Green Building Forum - Sustainable Concrete Construction

Sustainable Concrete Construction

GBP-Keith — Tue, 01 May 2007 19:48:04 +0100

Posted by Keith but not necessarily endorsed by he!

According to the Concrete Centre, Concrete construction can combat the effects of global warming by lowering energy consumption and therefore carbon emissions, thus minimizing the need for future air-conditioning.

If you want to learn more about this, The Concrete Centre, is running an evening seminar on 21st June 2007, at the Queen Mary University College, Clerwood Terrace, Edinburgh EH12 8TS starting at 18:30.

The seminar will outline the principles of passive solar design and how thermal mass can reduce CO2 emissions during the lifetime of a building. It will also look at how other designers have addressed the problems and provided innovative new solutions, as well as discussing the sustainable credentials of using concrete, the material science behind it and the various facts which support its sustainable credentials for manufacture and specification.

The seminar is free to attend.

For further information and registration visit: http://www.concretecentre.com/events

Sustainable Concrete Construction

Guest — Tue, 01 May 2007 20:07:29 +0100

The best quality concrete bridges and structures etc suffer from carbonation (penetration of atmospheric carbon) No concrete exposed to air is immune to this. It gives todays concrete a life of about 40-50 years before maintenance required to exposed rusting reinforcing bar.
More atmospheric carbon - shorter concrete life!!

Sustainable Concrete Construction

fostertom — Tue, 01 May 2007 20:32:35 +0100

Posted By: Guestcarbonation (penetration of atmospheric carbon) No concrete exposed to air is immune to this. It gives todays concrete a life of about 40-50 years before maintenance required

What about ASMET? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=174&page=1

Posted By: (GBP) Keithhow thermal mass can reduce CO2 emissions during the lifetime of a building

I plead guilty to saying that thermal mass is Good generally - which is what the Concrete boys seem to be saying. Not so, I now realise.
Thermal mass can be great - but its thickness/density/conductivity have to carefully controlled so as to re-deliver the absorbed heat when it's needed, not when it's not.
At one extreme, a skin of blockwork or a concrete-plank floor may help to smooth out sudden temperature rises e.g. when the sun blazes in, but it won't store that heat for re-delivery for more than an hour or two.
At the other extreme, a very thick/heavy south wall may release into the interior its previous day's solar input just as the next day's sun comes up - bad timing!
Somewhere in between, a calculated mass can absorb heat all day and start re-delivering in a useful way sometime early evening, just when it's needed. Then, likewise the same mass can absorb night-time 'coolth' and start delivering it mid-morning, to counter the new day's solar gain.
So, it's correct that massiveness can be very important and beneficial, but only if understood and calculated. It can then function as a fair alternative to high U-value, amongst other things. I need to find time to study this - it's a big hole in my knowledge, and the building industry's generally. Who better than the Concrete Centre to make this info easily available? That's what they should be doing.
Mind you, if I were creating thermal mass, I'd look for any other way than concrete, to achieve that!

Sustainable Concrete Construction

Guest — Tue, 01 May 2007 20:40:57 +0100

Understanding and controlling thermal mass - water!

Sustainable Concrete Construction

Guest — Tue, 01 May 2007 20:51:51 +0100

There was a time when electric storage heaters were made popular by heavy advertising. People soon discovered that they were uncontrollable and they more or less disappeared. At the moment the same seems to apply to underfloor heating using a concrete slab to iron out the heating swings, however this too has the problem of slow response, especially on cold days when the sun comes out. As I see it, heating needs to have a swift response time, both up and down. A system that puts out heat at the wrong time is surely unacceptable.

Sustainable Concrete Construction

Guest — Tue, 01 May 2007 21:06:00 +0100

Tom,

What happened to Steveleigh?

According to the test reports from Portsmouth University on the roofkrete website the depth of carbonation penetration for roofkrete material (asmet material) is 0.2mm in 50 years.

If a motorway bridge was this good it would have a life of about five thousand years before the carbon hits the reinforcing bar!

Sustainable Concrete Construction

fostertom — Tue, 01 May 2007 21:09:14 +0100

Proper understanding and proper use of storage heaters, underfloor heating, slow/fast response etc, even skirting heating (pure convective - bad idea!) will follow from the 'lost' knowledge that I'm talking about.

Sustainable Concrete Construction

Jeff Norton (NZ) — Tue, 01 May 2007 22:57:20 +0100

Thermal mass is an interesting subject, the more I learn the less I seem to know! I design with it quite conservatively and mainly as a base heat (target 18 degC) with capacity to absorb more, then use specific heat sources for specific activities like in bathrooms to top up.
Concrete has it's positives and as long as it's energy return on energy invested is good then I see as a useful material.
There are some structures built in 1870's of concrete here in NZ (thats very old for here).

Sustainable Concrete Construction

paul johannsen — Wed, 02 May 2007 14:22:56 +0100

Concrete is great but there are so many versions of it. many of the roman buildings still standing are a testonomy to it but projects that use excessive volumes are simply missing the point.
Particular concern is that it requires an enormous amount of heat to produce it the first place (lime kilns etc etc). To reclaim it also requires another good helping of energy to break it up
Please specify and use the best product with the lowest embedded energy (some of the manufacturers are already providing this information if not ask).
Even greener are the earthcretes (using on site or local aggregates). The japanese are probably the world leaders in this technology using a wide range of alluvial and other "muds" to build their houses.

My opinion is that rather than use the generic term thermal mass we should concentrate on where and how the materials which can absorb heat can create comfort.
ie it is not meant to be put every where.
in the good ole days thermal mass was associated with chimney breasts and the north facing elevations ie those that both recieved heat and those that didn't.
agree with other contributors there is rarely one solution most successful projects use an integrated mix.

regards

PS does anyone know the actual recipe for waterproof concrete

Sustainable Concrete Construction

Guest — Wed, 02 May 2007 19:11:33 +0100

Paul Johannsen has a point.
But, should the concrete industry try to regain market share when.
US scientists believe that 10% of man made greenhouse gas is created when making concrete? It has been the most popular form of building material for years, however, the UK industry is loosing out to more friendly materials

Sustainable Concrete Construction

fostertom — Thu, 03 May 2007 01:52:19 +0100

Cement manufacturing produces more CO2 than the entire aviation industry - plane manufacture plus flying - and is increasing almost as fast.

Sustainable Concrete Construction

Guest — Tue, 08 May 2007 17:01:52 +0100

Some interseting discussions....

What people should be asking is where would we be without concrete? To comment on a few points...

In 2002, global cement production was responsible for around 3.63% of man-made CO2 emissions, not 10% as the one reader suggests (source: United Nation Environment Programme).
In 2004, the UK (and Crown dependencies) cement industry produced 1.74% of UK CO2 emissions (source: data from the British Cement Association and National Green House Gas Inventory).

In the UK, 2 tonnes of concrete are used per head of population per year - why - because it is a versatile, flexible, durable, inorganic, long lasting construction products that we could not function without in our modern world!

Proof of the excellent natural durability of concrete comes in the shape of Marine Crescent in Folkestone, an early concrete building that has stood just metres from the sea since 1870 and which, following renovation, looks set to celebrate its 200th anniversary with ease. Fourteen original dwellings converted into 91 contemporary styled apartments, fitting comfortably within the ODPM's minimum target for housing density. Acoustic and thermal values that conform with new Part E and L regulations respectively. And, above all, the re-conditioning and re-use of an existing building that has required comparatively minor remedial work, despite the harsh marine environment in which it is situated.

In spring 2004, the structural engineer's report on the by-then empty and largely derelict structure indicated that all the walls from a thickness of 150mm up to 450mm (the latter found in the basement) were in a satisfactory condition. Only some minor internal walls of 100mm thickness had in the end to be replaced.

The foundations, built straight onto the shingle, had shown very little movement over the course of 130 years, and despite the fact that the building had no design movement joints, it was felt that the structure's general robustness meant that none needed to be added.

Sea-facing balconies at first floor level had been made of concrete containing brick fragments, gravel and fine aggregate plus some small diameter steel bar reinforcement. These were found to be largely in good condition, although corrosion caused by wrought iron balustrades meant that some spalling had taken place towards their edge.

But the starkest contrast between different building materials emerged when it came to the condition of the bay windows. Bomb damage during the war destroyed the eastern-most section of the Crescent and it had been built again in solid brick. After 60 years, all the brick bay windows were found to have failed and needed to be completely rebuilt in concrete with a galvanised steel post and frame around the windows.

So what's it going to be like to live in one of the 1 or 2-bed apartments? Quiet for one thing, despite the relatively high density of the conversion. Acoustic tests performed by the contractors showed a performance of 57dB for airborne sound between partition walls, attained naturally by the mass of the concrete's construction. Lower energy bills should also be achieved by virtue of the same reason. The Victorian concrete's thermal capacity will keep the apartments cool in summer and warm in winter, with the highest energy efficiency to be seen in the semi-basements. The conversion of the basements into one-bed apartments ticks off another current sustainability requirement for optimum land-use a further advantage that concrete basement construction offers.

On visiting the Concrete Centres website they have some excellent infomation on thermal mass and climate change adaptation which is well worth a look - I am sure that the Olympic Delivery Authority were well advised by the Building Research Establishment (BRE) when they stated in their plans to minimise carbon emissions - "...The thermal mass and structure of the building will be utilised to minimise heating, cooling and electrical demand..."

Sustainable Concrete Construction

Guest — Tue, 08 May 2007 18:00:41 +0100

Guest
Thanks for explaining and correcting cement emission and useage figures but one good concrete building is not a proper representation of a successful building system or product. I would suggest one thousand good examples over a period of at least ten years to be a sound representation of a proven a track record.

Sustainable Concrete Construction

biffvernon — Tue, 08 May 2007 19:35:31 +0100

Posted By: paul johannsenConcrete is great

Some folk say Allah is great. Doesn't convince me.

(concrete hating atheist)

Sustainable Concrete Construction

dennis — Wed, 09 May 2007 09:03:10 +0100

Following on from what was said about the embodied impacts of concrete, if you put fly ash or GGBS in your concrete then you can reduce the embodied CO2 by 50% or even more. Not only does this reduce the carbon footprint it also utilises wastes from other industries in the manufacturing process, reducing natural resource consumption and avoiding landfill.

I have been researching embodied impacts of construction materials as part of my doctorate for the past 4 years. One of the most interesting things about concrete is that it normally travels less than 15 miles to site, compared to thousands of miles with the other major construction materials (such as timber and steel). Whilst not being sold on the Concrete Centre's argument when I first started my thesis, there is a lot in what they are saying. One only has to look at the landmark 'sustainability' projects to see that they have achieved their low carbon footprints by utilising the properties of concrete:
Hockerton Housing Project
BedZED
Wessex Water
Brighton Library
BRE's 'Environmental' Building
Thames Water
University of East Anglia
Barclaycard
The Scottish Office
Toyota GB
ING Bank Netherlands (as featured in "Factor 4")
Powergen

I could go on...

It is these inspirational developments that have been built over the last 20 years that have convinced me of concrete's credentials as a material for passive low carbon development. Once one adds up the benefits of operational carbon savings, and the occupational benefits that can be achieved using passive design (such as increased well-being and productivity, as the ING example in Factor 4 demonstrates), these outweigh any embodied impact negatives.

Sustainable Concrete Construction

Guest — Wed, 09 May 2007 14:01:57 +0100

Dennis
What about concrete carbonation and moisture penitration?

Sustainable Concrete Construction

biffvernon — Wed, 09 May 2007 16:53:36 +0100

>concrete ...normally travels less than 15 miles to site

You mean concrete, as in cement + aggregate + water. OK, and often only a wheelbarrow trundle away. But the dry cement travels a lot further. Or I've not noticed a cement works in avery village in the land.

Fly ash is obviously a good idea, not so far off the volcanic ash or pozzolan that the Romans used, but hang on, where's this fly ash coming from? Oh, a coal fired powerstation. Now we'd be shutting them down if we took global warming seriously.

Sustainable Concrete Construction

Kieran — Wed, 09 May 2007 18:01:50 +0100

Posted By: biffvernon>Fly ash is obviously a good idea, but hang on, where's this fly ash coming from? Oh, a coal fired powerstation. Now we'd be shutting them down if we took global warming seriously.

wel... come on, you can't have it both ways. Fly ash is a great example of recycling waste product and it doesn't just come from coal fired powerstations but as waste from other industrial processes. I'd like to know more about fly ash substitution. I have read that you can replace up to 60% of the cement content, does anyone have any more information on how to do this or suppliers who will provide a specfied mix? Is it widely done?

Sustainable Concrete Construction

Guest — Wed, 09 May 2007 20:40:49 +0100

Kieran,

Most of the big suppliers use PFA or blast furnace slag (a by-product of the iron industry) substitutes in their concrete production, cost being one of the main reasons - try http://www.greenspec.co.uk/html/materials/cementsub.html for more details.

Sustainable Concrete Construction

biffvernon — Wed, 09 May 2007 20:50:28 +0100

Ah, the iron industry. Now that's another one with a size thirteen carbon footprint. Who needs steel lintels anyway? If we want green and sustainable buildings we're going to have to use green and sustainable materials. Don't confuse not-quite-so-evil building with sustainable building.

Sustainable Concrete Construction

dennis — Fri, 11 May 2007 15:31:57 +0100

Biff,

When you say "green and sustainable materials" which ones are you thinking of?

Dennis

Sustainable Concrete Construction

alexc — Fri, 11 May 2007 22:13:41 +0100

Hi dennis. Kieran....
My knowledge of fly ash or GGBS in concrete is 15 years out of date, but those materials have their own properties which in the end mean more cement. It is cement in concrete that is the carbon wasting factor, you could make make concrete from lime mortar if you waited and eyed up your thickenesses.
Plus fly ash or GGBS may add unforseen contaniments, which are bad.

cheers

alex

Sustainable Concrete Construction

alexc — Fri, 11 May 2007 22:36:00 +0100

I take most of my former comments back. I have obviously forgotton too much(reading the link u gave). Though i note that it is the most beneficial type(F) that is least likely to be used due to the slow setting properties.

Sustainable Concrete Construction

Geoff Beacon — Fri, 11 May 2007 23:46:12 +0100

In memory of Herman Kahn
See: http://en.wikipedia.org/wiki/Herman_Kahn

CONCRETING THE UNTHINKABLE

Climate change is worse than even the "expert" climate
modellers are predicting. We will soon discover
this to be true. That is my prediction.

So we must begin carbon sequestration and live in a
way that stores carbon rather than emits it --- and
in a big way. We must show the rest of the world how
this might be done, design lifestyles that they can
buy into. If we can't we might need to consider
military force.

First, getting our own house in order is imperative.
And talking of houses we must build them to store large
amounts of carbon, which has been extracted from the
atmosphere. It doesn't matter if this is short-term
(decades), without action there is no bearable
medium-term, let alone long term.

So let's set a target of building 70 tonnes of CO2e
into any dwelling during construction - rather than
emitting 70 tonnes during construction. That means
almost no products that have high embodied CO2
can be used. That means little or no concrete amongst
many other products. And, if that did mean no
structural elements capable of supporting buildings
much above the ground floor then so be it. We must
live on the ground floor.

We must also use non-fossil fuel energy (e.g. off-shore
renewable energy) so the heat storage ability of
concrete becomes irrelevant. Anyway, this is not
necessary if we believe the Hemp and Lime people.

I went to the Centre of Alternative Technology
recently for a "Hemp and Lime" conference. Several
of the speakers discussed the CO2 impact of Hemp
and Lime: basically it stores CO2 taken in during
its growth. One speaker estimated that 30 to 50
tonnes of CO2 can be sequestered in an average
house.

Of course there are many other things we must do
- or rather not do. Not fly, not drive etc.

But back to the military option: Say we were
concerned about forest destruction in the
Amazon basin. We would threaten to nuke a city
in Brazil, but to be equitable, (because we
have carbon-sinned more than they have) let
them nuke a city of ours with twice the population.
Before this we should, of course, offer the
Brazilians lots of money to be ecologically friendly.
And the Chinese ...

Herman Kahn would have insisted we must be
prepared to go ahead with military action if
we make the threat. But I remember James
Lovelock, who is an advocate of nuclear power,
recently saying that a nuclear war would not
kill as many as the coming climate change
catastrophe.

I will probably regret this tirade when I'm sober
and may wish I had not used my real name. But
I have friends who know about these sort of
things and they tell me that there really are
policy analysts paid to think these thoughts.

GIZZA JOB!!

Sustainable Concrete Construction

biffvernon — Sat, 12 May 2007 11:59:55 +0100

Posted By: dennisBiff,

When you say "green and sustainable materials" which ones are you thinking of?

Dennis

See the first half of the poem 'Concreting the Unthinkable' by Geoff Beacon, above.
( I presume, from the pattern of formatting, that it is poetry, though the rhyme and rythm are somewhat lacking.)

Sustainable Concrete Construction

Geoff Beacon — Sat, 12 May 2007 17:59:23 +0100

Thanks Biff

It wasn't poetry. My poetry has more rhythm (not too much) and more
rhyme (not too much). The lines were a bit short but most lines on
discussion forums are too long ... I think newspapers have it about
right for readability.

But if you want some of my poetry:

ONE PERFORMANCE ONLY

We'll fly you over burning forests
We'll walk you through the starving hordes
We'll shoe you drowned and bloated corpses
At a price you can afford

You'll fly above the sky in comfort
You'll sleep your nights in quiet hotels
You'll sit and watch our views in comfort
Of mankind in a thousand hells.

(Correction: for thousand read billion)

Also see http://auntiejaynesolvesyourpoem.com

Sustainable Concrete Construction

paul.dixon27 — Sat, 19 May 2007 09:05:32 +0100

both concrete (OPC) and lime re-absorb the co2 that they give off during manufacture. The fuel used to heat it and the quarrying and grinding up are significant but the co2 given off by the limestone is largely re-absorbed.I don't really understand this differentiation, that lime is an environmentally friendly material and concrete isn't. Both are made from limestone heated to the same sort of temperature, the main difference is that concrete has clay added to it.
I can only think that it's an aesthetic response to the material that gets confused with, or transmutes into, a belief that it objectively has a worse carbon footprint.

Sustainable Concrete Construction

biffvernon — Sat, 19 May 2007 10:10:15 +0100

Posted By: paul.dixon27both concrete (OPC) and lime re-absorb the co2 that they give off during manufacture.

No. That just ain't true. The reaction calcium carbonate to cacium oxide to cacium hydroxide and back to cacium carbonate is exactly cabondioxide neatral (ignoring fuel used). The maunfacture and setting of OPC is much more complex but is not CO2 neutral. More is evolved that re-absorbed on setting.
And lime making uses less fuel than OPC making, mostly because temperatures are lower.

Sustainable Concrete Construction

John Daglish — Mon, 21 May 2007 17:43:16 +0100

An interesting alternative production technique for artificial portland cement / OPC which can use up to 50% less cement for the same performance characteristics is EMC Cement (energetically modified cement). It is a simple patented technique developed in Scandanavia that intergrinds cement with an aggregate ( sand or slag, etc) such that the surface area for chemical reaction is significantly increased. A company in the US is now producing it under license see http://www.emccement.com

Here is a more technical explanation
http://www.emccement.com/Articles/EMC%20mechanism%20paper.pdf

When the cement industry says to the EU it cannot much reduce its energy / C02 imprint, well....

PS. cement kilns burn some very complex chemicals, and have only the legally demanded air filtration ... see
http://www.cank.org.uk (I wonder what happened to http://www.nack.org.uk/)

Sustainable Concrete Construction

biffvernon — Mon, 21 May 2007 21:24:42 +0100

Gosh, no magnets!