Can't help feeling that use of OPC must present some large technical advantages over using lime. Otherwise a) it wouldn't have been invented in the first place (why look for something different if lime already worked a treat) and b) wouldn't have become the dominant material which it has become. Obviously it is/was cheap to produce. It was also consistent in a way lime never really managed to be (though argubaly it could be now). It set much quicker and was essentially much stronger as a binder, which meant you could use less of it (something which limeys tend to overlook). Whilst cement production does contribute hugely to CO2 emissions (although an article in last weeks FT claimed that as an industrial product it was actually second behind steel), that is partly a reflection on just how much of the stuff we use. Switching over (back?) to lime doesn't really seem like much of a solution to me: it might produce a marginal improvement in CO2 emissions, but presumably at other greater costs elsewhere in the system. It would be more helpful to try and work on foundation-lite or foundation-free building techniques rather than just substituting cement with lime.

>>Come on you guys, lets start promoting Green Building.<<

There's the rubb Biff

I have received no reply to date from the cement suppliers you noted. So all we have established to date is that lime mortar may be a pretty 'Green' material for the mortar in brick walls.

Or is it?

Let's take a typical wall and look at the embodied energies:

Lime 1:2:9 mix Using ICE V5.1 works out at 0.198 kgCO2/kg
Cement/Sand: Again using ICE V5.1 works out at 0.228 kgCO2/kg

Typical wall: using commons: 83% brick, 17% mortar

Let's assume you are right and that the beds can be 50% but keep the vt joints at 10mm:
Lime wall: 90% brick: 10% mortar

So total using the same commmons at 0.2 is:
0.198 kg CO2/kg for lime
0.204 kg CO2/kg for normal

Lime a winner so far plus it will absorb (OK fairly nominal) CO2

So, for a typical building, let's say 6x8 with 2 skins over a 2 storey construction with 30% penetrations leading to 94sqm of wall:
Saving in CO2 = (0.204-0.198) x 94 x 2(skins) x 2200 x 0.103 and allow a lime bonus factor of 1.5

Saving = 383 kg of CO2 emissions

Now let's look at the typical embodied cost of this building using housing corp figures: We'll also use the HC's low end figures because it also makes lime's case look better:

Total cost = 500 (low end) x 6x8x2 = 48,000 kg

Now let's consider the impact if lime buildings, for any reason, turn out to have a 5% shorter lifespan:

Total cost = 48,000 x 5% = 2,400 kg

2400kg >> 383 kg

Lime not looking so good now

As pointed out above, there was a reason that we stopped building using lime. If we are to start using it for even the simplest of applications, such as mortars in walls, we first need to establish conclusively that it really is worth doing.

Second point is, as is fairly obvious from the above figures, embodied primary costs are not anywhere near as important as longevity for the external skins of residential buildings.

Sooo.....

OPC = Bad for environment
Lime = Not great for the environment

Answer ? = Use less of both, use Lime where technically feasible and/or explore other alternatives.


J

By the way can you reinforce lime for a reinforced raft foundation?

Have we factored in that lime is used in greater proportions often 1:3 where as opc is 1:6?

Yes Paul, we're talking mortar for house walls here, not concrete for wind turbine bases. Very different requirements.

If we're getting into the nitty-gritty of mortar ratios, a greener solution is to use more fines, silt and clay fraction, along with the coarse sand in the lime mortar. You don't need so much mortar. Try this next time you build a wall - 3 parts coarse unwashed sand, 1 part earth, 1 part hydrated lime. Should be good for a few centuries but if someone finds it's in the wrong place the bricks will be re-usable. It's also cheaper. Using materials avilable for free within wheelbarrow distance of the construction site has various advantages.

Tony, if you used a 1:6 OPC : soft sand mix there would be a lot of voids would there not?

Thought for today: building the new oil refinery at Jamnagar, India, invloves pouring 1.5million cubic metres of concrete. Think about it - 1 500 000 cubic metres.

Biff

Thanks for your comments.

I plucked random figures from Bath University's charts for comparison of common embodied materials. I used the best cases available for lime and the worst cases possible for cement. I am sorry that you think this is silly: I was trying to equate structural strengths and may indeed have been wrong in trying to do so.

There may be millions of buildings. There may be many with lime. There are very few very old buildings built with thin walls and a cavity that would meet current current regulations. This sounds to me like an argument that we should return to building ships in wood because HMS Victory is still around and there are no steel boats of the same age: QED.

You have convinced me that the case for lime is unproven and of little embodied consequence (if I entirely remove the embodied content of the lime and treat it as zero, the gain appears to be only 2500kg: To put this in context, according to Mark Whitby at RIBA last night, this is the equivalent of swapping about 8 lightbulbs for energy saving versions).

I thank you for that. I shall wait until more data is available before recommending lime on an environmental basis other than for its traditional use as a bedding mortar.

This has taken too much time for little gain. By joining this thread I was very much hoping that a proponent of the use of lime could provide some significant leads to allow its use in major applications rather than just a bedding mortar. There have been none. The technical lead supplied did not reply. So at this point I think it best to exit this thread.

Jon,
The OPC you refer to, would that be the same specification as use in the 70's ?.
I would presume(no proof) that the concrete used then, in road bridge construction would be of a much higher quality ?, Yet several on the M6 are having to be re-built due to concrete failure !. 2000 years on, now that's what I call progress.

The trouble with this "modern world" is we all want the latest technology, gizmos etc
and rapidly forget the past as "old hat". Architects have to have cutting edge designs or their clients move on.... specify clay bricks with lime mortar ...no way.

For sure there have been problems with OPC falling apart in the days before we understood about high alumina compositions and such like but that's history now and not a lot to do with the cement vs lime debate.

The essential thing is that for domestic building, houses of two or three storeys, with brick or stone walls, lime has a great many advantages over OPC, of which embodied energy and CO2 release are but two. It is really quite hard to see where OPC has any place at all in the housing field.

The 40% report did, of course, make some very unfortunate assumptions about refurbishing old houses. That rather discredited the report, which otherwise had some important things to say.

Posted By: jonBuilding Regs require 60 usuallly and timber frames can be stretched to 60 by careful wording of the maintenance requirements.

Hmm, 'careful wording'! I am a builder. I work with other builders. I am told by two regular colleagues who build timber-framed houses that 40 years is the lifespan of their buildings. I sure they do word the maintenance requirements carefully when they're signed off to the client, but 40 years is 40 years.
And when you talk of building regs, do you mean the approved documents or the statutory requirements? I know of no requirement to have thin walls and a cavity, but I'm prepared to be corrected if you could point me in the right direction.
Anyway, I glad we were able to convince you so conclusively of the inappropriateness of lime. For further proof of how useless it is in new builds, take a look at the BRE Haverhill experiment, and also Ian Pritchett's work with lime and hemp in structural panels. They will certainly prove to you utterly and conclusively how OPC is the only really green material one should consider.

Gervaise

40 years: There are lots of centuries old timber framed houses around today that are much older than houses built with lime mortar.

I am, of course, being disenginious. I do understand exactly what you are talking about even if I disagree a little with your quoted lifespan figures for timber frames.

Rephrasing my statement regarding cavities might also be thought of as disenginous?

There is no requirement to have a cavity. There are many requirements that make such a cavity the least expensive solution for current day materials when used to meet current standards. Even then, cavity walls are a high embodied solution. As are walls built with lime mortar: The lime may be a low embodied solution but the remaining 90% of the wall is not.

Rephrasing my statement regarding lime might also be thought of as disenginous?

Rephrasing my statement regarding OPC might also be thought of as disenginous?

As mentioned earlier, I think it best not to contribute further to this thread.

Mud.

(No mud-slinging)

water content/ organics, fines, lumps, stones etc.....
Yep, you'll need all of that (not too many stones for fine work) plus some straw. Remember the most important specification is that the material has to come from within wheelbarrowing distance of the site. Use what there is and get out of the modern measuring mindset. It will work.

>we train builders to a lower level than on the continent

I've noticed in French builders merchants one is confronted with stacks of lime of various varieties, hydrated and a range of hydraulics, and then tucked round the corner a small pallet of cement bags.

I have two comments – one regarding the lime-CO2 issue discussed by Jon at the beginning, and the second regarding the deleterious effect of OPC on sanstone and limestone structures.

1. Lime CO2 absorption is non-trivial

I have been using lime for 14 years restoring my French chateau- its now 600+ years old, constructed from sandstone ashlars and lime, and is still going strong!

The major problem that the 21st Century faces is that everyone is in too much of a hurry - everything has to be done yesterday, and to some extent cement allows this impatience with traditional (and green) methods to be put aside in this rush to finish.
Bifvernon has raised the issue of OPC versus lime re CO2, and the following may help to clarify the reasoning:

Lime has many advantages - which I discussed on the earlier incarnation of this forum - especially the fact that upon curing lime absorbs atmospheric CO2 in a non-trivial way.

To manufacture lime we burn calcium carbonate (limestone e.g chalk):

CaCO3 +1200C + Heat = CaO + CO2

the CO2 going off into the atmosphere. (N.B. 100.08 tonnes of CaCO3 contains 56.08 tonnes of CaO, calcium oxide and 43.98 tonnes of CO2)

When lime mortar is made, the setting process is the reverse of the above reaction:

CaO+CO2 = CaCO3,

and for every 560.8 tonnes of CaO used, 43.2 tonnes of CO2 is reabsorbed from the atmosphere, so that the 'only’ energy used in is manufacture is that when heating CaCO3 to about 1200C to drive off the CO2, as above. Jon has already shown that this is rather smaller than that used in the manufacture of OPC. Here in France we have the additional advantage that the electrically driven kilns as St Astier use electricity from nuclear reactors – far cleaner than either oil or coal or gas, and with minimal CO2 production.

Therefore lime and especially French lime is very GREEN when compared to OPC, and has a proven record of structural integrity over, in some cases, millennia. All the building still standing that were built before about 1820 attest to the durability of lime mortar! I noted in my last visit to B&Q that most of the cement was of Chinese manufacture – how cheap is that to manufacture and transport in CO2 terms???

Another issue that is seldom discussed in this forum is the use of natural as opposed to manufactured materials , that is, stone versus bricks, concrete block etc. Brick manufacture used large amounts of energy during the burning process, as does concrete blocks from OPC.

Green building should only be using natural materials when available. The extensive use of bricks and concrete blocks is due to the loss of traditional skills using stone, the bias of architects, and ease and rapidity which 'modern' building methods allow - again the 21st C 'rush problem'.

I wonder how many buildings using modern materials will be still standing in 500 years - very few I imagine.

2. OPC and natural building stone deterioration
Aside from the issue of energy and CO2 release, another factor is the impact of OPC on traditional stone buildings. With few exceptions, the juxtaposition of OPC with porous geological materials such as sandstones and limestones is destructive of the stonework due to the differences in the water retention and porosity of stone, lime and OPC.
Generally speaking, stone and lime have similar porosities, so that evaporation of soil water, groundwater and rainwater taken up by the stone through capillary action is usually readily evaporated when dry conditions prevail.
The behaviour during frosts and freezing conditions is similar, so that water is not generally retained within the structure, and especially not above the horizontal joints in the stonework, when lime is used.
When OPC is used for bedding/jointing, the imperviousness of OPC means that water is retained above the jointed surfaces of the stonework,, so that frost and freezing causing expansion of this H2O and spalling of the stone arises, retreat of the stone face above the OPC joints, and the development of concavities immediately above the OPC joins resulting in further and easier water ingress into the building fabric.

I’ve seen many examples here in France of English owners ruining beautiful old traditionally lime pointed walling and ashler stonework by using OPC. The colour of OPC is also dead, unlike properly made lime using local (and original) naturally coloured sands.

The English Heritage books by Prof Ashurst are a good source of more specific information on the use of lime in stone buildings.

You worry me again with time scales it can take 100 years for lime to reabsorb all the CO2.