Green Building Forum - Is it acceptable to use Ordinary Portland Cement [OPC]?

Is it acceptable to use Ordinary Portland Cement [OPC]?

ted — Mon, 02 Jun 2008 19:16:39 +0100

Anyone know the current BRE stance on mixed OPC and lime mortar?

They were dead against it a few years ago.

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Mon, 02 Jun 2008 22:03:39 +0100

Posted By: tedAnyone know the current BRE stance on mixed OPC and lime mortar?

They were dead against it a few years ago.

Don't know, but the British Standard for external rendering in areas of severe exposure recommends various combined mixes. Most common from memory is 5 Sand: 1 cement : 1 Lime

Presumably those who wrote it know what they are talking about.

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Mon, 02 Jun 2008 22:13:41 +0100

I can't find my copy but I believe its this one, dated 2005
http://www.bsi-global.com/en/Shop/Publication-Detail/?pid=000000000030139915

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Mon, 02 Jun 2008 23:43:56 +0100

Ted, this from the BRE Good Building Guide 18 [1994] I cannot find a newer BRE document.

Rendering mixes which meet the designations (I, II, II, IV) These are for use on varying backgrounds and exposure much the same as those listed in the British Standard. They are

Type I] 1 OPC: 0.25 Lime: 3 Sand
Type II] 1 OPC: 0.5 Lime: 4 to 4.5 Sand
Type III] 1 OPC: 1 Lime: 5 to 6 Sand
Type IV] 1 OPC: 2 Lime: 8 to 9 Sand

The guide gives other suitable Type I-IV mixes for cement readymix; cement : sand [with air entraining agent]; and Masonry cement: sand. Note these latter mixes contain no added lime.

Each of the following backgrounds is recommended to be rendered with one or more of the types listed above: This varies by coat as well as exposure/background

Clay and Calcium Silicate brickwork
Dense Concrete bricks and blocks
Lower density concrete and concrete blocks
Textured concrete
Cast key surface concrete
Smooth concrete and stone
Timber framed walls [with metal lathing]
Steel frame walls [externally insulated and with metal lathing]

All of the above utilise OPC

Cob is the only wall/background type listed which does not contain a suitable OPC mix as an option. Straw bale is not mentioned

With reference to Lime, BRE GPG18 says

'For most purposes hydrated lime to BS890 is acceptable. Lime is added to increase workability and cohesiveness of a mix; it also helps to reduce the risk of shrinkage cracking'.

It goes on to say 'Advice is available on Lime putty and limewashes for cob walls' [Ref 3 DEBA Devon Earth Building Association]

Is it acceptable to use Ordinary Portland Cement [OPC]?

biffvernon — Tue, 03 Jun 2008 08:24:24 +0100

Jon said >It may be worth your while reading about the subject if it interests you.

Here are a few of the online articles I've read over the last few years. Perhaps everyone should follow Jon's suggestions and do a little reading before continuing this debate.

Graham O'Hare, Lime Mortars and Renders: The Relative Merits of Adding Cement; http://www.buildingconservation.com/articles/cement/cement.htm
Peter Ellis, Gauging Lime Mortars; http://www.buildingconservation.com/articles/limegauging/limegauging.htm
Bob Bennett, The Development of Portland Cement; http://www.buildingconservation.com/articles/prtlndcmnt/prtlndcmnt.htm
Jonathan Taylor, Lime: The Basics; http://www.buildingconservation.com/articles/limebasic/limebasic.htm
John Ashurst, The Technology and Use of Hydraulic Lime; http://www.buildingconservation.com/articles/lime/hylime.html
Ian Constantinides, Traditional Lime Plaster: Myths, Preconceptions and the Relevance of Good Practice; http://www.buildingconservation.com/articles/plaster/plaster.htm
Ian Pritchett, An overview of buildinglimes; http://www.ihbc.org.uk/context_archive/54/overviewlimes_dir/overviewlimes_s.htm
Mike Wye, Hydraulicity in lime mortars; http://www.ihbc.org.uk/context_archive/63/limemortars/hydraulicity.html
Pat Gibbons, Pozzolans for Lime Mortars; http://www.buildingconservation.com/articles/pozzo/pozzo.htm
English Heritage, AC1 Smeaton project on historic mortars durability; http://www.uvm.edu/histpres/203/eh/RESEARCH1.HTML
Jeanne Marie Teutonico et al., The Smeaton Project: Factors Affecting the Properties of Lime-Based Mortars; http://www.jstor.org/pss/1504464 (sub required)

And in case you miss it, here are a couple of paragraphs from Graham O'Hares' paper which just caught my eye:

"DISADVANTAGES (of guaging lime with OPC)

â€¢the rapid setting time limits the time available to the user in which to work with the gauged mortar
â€¢some cements contain appreciable amounts of soluble salts, in particular potassium sulphate, which may become a source of salt damage to stonework
â€¢the use of cement tends to lead to the user treating the gauged lime mortar as if it were a fully hydraulic lime or cement. Too much reliance on the initial chemical set leads to neglect of the importance of the longer term carbonation of the non hydraulic component present
â€¢the danger that segregation occurs, whereby the cement separates from the lime as the mortar dries and hardens.

"Segregation is a major hazard of gauging lime mortars with cement. As the mortar sets, the cement colloid tends to migrate into the pores of the lime mortar as they form, clogging them and leading to a greatly reduced porosity. If the proportion of cement is high enough, segregation is much less likely to occur, but the resulting mortar will be hard. If the cement proportion is low, the mortar will be less hard, but segregation is more likely to occur. The resulting mortar will be seriously weakened, with a poorly formed pore structure leaving it very susceptible to frost damage and deterioration, even after carbonation of the non hydraulic lime present has taken place.

"The Smeaton Project, a research programme commenced by English Heritage indicates that a 1:1:6 mix, containing a 50 per cent cement binder, is unlikely to segregate, while a 1:2:9 mix, containing a 33 per cent cement binder, is almost certainly at risk. Until recently it was considered good practice to gauge lime mortars with as little as 5 per cent cement, just enough to impart a chemical set but not enough to make the mortar appreciably harder. However all of the Smeaton Project test samples containing less than 25 per cent failed.

"Given the possible hazards of segregation, an un-gauged lime mortar relying solely on carbonation is likely to be more resilient in the long run than one gauged with a small amount of cement. This will require care in its application and careful nurturing to ensure that it carbonates properly. If a chemical set is required, a safer alternative would be to use an hydraulic lime. In these the hydraulic components are so closely associated with the non hydraulic that segregation does not occur. These tend to be hard and impermeable, but not usually as hard as a 1:1:6 mix. Brick dust is a cheap and highly effective pozzolanic additive, providing a useful alternative to cement."

Is it acceptable to use Ordinary Portland Cement [OPC]?

ted — Tue, 03 Jun 2008 09:28:29 +0100

Mike,

in November 2005 BRE issued GBG66 'Building masonry with lime-based bedding mortars' which says:

Hybrid mortars comprising OPC, lime and sand have been used quite widely but such mixes with a low OPC content
tend to have poor durability compared with well-designed HCL and HL mixes and are not now recommended.

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Tue, 03 Jun 2008 19:46:54 +0100

Posted By: biffvernonJon said >It may be worth your while reading about the subject if it interests you.

And in case you miss it, here are a couple of paragraphs from Graham O'Hares' paper which just caught my eye:

"DISADVANTAGES (of guaging lime with OPC)

â€¢the rapid setting time limits the time available to the user in which to work with the gauged mortar
â€¢some cements contain appreciable amounts of soluble salts, in particular potassium sulphate, which may become a source of salt damage to stonework
â€¢the use of cement tends to lead to the user treating the gauged lime mortar as if it were a fully hydraulic lime or cement. Too much reliance on the initial chemical set leads to neglect of the importance of the longer term carbonation of the non hydraulic component present
â€¢the danger that segregation occurs, whereby the cement separates from the lime as the mortar dries and hardens.

"Segregation is a major hazard of gauging lime mortars with cement. As the mortar sets, the cement colloid tends to migrate into the pores of the lime mortar as they form, clogging them and leading to a greatly reduced porosity. If the proportion of cement is high enough, segregation is much less likely to occur, but the resulting mortar will be hard. If the cement proportion is low, the mortar will be less hard, but segregation is more likely to occur. The resulting mortar will be seriously weakened, with a poorly formed pore structure leaving it very susceptible to frost damage and deterioration, even after carbonation of the non hydraulic lime present has taken place.

"The Smeaton Project, a research programme commenced by English Heritage indicates that a 1:1:6 mix, containing a 50 per cent cement binder, is unlikely to segregate, while a 1:2:9 mix, containing a 33 per cent cement binder, is almost certainly at risk. Until recently it was considered good practice to gauge lime mortars with as little as 5 per cent cement, just enough to impart a chemical set but not enough to make the mortar appreciably harder. However all of the Smeaton Project test samples containing less than 25 per cent failed.

"Given the possible hazards of segregation, an un-gauged lime mortar relying solely on carbonation is likely to be more resilient in the long run than one gauged with a small amount of cement. This will require care in its application and careful nurturing to ensure that it carbonates properly. If a chemical set is required, a safer alternative would be to use an hydraulic lime. In these the hydraulic components are so closely associated with the non hydraulic that segregation does not occur. These tend to be hard and impermeable, but not usually as hard as a 1:1:6 mix. Brick dust is a cheap and highly effective pozzolanic additive, providing a useful alternative to cement."

Biff, rather a selective quotation that, perhaps you need to take Jon's advice as well To put your quote into context, this, from the same 'paper'

''There are, as one would expect, both advantages and disadvantages in gauging non hydraulic mortars with cement to make them hydraulic.

ADVANTAGES

â€¢it imparts a chemical set which occurs before full shrinkage occurs, thereby reducing the risk of cracking

â€¢layers may be built up more rapidly, without the need to wait a long time for one to set fully before applying the next

â€¢it hardens rapidly, thereby providing protection from rain before carbonation has been completed. This helps to beat the inclement British weather

â€¢being an artificial substance manufactured under closely controlled conditions, it is reliable and predictable in use

â€¢it is available in a choice of colours, useful when it is necessary to match the colour of an existing mortar or render. ''

The other references you offer seem to relate to historic buildings, and I do agree with you in that the wrong kind of OPC mix can be detrimental to historic fabric.

However, this does not mean that it is unacceptable to use OPC persay. Indeed the British Standards and BRE guidance indicate that OPC is suitable for use as in my previous posts.

I would be very interested to read publications which contradict BRE GPG18 regarding the use of OPC for RENDERING in buildings other than those of significant historic value. ie. those which are listed.

By the way, I have been using combined OPC and Lime mixes for more years than I care to remember. My experience tells me that the recomandations in BRE GPG18 work very well in practice.

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Tue, 03 Jun 2008 19:54:23 +0100

Posted By: tedMike,

in November 2005 BRE issued GBG66 'Building masonry with lime-based bedding mortars' which says:

Hybrid mortars comprising OPC, lime and sand have been used quite widely but such mixes with a low OPC content
tend to have poor durability compared with well-designed HCL and HL mixes and are not now recommended.

Ted, Having read this, I can see that this advice is given in a context relating to bedding mortar; and largely concentrates on recomendations for the use of such mortars in Conseravation work.

I don't accept that it contradicts the guidance for RENDERING in GPG18. Its apples and oranges.

Is it acceptable to use Ordinary Portland Cement [OPC]?

biffvernon — Tue, 03 Jun 2008 20:45:11 +0100

Posted By: Mike George

Biff, rather a selective quotation that, perhaps you need to take Jon's advice as well<

Of course it's selective. I selected it from one of the ten papers I linked to for no better reason that, as I said, it caught my eye, and it seemed relevant particularly for folk who didn't want to wade through hours of reading.
As for taking Jon's advice, if I didn't have a hide thicker than the average mastodon, I'd have been insulted by such patronising nonsense. I have, of course, read every word of each of those papers over the last few years. Yes, I'm mostly interested in historic buildings, but that includes building new stuff in such a way that it stands a chance of becoming historic one day. Lime has stood the test of time and proved up to that job. And it doesn't result in so much CO2 pollution.

I just don't see why one should want to defend OPC. It's one of the many practices that makes the modern building industry such rubbish. What is it with you guys?

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Tue, 03 Jun 2008 22:22:02 +0100

Miaaaaaw, put yr claws away - there are often patronising comments used on this forum. It seems that some folk will use just about any tactic to get their point across, from spin to ridicule to rudeness to outright lies. I tend to offer a little banter in return rather than getting upset - I too have thick skin

Seriously though Biff, you are not the only one who has read around this area significantly, we each have an opinion based on practical experience and/or research - I respect yours and agree with your stance on the use of Lime in Historic buildings.

In the real world though OPC is a necessity, whether you like it or not.

Is it acceptable to use Ordinary Portland Cement [OPC]?

biffvernon — Wed, 04 Jun 2008 07:39:59 +0100

"OPC is a necessity", but you haven't said why, other than speed of build, and as I admitted, for strength in steel reinforced beams and suchlike, most of which we can probably do without.

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Wed, 04 Jun 2008 08:03:37 +0100

Posted By: biffvernon"OPC is a necessity", but you haven't said why

Yes, I have, as have others on this thread. The quotation from your own paper sums up the practical reasons nicely.

In environmental terms, the issues are complex and amount to far more than any one aspect, such as destruction of habitat caused through quarrying; transportation; energy use in the kiln; health and safety etc.

If either OPC or lime is used less, the other will be used more, resulting in an increase in the negative aspects associated with that material. Then we would need to factor in the implications of the practicalities in use referred to above, to assess their respective impact as well. A simple example is the respective time taken to complete a particular job, and how much travelling back and forth is associated with it. Is this a big deal? well it is if your newly rendered wall is frost damaged or washes off in the rain before it has time to set.

That's before you consider cost impications

Is it acceptable to use Ordinary Portland Cement [OPC]?

jon — Wed, 04 Jun 2008 10:00:33 +0100

" I'd have been insulted by such patronising nonsense."

It wasn't meant to be patronising Biff. Time is short for all of us. The subject discussed was carbon and the relative embodied carbon impacts. The numerous articles you have posted seem to be on the technical use of mortars.

As a leading proponent of lime on this forum it seems to me that it would be in your interest to read about this subject as this argument will impact adversely on the case for using lime: I had it cited to me yesterday in the Pub by a young engineer. He didn't, of course, realise that I wrote all the original technical arguments that were being quoted to him.

Is it acceptable to use Ordinary Portland Cement [OPC]?

biffvernon — Wed, 04 Jun 2008 11:50:57 +0100

If...I'd have been...but I'm not...so I wasn't :)

Do stop advising me to read even more, Jon, unless you can suggest something useful on the subject that I haven't already read.
I did post a link to a site that showed you how to do the arithmetic regarding CO2.

Mike, you've repeated the time of setting advantage of OPC, but what else is there?

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Wed, 04 Jun 2008 12:06:12 +0100

Repetition:

ADVANTAGES

â€¢it imparts a chemical set which occurs before full shrinkage occurs, thereby reducing the risk of cracking

â€¢layers may be built up more rapidly, without the need to wait a long time for one to set fully before applying the next

â€¢it hardens rapidly, thereby providing protection from rain before carbonation has been completed. This helps to beat the inclement British weather

â€¢being an artificial substance manufactured under closely controlled conditions, it is reliable and predictable in use

â€¢it is available in a choice of colours, useful when it is necessary to match the colour of an existing mortar or render. ''

Is it acceptable to use Ordinary Portland Cement [OPC]?

biffvernon — Wed, 04 Jun 2008 13:54:09 +0100

>â€¢it imparts a chemical set which occurs before full shrinkage occurs, thereby reducing the risk of cracking
That's true. Rendering in lime requires a modicum of skill to avoid shrinkage cracks. OPC just cracks later when the building settles (Oh! You've built a massive ridgid concrete foundation in the hope of preventing that.)

>â€¢layers may be built up more rapidly, without the need to wait a long time for one to set fully before applying the next

>â€¢it hardens rapidly, thereby providing protection from rain before carbonation has been completed. This helps to beat the inclement British weather

Yes, we know about speed.

>â€¢being an artificial substance manufactured under closely controlled conditions, it is reliable and predictable in use
Very similar to modern lime production, the two processes are similarly controlled. No advantage there then. Of course in the old days, local lime production gave character to buildings, something that is lost in mass, standardized production.

>â€¢it is available in a choice of colours, useful when it is necessary to match the colour of an existing mortar or render.
You can colour lime in just the same ways. No advantage there then.

So, we're just left with speed. I'm told MacDonalds do fast food but I wouldn't know, I'm a member of the Slow Food Convivium: http://www.slowfood.org.uk/uk.html

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Wed, 04 Jun 2008 17:14:50 +0100

Wow, first you advocate a reference to justify your stance, quoting the bits you like. Then, when faced with the bits you don't like, you manage to spin them into something that you do. I bow to your masterfull interpretation.

I'm going to let someone else have a go now, [that is until something new is forthcoming] Also a final thought regarding the pole results so far. If they are like this on the Green Building Forum, imagine what they would be like on Wimpratt.com

Is it acceptable to use Ordinary Portland Cement [OPC]?

jon — Wed, 04 Jun 2008 17:42:53 +0100

Quite brilliant greenwash with a lime base. I too am going to bow away from this.

Is it acceptable to use Ordinary Portland Cement [OPC]?

biffvernon — Thu, 05 Jun 2008 08:13:52 +0100

Thank you. OPC is faster than lime. That's it.

Is it acceptable to use Ordinary Portland Cement [OPC]?

jon — Tue, 05 Aug 2008 14:00:58 +0100

Mike

"That's not fair Jon - it's a buy only one"

It seems that the Institution of Structural Engineers have partially released the text as google has captured it: You can find a captured version of the google capture at:

http://www.envisager.com/one/common/SE9_ethics_fea_Layout.pdf

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Fri, 08 Aug 2008 21:49:36 +0100

Thanks Jon, Will have a look at that.

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Sat, 22 Nov 2008 20:56:17 +0000

Lots of you not voted on the Ordinary Poortland Cement [OPC] poll yet.We're at 97 votes and it would be great to get to 100 [or even more] so thet we get representative sample

Is it acceptable to use Ordinary Portland Cement [OPC]?

rumi_ecobuilder — Thu, 08 Jan 2009 00:52:37 +0000

I think like many high CO2 emitting building materials OPC has its place, and where possible, and within budget constraints alternatives should be used if possible.

The post, post modern eco-age is going to be, I beleive one of a mix of new technologies and compromise unless there is enough pressure to pursuade governments to legislate against the vested interests of the giants of the construction materials manufacturing industry.

OPC however is one of the worst of all CO2 emitters, or as a colleague of mine states "with portland cement you get the double whammy on emissions, 1st from theenergy required to extract and process it and then from the CO2 relased by the clay in the manufacturing process". What sadens and worries me most is the deep conservtism of the building industry and the resistance to change I have encountered. OPC is the tip of a very large iceberg of ignorance, emissions in the construction industry does not stop at the materials and wastage but goes deep into the luxury lifestyles and SUV vehicle builders seem to favour as symbols of their commercial success.

Perhaps from this recession will emerg a better educated environmentally conscious and aware building industry ready to embrace rather than resist the new legislation that lies in wait for it in 2016.

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Thu, 08 Jan 2009 08:37:49 +0000

Posted By: rumi_ecobuilderOPC is the tip of a very large iceberg of ignorance,

Not sure its all about ignorance. I have colleagues who have been trying to find a replacment for OPC [both partial and full] for many years.

Please don't all shout Lime is the alternative, though I accept it is for some applications.

Is it acceptable to use Ordinary Portland Cement [OPC]?

biffvernon — Thu, 08 Jan 2009 12:43:49 +0000

LIME

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Thu, 08 Jan 2009 12:53:06 +0000

lol

Is it acceptable to use Ordinary Portland Cement [OPC]?

Nut Hatch — Fri, 09 Jan 2009 13:34:27 +0000

The discussion, earlier in this thread, regarding the reabsorption of CO2 by lime and cement is RED HERRING and completely irrelevant - the CO2 emitted in the extraction processes, the heating and finally the transportation far exceeds any reabsortion.

Is it acceptable to use Ordinary Portland Cement [OPC]?

jules — Fri, 09 Jan 2009 14:04:23 +0000

Maybe the answer is a new kind of cement... (sorry I don't know how to insert links)
http://www.geopolymer.org/science/cements-concretes-toxic-wastes-global-warming

Is it acceptable to use Ordinary Portland Cement [OPC]?

Mike George — Fri, 09 Jan 2009 16:14:46 +0000

Just select the 'text' option below the typing window

http://www.geopolymer.org/science/cements-concretes-toxic-wastes-global-warming

Is it acceptable to use Ordinary Portland Cement [OPC]?

jon — Fri, 09 Jan 2009 20:00:58 +0000

"The discussion, earlier in this thread, regarding the reabsorption of CO2 by lime and cement is RED HERRING and completely irrelevant - the CO2 emitted in the extraction processes, the heating and finally the transportation far exceeds any reabsortion. "

Doesn't stop it being cited ad infinitum though