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

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

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.

Whattt? That sounds like water running uphill.

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.

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.

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

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.

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).

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.

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.

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.

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?

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.

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.