# Bagged premixed lime mortar for tuckpointing



## dom-mas

stuart45 said:


> You can't get Feebly, Moderately or Eminently hydraulic lime as a putty as it will go hard in water.
> Nowadays it's called NHL 2, NHL 3.5 and NHL 5. I see that Virginialimeworks stocks it.
> Normally we use 3.5 for external work or 5.0 for chimneys or other really exposed areas. 2 is for really sheltered or inside.
> The latest info on lime mortar is that cement shouldn't be added if possible as it reduces it's ability to breathe and can separate from the lime over the years. However lime can be added to a cement mortar such as a 1/1/6 gauge.


That makes sense about the hydraulic limes only coming in bags

What is the difference though in using a bit of portland as opposed to a hydraulic lime. Portland is still burnt limestone with an alumina and silica content. Basically using an impure limestone. From my understanding Portland is essentially the most hydraulic of the limes. Haven't done any real looking into it, that's just my understanding.


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## stuart45

I'll have to have a look on the net later to see if I can find you any info. For years a bit of portland was used with pure lime, but the latest info from the Building Research Establishment here suggests that the lime with OPC doesn't breathe as well as even 5.0 NHL which is the hardest of the limes, even with only a small amount of OPC.


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## dom-mas

If you could find a link that would be great. I'm not very good at searching the web


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## stuart45

http://www.buildingconservation.com/articles//cement/cement.htm
Here's one I found


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## dom-mas

that's interesting. As little as 5% can be a problem. That's tough, Can't find hydraulic limes readily available here, nor brick dust. And I don't have the time or desire to make any. Something I'm going to have to think about next restoration job


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## rogerhattman

Dom-mas:

Air entrained autoclave is another name for type SA. So, that is a type S.

Cement + lime does not equal hydraulic lime.

Grey cement has four phases:
alite, belite, celite, ferrite. Alite and belite are most of it. Alites set fast, while belites are the slow setting part. NHL is all belite.


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## TheItalian204

I actually used Spec-Mix Lime and Sand Type S today...comes in blue Spec-Mix bag with red tag..not bad but would not use on big jobs.


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## dom-mas

what's NHL? Normal hydrated lime?

While I know that Lime + Portland doesn't = hydraulic lime it is like taking a white flour, adding wheat germ and fiber or whatever and calling it wholewheat flour (only analogy I can think of right now I'll think of a better one after I log out) Same ingredients just put together right before mixing rather than in the rock millions of years ago. I never would have thought that the portland would migrate after the set and seal the lime. I know that lime migrates a bit but never would have thought the Portland would. Or maybe it does it before the full set has occured. I'll have to re-read that article.


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## wazez

Ok guys I'm trying to let this soak all in.:clap:

Thanks for all the replys up to now.................


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## dom-mas

Ok re-read the article and I guess the portland migrates during the set. That makes way more sense. Oh boy on the look out for damned brick dust.

Any one kow the ratio needed? I used it once just for fun on a small job where I was just replacing a dozen or so bricks. I can't remember how much I used and don't know whether it was even a decent mix since the house was torn down a year after I did the repair (redevelopment)


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## Tscarborough

I save the sludge when I am cutting brick. I have 3 5gl buckets full of brick dust to use in lime plaster, 2 red and 1 yellow.


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## stuart45

dom-mas said:


> what's NHL? Normal hydrated lime?
> 
> .


Close. 
Natural Hydraulic Lime.


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## rogerhattman

As an alternative to brick dust, try metakaolin. Concrete Supply places should have some.


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## TheItalian204

rogerhattman said:


> As an alternative to brick dust, try metakaolin. Concrete Supply places should have some.


speaking of mixes...whats your fave mix not involving fiber?(stucco)


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## rogerhattman

Even though I have a bag sitting here, I have not used it. I am waiting until I need to do a white stucco. Generally I like NHL 2 unless the area is exposed. I vary aggregates alot:marble, granite, and of course sand.


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## dom-mas

It's interesting that the NHL 5.5 contains up to 30% clay and only comes up with a comp strength of 800psi, yet OPC contains as little as 33% clay and yields a comp strength of over 2000psi.


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## Rock Headed

Way I always understood it, you can make "lime putty" from bagged hydrated lime....but that it was not quite the same as true lime putty. Meaning, that if I open a bag or more, fill a barrel or a buckets with the powder, add water and mix, leave sit overnite or over a week with standing water cover the lime mix, that it will not truly have the *quite* same preoperties as traditional lime putty.

Strengthe will be even less than the true historic mortars....


I'd love to be prooven wrong though!


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## TheItalian204

rogerhattman said:


> Even though I have a bag sitting here, I have not used it. I am waiting until I need to do a white stucco. Generally I like NHL 2 unless the area is exposed. I vary aggregates alot:marble, granite, and of course sand.


You are obviously talking about a little more complex stucco mixes...

However I have to admit only time I tried course sand(other two worked out successfully) mix I failed miserably...

Thankfully it was obviously not customer's house.


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## dom-mas

When they make bagged lime, the crush and burn pure calcium carbonate, CaCo3. they then run it through a a conveyor belt with steam or a water mist hitting it. This makes the powder go off some but not all, enough so that it's not volatile anymore at least and its still a powdered form. When they make putty, they take chunks of CaCo3, burn it then throw it in water. Extremely violent reaction (hydration) occurs. After it cools the lumps are putty. So no it won't be exactly the same but it will be extremely close and since most of the hydration hasn't occured yet when it's in the bag it should still have lots of setting to do in the wall. 

But I'm no chemist either so don't take my word on it.

Italian, he said "of course" sand. Not coarse sand. hahahaha.


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## TheItalian204

dom-mas said:


> Italian, he said "of course" sand. Not coarse sand. hahahaha.


I just realise that...i am like wtf...:laughing:

When I was doing stucco alchemistry in basement that particular one would NEVER work out lol :laughing:


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## dom-mas

Tscarborough said:


> My take was not to use hydraulic limes any more than to use portland as a gauging agent. This is the exact takeaway from the discussion so far as I see it:
> 
> For Heritage tuckpointing, the best possible mortar is a high calcium mortar with minimal silacious or pozzolan gauging materials, and a coarser graded aggregate with minimal fines.
> 
> I do not think that is the best mortar for new construction, or even for repairs of recent (less than 100 year old) construction.


From my reading yesterday, the only mixes that were really deemed not great were lime mixes with Portland at less than 25%. For whatever reason at that point the mortars gained LESS comp strength than a straight fat lime mix that was properly constructed. Permeability, comp strength, and flexural strength were all still acceptable (some higher some lower) with hydraulic mixes and mixes that were gauged with either brick dust or a pozzolan. 

It did seem that the higher the temp that the gauging material needed to be fired at the worse the performance. It seemed that this was because C3S was formed at high temps while C2S is formed at firing temps below 1000*C. Portland is fired around 1200*C if I remember correctly. I don't understand the science behind why the C2S is favorable to C3S but it was across the board.

The only problems with gauged materials that I really read about was when they were too hard for either the surrounding material or for the original mortar. Remember, masons have been gauging lime since the Roman era. i believe Pozzolans were "discovered" when the Emperor Claudius wanted the harbour at Ostia to have a break. In significant restoration the desire is to use a mortar that is reasonably water tight, yet permeable, wont damage the units and that later removal wouldn't damage the units either. Compatibility is key an in the past it would have been rare to use a totally no hydraulic lime since most all limestones contain impurities.

Sorry, long boring posts


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## Tscarborough

Actually, the problem with portland gauged mortars was that the portland inhibited the carbonation of the lime while not being present in sufficient quantities to provide an acceptable degree of hydraulic action alone, thus producing an uncured (and uncurable) mortar.


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## dom-mas

Tscarborough said:


> Actually, the problem with portland gauged mortars was that the portland inhibited the carbonation of the lime while not being present in sufficient quantities to provide an acceptable degree of hydraulic action alone, thus producing an uncured (and uncurable) mortar.


Right which occured in mixes variously reported as having portland contents lower than 1:1:6, 1:2:9, and 1:3:12 depending study.


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## puppys

What 5 pages of 'ideas' of how to match a stupid motar.?
How the heck (ll) did an account get anyone involved with this.?
Give me a break.
Any (ANY) mason would and could have this already written down on paper if not in his mind. We 'do' after-all play with our wares.
5 forum pages. No wonder folks question us.


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## Tscarborough

The Original question was answered within 4 posts, but it became a discussion on lime mortars. Have a lot of experience with those?


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## puppys

Tscarborough said:


> The Original question was answered within 4 posts, but it became a discussion on lime mortars. Have a lot of experience with those?


Sorry, I did not realized the question was answered. I did not read all the posts.

Without dout, if a man desires a motar to match, it'd be done. But, who does it...? You the agency, organization, public/private owner or do you the so-called mason they happen to call.?
You have an apartment, basement, garage, shed.....Are you a mason or just wanna be. Experiment all you can. Make it a hobby. Make it your life.
What..?, NFL knowledge is gonna feed your family.......


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## Tscarborough

The original question and pretty much nothing discussed in this thread had anything to do with matching mortar. You either misunderstood or answered the wrong post.


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## puppys

Tscarborough said:


> The original question and pretty much nothing discussed in this thread had anything to do with matching mortar. You either misunderstood or answered the wrong post.


Sorry


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## dakzaag

Tscarborough said:


> The original question and pretty much nothing discussed in this thread had anything to do with matching mortar. You either misunderstood or answered the wrong post.


Nicely done, I was lighting the torch...:jester:


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## Tscarborough

<Shrug> no need to fire off. In my experience, typical line masons don't know or care dick about mortar other than if it will stick to their trowel. They can't match, much less design an appropriate mortar, and the reality is that they don't need to. The Masons on this board are not typical line masons and can and should be able to design an appropriate mortar and match existing for repair, and understand the reasons why. 

In addition, they should advocate for correct and appropriate mortar design at every opportunity, even when it is not technically in their contract. They will be held responsible, and blindly following an inappropriate specification without a paper trail detailing why the specification is wrong will end up biting them in the ass.


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## dom-mas

rogerhattman said:


> fjn:
> BASF has a product Metamax (http://www2.basf.us/functional_polymers/kaolin/products/metamax/) that is a metakaolin. I would suggest contacting them to find a distributor in your area.
> 
> I have used old brick dust, which is really the same thing. Dust from new bricks I would expect to be a little different.
> 
> I would say try 10% of the mix or less. That should be plenty hard for most applications. You should compare various mixes with NHLs.


How much did the brick dust colour your mix? 

It seems that the temperature that additives are fired at made a huge difference in their properties. I'm not certain but I'm fairly confident that new brick are fired at a much higher temp making their dust quite different from an older brick dust.


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## puppys

Tscarborough said:


> <Shrug> no need to fire off.


And therefore you will train/teach every employee, general and customer.
Otherwise......


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## stonecutter

puppys said:


> What 5 pages of 'ideas' of how to match a stupid motar.?
> How the heck (ll) did an account get anyone involved with this.?
> Give me a break.
> Any (ANY) mason would and could have this already written down on paper if not in his mind. We 'do' after-all play with our wares.
> 5 forum pages. No wonder folks question us.


Welcome to contractor talk.


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## Tscarborough

I attempt to educate engineers, architects, and capital letter Masons. Small letter line masons do not need to know the technicalities, they need to know how to put units in the wall.

In most construction fields there are discrete, measurable standards for the materials and processes used, in unit masonry not so much. Combine that with most traditional higher education for engineers and architects focused on concrete with no distinction between it and mortar, and it is an uphill battle.

Over the last 20 years, I like to think I have made some difference, at least the frequency of my calls to defend C-270 on the jobsite have dropped considerably in this area.


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## rogerhattman

Definitely visibly, which is why it will not work for light colors. I would still call it a pastel though.

"It seems that the temperature that additives are fired at made a huge difference in their properties."
I agree.

I think modern bricks are not only fired at higher temperatures, but are comprised of different materials (deeper clays and shales). With that, you may well be getting something entirely different than old brick dust.

I like to think that metakaolin is close to old bricks, since it is clay that has been heated, to what I assume is less than 900C. This should be less than the kiln temperature used to make NHL. I cannot find firing temperatures so I cannot positively verify this. The alternative is NHL from purely siliceous limestone, since this has only one phase, belite. St Astier is purely siliceous. I am not sure of others. 
Kaolin itself, also seems to provide a bit of a hydraulic set


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## dom-mas

rogerhattman said:


> Definitely visibly, which is why it will not work for light colors. I would still call it a pastel though.
> 
> "
> I like to think that metakaolin is close to old bricks, since it is clay that has been heated, to what I assume is less than 900C. This should be less than the kiln temperature used to make NHL. I cannot find firing temperatures so I cannot positively verify this. The alternative is NHL from purely siliceous limestone, since this has only one phase, belite. St Astier is purely siliceous. I am not sure of others.
> Kaolin itself, also seems to provide a bit of a hydraulic set


The colour makes it tough to use the brick dust, unless you could find it from a buff coloured brick. Unlikely.

This metakaolin sounds interesting. 1000*C seemed to be the point that C3S was developed rather than C2S.

At what proportion to the lime would give a compressive strength in and around 400psi? NHL is pretty much unavailable here and i don't do near enough resto to bring it in myself, but if I could get a few dozen bags of this metakaolin it may do me for a while. I'm assuming it doesn't go off on it's own from moisture? It requires the CaOH in order to become reactive? Any change in the mixes appearance using it?


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## Tscarborough

In the old bricks, as a rule, the buff colored bricks were fired to a higher temp than the salmons, although both were low by modern kiln temps. The same holds true for modern wood/coal fired bricks like those made on the Mexican border. I am not clear exactly on the desired chemical makeup of the gauging material yet, but I am still reading.


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## dom-mas

Well salmon bricks are just bricks that are too far from the fire to get decent heat. Buff bricks are from white/grey clay.

The different chemicals desired are various, but involve alumina, silica and magnesium as well as the calcium, carbon, oxygen and hydrogen. There seem to be dozens of possibilities and obviously there are very complex interactions. The only chemical that I read about that was undesireable was the C3S, but I have no idea why. Chemistry for me was a long time ago and I didn't do all that well in it anyway.


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## Tscarborough

In modern brick making they use different clay bodies for buff and red bricks (or at least add minerals). In old brick firing methods, they were produced from the same clay body, and the only difference was the firing temps in the kiln or clamp.


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## dom-mas

Tscarborough said:


> In modern brick making they use different clay bodies for buff and red bricks (or at least add minerals). In old brick firing methods, they were produced from the same clay body, and the only difference was the firing temps.


Not to my knowledge. There are 2 different Clays. a red/orange clay, and a grey/buff clay. The grey/buff bricks contain little to no iron oxides (why they aren't red) which is why they are also used for fire brick


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## Tscarborough

I see, well I have done some lime mixes with buff and red brick dust and it definitely affects the color. The red makes a pastel pink and the buff gives an ivory, just as you would expect. Which one is better for the mix, I do not know. The pink sample has been hanging on my fence for 5+ years though, and while hard can still be scratched with a fingernail, although it does not dust. The ivory sample I can't find, so it was probably trashed years ago.


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## fjn

*mortar*

I have away for a week, this discussion is real interesting. I started burning brick as a hobby a couple years ago. I use a scove klin or clamp as it was called in COLONIAL WILLIAMSBURG. Used coal,soft & hard,along with oak,hickory and ash for fuel. Tried several clay deposits,the color of clay does not effect final color.Have used blue/gray clay along with tan clays. If any of you guys are interested a free book can be read called 60 YRS.A BRICKMAKER by A guy called CRARY. HE was born in i believe 1814 & wrote the book in the 1890s very fon read. Or type in WILDCATBRICKCO he has a link to that book it is free & complete on computer. I have to admit my computer skills are the closest thing to non existent or i would show pictures.


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## rogerhattman

I think this is what you are speaking of:
http://books.google.com/books?id=mB...ce=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

I just started it; it looks interesting.


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## Tscarborough

Here is some lime plaster with a red brick gauge, probably about 10%. Made with type S bagged lime, slaked in a bucket for a couple of days. it has been hanging on my fence for at least 5 years.


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## fjn

*books*

rogerhattman; That is exactly the book i was talking about. Thank you for the help putting the info. on this post. I"am clueless about how to do that. Thanks again.


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## mapple

*To sum it all up*

Gentlemen,

After reading the smeaton project findings and following your discussion - I will be parging a stone and mortar basement (circa 1914) soon. I planned to use either a type N or a homemade type O (no one seems to sell a premade one) by adding 1 part type S hyrdrated lime by volume to the off the shelf Type N cement mortar and of course sand. Since I am working on the inside on a natural stone (appears to be limestone) I am not concerned with excessive compressive strength, and since the existing mortar is in relatively good shape (i.e., not a repointing job), will not be exposed to the elements or any freeze-thaw action, my primary concern is vapour permeance and then durability. 

Will a type N (1:1:6) or type 0 (1:2:9) (c:l:s) mortar have enough permeance to avoid the often discussed problem of trapping water in the wall?

The other side of the wall is (unseen) but likely not dampproofed.

Thanks in advance for any help.

I have talked to a couple masons on different sites and they look at me like I have two heads when I mention lime mortar; both have recommended type s with an admixture to increase adhesion. Is it possible that given the sheltered relatively good shape, that something more durable like a portland sand mortar would be good enough?

sorry for all the questions


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## rogerhattman

Why use OPC at all? I parged my cellar with masons lime and sand close to 10 years ago. No problems with it. Since you have such a soft stone, you have no need for hardness. I have even used masons/lime sand on the exterior for pointing and have had no durability issues.


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## mapple

I only considered using OPC for the time saving aspect and the (perhaps false) assumption it will be more durable; i can't find lime putty anywhere - only hydrated lime. Can I mix the hydrated lime with sand and water on the spot or do I need to make a putty first?


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## dom-mas

You can use the hydrated lime just fine. It will hydrate once it gets water. I agree with Rogerhattman, it's indoors so really you can treat it like plaster, which was just a rich lime mortar occasionally with some fibers added


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## Tscarborough

If you are worried about chalking, i.e. rubbing up against it and getting a mark on your clothes, then you should use putty and gauge it. Otherwise, no need to even make putty from the Type S lime, just use it with sand and be done.


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## timp

Has there been any resolution to the best historic lime pointing mortars? Is it still deemed safe/ best to use a 1:1:6 Portland:lime:sand mortar for an old outdoor (cold-climate) limestone foundation for example? What is the observed lifespan of such pointing jobs in a freeze-thaw climate if done properly?

I've played around with some ordinary hydrated type S bagged lime with sand mortar (no OPC) and it really spread with trowel nicely, but it looked and felt like soft toothpaste even hours after I applied it.

Of course mixing up the terms "hydraulic" and "hydrated" seems to be a common problem for everyone but those in the lime business.

Since hydraulic lime is made by super-heating in a kiln to combine the ingredients CaO and SiO2 into calcium silicates at the high temperatures then I think it would be more comparable to Portland, and would be a very different product than could be had by taking ordinary hydrated type S lime and mixing it with a pollozan (without being cooked together at the high temperatures).

It seems to me that it's not so important as to whether a hydraulic lime is natural (naturally occuring NHL) as it is important that the ingredients CaO and SiO2 are proportioned and mixed together before they are kiln cooked together to chemically combine as opposed to mixing the CaO and silicas at normal room temperature where they are not chemically combined.

I've studied that bagged hydrated type S lime based mortar is suitable only for indoor use or protected outdoor use with very low compressive strength. Hydrated type S lime based mortar with added pollozans is a bit faster setting and harder, but still questionable for outdoor use. NHL (various ratings) hydraulic based mortars are fully safe for exposed environments but are much more expensive $. And, 1:1:6 OPC:hydrated-lime:sand mortar is a common compromise here in the USA for older pointing of stones and brick. 

I've seen that virginialimeworks.com has a product Building Lime 200 that is described as composed of hydrated lime and pollozans to create a hydraulic lime just like "the ancient Romans" used. I'm skeptical if it is just hydrated type S mixed cold with a pollozan (ingredients not kiln cooked together). That could be a great money-making scheme because of how low cost type S lime is available. You could make it yourself cheap. Would this mortar really be quality compared to kiln cooked hydraulic lime that costs much much more $$ money?

That seems to be what I've studied so far. Does this seem to be accurate?


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## dom-mas

I don't think it is accurate. You are saying that an NHL would be more like OPC than Regular lime mixed with Pozzolans but the research has shown that NHLs and Lime mixed with Pozzolans or brick dust react more similarly.

If you are using 1:1:6 as an historic re-point mix you are using a type N mix which would never fly in any true restoration I have been a part of, below grade would be a possible exception.

I do agree that it most likely makes little difference whether the NHL is natural or is formed by burning the silicate and the calcium carbonate together. 

No comment on Virginia Limeworks since I have no experience with them

Oh and as for the BEST mix...each situation is different and requires it's own mix


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## timp

Dom

What is the current ratio of OPC:lime that you can not go less than (on the OPC) because the mortar starts getting weaker and less compressive strength?

Does this rule out Type O and Type K mortars? Or, are they reasonably strong and lasting and do not separate? I know that the studies have shown that a 10% addition of OPC to hydrated lime mortar only makes it weaker than the ordinary lime mortar. But, what is the percentage of OPC addition where the lime mortar gets stronger from the OPC addition (because the OPC strength takes over)?

Also, who sells good China Clay around here? HJ Mohr in Oak Park, IL has bags of private label China Clay for $21.00 per bag with no markings or description of contents.

US Heritage Group in Chicago advertises NHL 3.5 hydraulic lime for about $44.00 per bag. Other than these I don't see much advertised in the lime mortar department here near Chicago, IL.

Of the three choices...
1) Hydrated (cheap!) lime and china clay w. sand
2) NHL 3.5 and sand
3) hand mixed Type O hydrated lime and OPC w. sand

..what would you feel most durable and best method for an older limestone foundation of a house?

Thanks,
Tim


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## dom-mas

timp said:


> Dom
> 
> What is the current ratio of OPC:lime that you can not go less than (on the OPC) because the mortar starts getting weaker and less compressive strength?
> 
> Does this rule out Type O and Type K mortars? Or, are they reasonably strong and lasting and do not separate? I know that the studies have shown that a 10% addition of OPC to hydrated lime mortar only makes it weaker than the ordinary lime mortar. But, what is the percentage of OPC addition where the lime mortar gets stronger from the OPC addition (because the OPC strength takes over)?
> 
> Also, who sells good China Clay around here? HJ Mohr in Oak Park, IL has bags of private label China Clay for $21.00 per bag with no markings or description of contents.
> 
> US Heritage Group in Chicago advertises NHL 3.5 hydraulic lime for about $44.00 per bag. Other than these I don't see much advertised in the lime mortar department here near Chicago, IL.
> 
> Of the three choices...
> 1) Hydrated (cheap!) lime and china clay w. sand
> 2) NHL 3.5 and sand
> 3) hand mixed Type O hydrated lime and OPC w. sand
> 
> ..what would you feel most durable and best method for an older limestone foundation of a house?
> 
> Thanks,
> Tim


Well I don't really think that there has been a consensus. The smeaton project basically says don't use less than a 1:1 ratio of lime to Portland, but they do suggest using NHLs, pozollans and brick dust.

When you ask about type O an K it is an impossible question because you aren't saying how you are creating that mix. I know I've seen type O mixes made with OPC rather than pozzolans that have lasted 20 years (not work I've done) however research has shown in other circumstances that it doesn't last and that the Portland and lime separate. 

I don't have an answer to any of these questions really, except that use of an NHL or using Pozzolans hasn't resulted in any problems. My problem is that neither of those are available to me at all.

Oh and in my opinion, i think a 1:1: 6 or maybe a 1:1:5 would be a suitable below grade mix.


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## timp

Who distributes Metastar or similar in Chicago area? I only know HJ Mohr materials in Oak Park, IL has an unbranded china clay for sale at about $21.00 a bag.

Thanks


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## fjn

dom-mas said:


> Well I don't really think that there has been a consensus. The smeaton project basically says don't use less than a 1:1 ratio of lime to Portland, but they do suggest using NHLs, pozollans and brick dust.
> 
> 
> 
> 
> 
> There has been so much discussion about the ratios however,i believe it was in the book Building With Lime by Michael Wingate that the ratio was stated. I know in his book he said the opc should NOT be less than 50% of the lime


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## dom-mas

fjn said:


> dom-mas said:
> 
> 
> 
> There has been so much discussion about the ratios however,i believe it was in the book Building With Lime by Michael Wingate that the ratio was stated. I know in his book he said the opc should NOT be less than 50% of the lime
> 
> 
> 
> Right but there have been other books that advise using OPC as an additive of 1/4-2/5 of the cementicious materials. Seeing how the back to lime movement is only what? 30 years old or so which is negligble to the life of a masonry structure (hopefully) all the research is mildly suspect. Remember how doctors were saying that eggs were evil 25 years ago, now they're saying their one of the healthiest proteins to eat.
> 
> I guess what I'm saying is that unless you're making a mix exactly how it was made for that building 100, 200, 300 years ago, only our children and grandchildren will know whether we made the right choices.
> 
> Therefore, in my opinion, the use of straight lime, natural NHLs of the proper comp strength and occasionally lime with fly ash or other pozzolans are about foolproof. I on the other hand do continue to use OPC as an additive because really I have no other choice, and i would rather put in a soft mix that doesn't last rather than a type N in most situations.
Click to expand...


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## fjn

dom-mas said:


> fjn said:
> 
> 
> 
> Right but there have been other books that advise using OPC as an additive of 1/4-2/5 of the cementicious materials. Seeing how the back to lime movement is only what? 30 years old or so which is negligble to the life of a masonry structure (hopefully) all the research is mildly suspect. Remember how doctors were saying that eggs were evil 25 years ago, now they're saying their one of the healthiest proteins to eat.
> 
> I guess what I'm saying is that unless you're making a mix exactly how it was made for that building 100, 200, 300 years ago, only our children and grandchildren will know whether we made the right choices.
> 
> Therefore, in my opinion, the use of straight lime, natural NHLs of the proper comp strength and occasionally lime with fly ash or other pozzolans are about foolproof. I on the other hand do continue to use OPC as an additive because really I have no other choice, and i would rather put in a soft mix that doesn't last rather than a type N in most situations.
> 
> 
> 
> That is a good rule of thumb,it is like the first rule of medicine,DO NO HARM.:thumbsup:
Click to expand...


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## fjn

timp said:


> Who distributes Metastar or similar in Chicago area? I only know HJ Mohr materials in Oak Park, IL has an unbranded china clay for sale at about $21.00 a bag.
> 
> Thanks


 METASTAR dist. FITZ CHEM CORP. Itasca Illinois (630) 467-8383 ask for Terri Gates


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## timp

dom-mas said:


> There has been so much discussion about the ratios however,i believe it was in the book Building With Lime by Michael Wingate that the ratio was stated. I know in his book he said the opc should NOT be less than 50% of the lime


 
Mortar mixtures of Portland-Lime compositions of Types M, S, N and O are all composed of ratios having Portland being at least 50% or more of the lime content. Only type K would have a Portland content of less than 50% assuming by volume to the lime. Type O would have the 50% Portland to Lime composition of 1:2:9 Portland:Lime:Sand. This is assuming you mixed it yourself with actual Portland and Hydrated Lime as opposed to buying a mason premix which would actually likely contain Ground Limestone instead of Lime. Even Brixment is made with ground Portland and ground Limestone which is not reactive like Hydrated Lime.

So, M, S, N, O mortars look like they are within that theorized limit of requiring a Portland content of equal or greater than 50% of hydrated Lime content limit to be of sound quality. *edited

But, as mentioned if you really are preserving a softer stone building then you may as well go with the NHL Hydraulic lime, or the Hydrated Lime+calcined metakaolin mixtures because the M, S, N, O mortars are relying on Portland as their primary binder and Hydrated Lime as a plastic workability sticky agent -- which makes them unyielding and less porous.

And, it is important to note that most premixed mason cements and mortars do not even utilize hydrated lime. If you can find the spec sheets for alot of premixed products they are using ground limestone as the "lime" in the mix. I don't actually know which qualities of ground limestone are similar to actual hydrated lime other than making the mortar more plastic. 

An interesting note is that some of the Portland-Lime studies I've seen tested the hydrated Lime mortars using a putty and having a Portland content listed as 10% of the WEIGHT of the Lime cement...and resulted in that strength decrease compared to an ordinary Lime putty mortar. A 10% WEIGHt of metakaolin increased the lime mortar strength. But, when we start comparing weights vs volumes it get's confusing. A 10% of weight of a lime putty can be a lot of volume.*

source of this study:
The Use of traditional Limes For Lime Mortars by Violeta Bokan Bosiljkov, Slovania 2001


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