sustainability of its product. CO2 sequestration is one area to be more seriously addressed but the concrete industry is already doing a lot of good work. The UK concrete industry diverts over five million tonnes of material from external waste streams and uses them in place of primary materials. In 2014 it used 107 times more waste than it sent to landfill.

Despite the Guardian’s outpouring on concrete, to quote one of their other bête noire’s, the late Lady Thatcher,

“There is no alternative”