Green Building Forum - Cement v Lime

Cement v Lime

Mike George — Tue, 16 Oct 2007 20:19:51 +0100

There is plenty of condemnation on the forum regarding anyone who dares to suggest using cement. While I understand that cement has a huge environmental impact, just how much better is lime?

Firstly there is the process. How does Lime compare with cement in terms of energy needed for production?
Secondly, how does lime compare in terms of energy use in transportation? Is there much lime produced in the UK?
Finally, what are the dangers to health of each?

Anyone care to take a stab at some figures, just wanting to further my knowledge

Cement v Lime

James Norton — Tue, 16 Oct 2007 20:40:02 +0100

Mike,

See below:

http://www.buildingforafuture.co.uk/autumn05/ordinary_portland_cement.pdf
http://www.greenspec.co.uk/html/materials/cementsub.html

also:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=690&page=1#Item_17

J

Cement v Lime

Mike George — Tue, 16 Oct 2007 21:01:05 +0100

Thanks James, I have not seen any of those- some reading to do!

Cement v Lime

James Norton — Tue, 16 Oct 2007 21:16:58 +0100

Mike,

From what I know of OPC, it is generally pretty much a disaster zone all round: C02 producing reaction, that need loads of energy to get started, huge materials extraction, then we use tons and tons of it and transport it all over the country, also local pollution at cement works and on site.... however I don't think that lime is the panacea that its perhaps made out to be, still uses energy to produce (albeit less) and transport... also not sure how long a 2m deep Limecrete trench foundation needs to cure...

The info above did give me some interesting reading though, particularly looking at PFA, Eco-cement and Hempcrete. CAT have also done work on designing out the need for cement. The use of cement/and cement alternatives seems somewhat linked to thermal mass and lightweight vs heavy weight design, the latter tending to need more of the stuff. My big thing at the moment is looking for ways of including thermal capacity with less cement, ie earthen screed/plasters and strategic placement of mass within a super-insulated lightweight frame for eg. Although every thread I've started so far seems to be overcome by a discussion about insulating/or not ground bearing slabs, wing insulation etc etc!

J

Cement v Lime

fostertom — Tue, 16 Oct 2007 21:57:46 +0100

This got some airing at the Tradical Hemcrete seminar I attended at Eden project. The lime binder, which was developed with much research etc so as to actually work, does contain some cement as well as other secret ingredients. It's distributed by Castle Cement, which is part of Heidelberg Group, Europe's biggest cement producer, who claim to create less CO2 per tonne than anyone else, and falling. As far as they are concerned, there's no limit to their progressive reduction of fossil fuel in cement production. Whether this is because they're burning car tyres, rubbish etc instead of oil/coal, I don't know - if so that's cheating because all that should be rercycled as raw material, not burnt.

Cement v Lime

tony — Tue, 16 Oct 2007 23:11:02 +0100

One problem with lime is that unusually it gets more radioactive with time! All other things get less radioactive.

Cement v Lime

fostertom — Tue, 16 Oct 2007 23:50:17 +0100

Whattt? That sounds like water running uphill.

Cement v Lime

Terry — Wed, 17 Oct 2007 03:30:36 +0100

Read somewhere that cement production needs over 1600 deg c temperatures whereas lime is around 1100 to 1200. Cant find my source at the moment though.
Would be interesting to know how much lime is actually produced in the UK - I believe a lot of what is available is transported in from France. If this is the case, definite room for improvement.

Cement v Lime

biffvernon — Wed, 17 Oct 2007 07:55:19 +0100

Mike, if you want figures try asking the techies at Singleton Birch, Lincolnshire. They are very keen to educate people. They are one of the larger UK lime producers.

Hydraulic lime cures underground but, James, why on earth, or under earth, would you want a 2m deep Limecrete trench foundation? When building houses with lime mortar, ridgid foundations are not needed. It doesn't crack with movement like OPC mortar.

Green Building does not require cement since it does not include high-rise towers, motorway flyovers, airport runways and nuclear containment vessels. Most other stuff can be done with lime, or even earth.

Cement v Lime

jon — Wed, 17 Oct 2007 08:15:12 +0100

Biff

Green Building does not require cement since it does not include high-rise towers,...<

There is a great deal of controvery about this. As a society we must decide if we want to build lots of low density 'green' housing in green belt with the possibility of power generation or.. whether we go for dense cities with compact units and low U value units.

Some would say that the latter is truly green as it does not impact the countryside.

Cement v Lime

jon — Wed, 17 Oct 2007 08:30:51 +0100

For high durability and structural items of a similar ilk, the debate is, to some extent pointless. With lime we are yet to find out if there are any significant problems with its properties (such as carbonation or creep). OPC has many problems such a ASR, carbonation, chloride penentration, creep and so on. These are all known and quantified.

If the properties of lime cements prove to make that cement a short term material for any of the major cement applications then any gains made now in reducing carbon production impact will be completely destroyed later by the amount of rebuilding that will be required: The negative impact of rebuilding compared to the initial savings made in CO2 amelioration would be exceptionally severe.

For items of a low stress and durability nature, such as floor slabs particularly when treated with hardeners, there is a much better argument for limes.

Cement v Lime

DrJon — Wed, 17 Oct 2007 09:49:52 +0100

Both lime and cement incur carbon penalties in their manufacture and distribution, but it can be difficult to persuade building inspectors that it is safe to use anything else in foundations. One realistic approach to minimise the impact is to use a substitute slicate binding agent - ground blast furnace slag (GBFS) and pulverised fuel ash (PVA) are both options that would otherwise be used for landfill. PVA has traditionally been used to relace around 20-30% of the cement/lime, although anything up to 50% seems OK. GBFS is particularly efficient in this regard and can replace up to 90% of portland cement in a foundation mix (not sure about the proportions when mixed with lime). Manufacturing portland cement generates around 950g CO2/kg, lime around 450g/kg and GBFS 100g/kg. Transport will typically add around 30-50g/kg for each of them. Thus (and ignoring the CO2 attributable to the aggregate) a typical strong concrete mix will generate around 300g/kg if made with pure cement, around 135g/kg with lime and around 60g/kg if made with cement/GBFS in a 90% mix. These figures are only estimates, but give a fair representation of relative CO2 performance. The GBFS mix also has the advantage that it will go off as quickly as a conventional portland mix.

Cement v Lime

jon — Wed, 17 Oct 2007 10:55:32 +0100

Good points Dr Jon. I would be a bit wary of going to 90% GBFS though (70% seems a more commonly used figure)

Cement v Lime

biffvernon — Wed, 17 Oct 2007 11:31:44 +0100

Posted By: jonWith lime we are yet to find out if there are any significant problems with its properties

Crazy. OPC was in vented in the mid 19th century and only widely adopted in the 20th century. Lime has been used for many hundreds of years - we know how it works over time.

High density urban living is possible (should it be deemed desirable) without towers that require OPC.

GBFS and PVA have useful properties and while available we may as well make use of them but they are by-products of unsustainable industries and so should not be regarded as a significant part of Green Building. Once we realize how much global warming is a problem coal mining will be outlawed and PVA will become a historic material.

Difficulties in persuading building inspectors about foundations is a lame excuse. The Law does not require the use of OPC and it's up us to show that it's not needed. My house was not built with any OPC and it's been standing for 250 years.

Once again I am amazed that people posting on this forum don't seem to have read the title - Green Building Forum. We should be saying there is no place for OPC in domestic building. Reserve it for specialist applications such as bases of wind turbines and the facing of the Severn Barrage. The cement industry is the most damaging single industry on the planet, beside which air travel is insignificant.

Cement v Lime

jon — Wed, 17 Oct 2007 11:57:52 +0100

Reasoned debate is a useful contribution one can make to Society. Your views of what 'Green' means are not necessarily correct. Although I agree with some of your views, trying to impose one's own perspective on Society without adequate reference to proven data is usually a lost cause.

Cement v Lime

biffvernon — Wed, 17 Oct 2007 13:48:15 +0100

I made five points in my previous post. I'm so glad you agree with some of my views, Jon. Which ones? If you tell me where we differ I'll attempt to seek the data to support my position. I've already pointed to where data regarding one of Mike's questions might be found. I'm afraid I can't quite see how a 'Green' view can easily be regarded as 'correct'. Greeness is not black or white.

Cement v Lime

fostertom — Wed, 17 Oct 2007 14:10:58 +0100

Posted By: biffvernonThe cement industry is the most damaging single industry on the planet, beside which air travel is insignificant

Precisely - when people get all self-congratulatory about how they've given up air holidays, just say they'd do better to give up cement and concrete - gives pause for thought!

However, does the cement industry's need for process energy really make it irredeemable?

Posted By: Terrycement production needs over 1600 deg c temperatures whereas lime is around 1100 to 1200

Unavoidably, heating tonnes of material to that temp requires masses of energy. But:
a) what is that energy was sustainably sourced - biofuels, wind/wave/hydro/PV electricity etc?
b) what if that energy came from burning wastes that wd otherwise have been landfilled - tyres, rubbish etc - which is indeed the line that's being presently developed - but this stuff shouldn't be burnt, it should be carefully stockpiled (aka landfilled) until shortage of materials and new extraction technology turns it into rich source of future raw materials http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=144 (unfortunately the article linked to seems to no longer be on The Independent's site but I'll see if I can OCR my copy if anyone's interested).
c) what if the energy could be captured and directed to where fuel would have otherwise been burnt?

Too many self-satisfied blanket statements about this is a sin, that is a crime, based on hitherto-experience, instead of focusing on visionary change (which rightly includes high technology).

Cement v Lime

jon — Wed, 17 Oct 2007 14:48:54 +0100

Rather then deal with multiple points, it is probably best to work through one at a time:

Your first point appears to be that lime has been used for centuries and refer to Singleton Birch, Lincolnshire for more information. The site appears to be a manufacturer's site rather than a technical reference. There appear to be no technical references to any academic bodies or research institutions on that site.

If you can refer to one or more papers by a University or similar trustworth institution showing the research undertaken to prove that lime cement will have no detrimental impact when used for modern day applications: No chemical implication such as ASR or silicate or chloride interaction, no carbonation and associated ingress difficulties, no excess creep, no strain imbalances when used compositely, suitable contraction properties, suitable expansion properties under temperature and moisture and no impact under groundwater acidity attack.

The papers that you will provide can be used to persuade the Building Inspectors that it is, after all, suitable for the purpose.

I look forward, with great interest, to seeing the references.

Cement v Lime

biffvernon — Wed, 17 Oct 2007 17:51:25 +0100

Jon, I didn't say go to a website, I said, "try asking the techies at Singleton Birch". I happen to know that their technical staff are very happy to supply information about their manufacturing processes. I've been on a tour of the plant and found it very instructive.

I'm not sure what you mean by "modern day applications". I'm talking about buildings for humans to live in, aka houses. My house, built with lime mortar 250 years ago, doesn't suffer from any of the ailments you list. I can't see why we should not use this tried and tested method of building. It would be a lot greener than much of the rubbish that is built these days.

I would regard the Society for the Protection of Ancient Buildings as a trustworthy institution, a lot more trustworthy than many in the construction industry.

Cement v Lime

jon — Wed, 17 Oct 2007 18:21:29 +0100

Biff

Thanks: I have gone to Singleton Birch to ask the question. It would be marvellous if they did indeed have references that could be used.

Modern day applications would bring us on to the second point that I disagree with early. Modern appplications I think means construction methods suitable for today's standards, workforce and construction environment.

I would not regard the Society for the Protection of Ancient Buildings as a suitable academic source for research information unless they have actually done the research. I can not see why the SPAB would have done research into modern construction uses for lime when their remit seems to concern the Protection of Ancient Buildings.

We shall wait for a few days to see what response comes from Singleton Birch?

Cement v Lime

Gervase Webb — Wed, 17 Oct 2007 19:37:34 +0100

Posted By: jonFor high durability and structural items of a similar ilk, the debate is, to some extent pointless. With lime we are yet to find out if there are any significant problems with its properties (such as carbonation or creep).

There are some buildings that have been standing for around 2000 years - the Pantheon in Rome being just one. That's not a bad testament to the durability of limecrete.

Cement v Lime

fostertom — Wed, 17 Oct 2007 19:59:52 +0100

I thoght the Romans were using concrete?

Cement v Lime

Gervase Webb — Thu, 18 Oct 2007 07:54:58 +0100

Roman concrete was lime-based with an effective pozzolan (the name coming from the small town near Vesuvius which supplied the volcanic ash used to accelerate setting) - very different from modern cement-based concrete, which is fired at far higher temperatures and which does not reabsorb CO2.
Modern concrete is wondeful stuff - it has extraordinary strength and can be cast more easily than limecrete. But, as Biff says, for a lot of ordinary building it's unnecessary overkill.
The compressive forces at the base of the structural walls of a two-storey house are between five and seven Newtons. Modern concrete has a compressive strength of up to 70 Newtons. There is no reason why hydraulic limes shouldn't be used for such construction. And, thankfully, more and more architects, builders and specifiers are realising this.

Cement v Lime

biffvernon — Thu, 18 Oct 2007 08:06:37 +0100

Posted By: jonModern appplications I think means construction methods suitable for today's standards, workforce and construction environment.

I rest my case

Cement v Lime

jon — Thu, 18 Oct 2007 08:44:24 +0100

Gervaise

The additional advantage of the pantheon lime pozzalan concrete was that it appears to have a high tensile strength: Very useful for asymetric load cases structures in addition to the ability of the lime to deform. The Romans probably constructed using a very low water content with workers intricately tamping in each section to allow each small section of cast to have not fully set by the time the next layer was introduced: Perhaps the pozzalans also help in allowing the joint casts to develop full strength?

Cement v Lime

James Norton — Thu, 18 Oct 2007 08:47:39 +0100

Biff,
RE: 2m trench footings: perhaps an extreme example, but you've raised in my view the main issue here, which is that massive quantities of lime or cement are bad for the environment and that a wider view should b taken to design out the need. In that massive context Limecrete can still be pretty bad for the environment, its just better than concrete.

This is a challenge particularly in buildings other than houses where imposed loads can be much higher and on sites with variable ground conditions, and where walling materials have tighter tolerances, (but of course the tolerances of the walling is of course just an extension of the same issue).

Does anyone have any experience of reinforced limecrete, I'm thinking here about reinforced strip footings and reinforced raft foundations particularly.

J

Cement v Lime

jon — Thu, 18 Oct 2007 08:55:08 +0100

Biff

"I rest my case"

There may well be a case for a return to an agrarian society, which appears to be what you are advocating, but if that case cannot be explained in a way that anyone can understand, it will not be taken seriously.

Cement v Lime

James Norton — Thu, 18 Oct 2007 08:57:41 +0100

Easy tiger!

Cement v Lime

jon — Thu, 18 Oct 2007 09:12:04 +0100

Hi James

Yes, must do some work rather than write here! I'll edit it a bit before doing so. I would love to be able to use limecrete but without real information it is difficult to see how that will happen. To me it appears that arguments for environmentally based materials based on faith rather than reality do more harm than good.

Also worth noting that damage to the environment caused by CO2 production of any material is also inversely proportional to the longevity of the item. Other than subsistence farming structures, the Pantheon, a concrete structure, has probably had one of the lowest annualised CO2 impacts on the planet.

Cement v Lime

blacksmith — Thu, 18 Oct 2007 10:42:42 +0100

Apologies - not hijacking the thread but seems to be of interest to the cement v lime angle - Any one on here from CAT can shed some light on the failed use of hempcrete (I think) that had to be replaced by concrete last week?

Gareth