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Suggestions for which lime in chinking

Started by DonW, February 22, 2021, 11:09:36 PM

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DonW

I'd really like to try my hand at quicklime. Is it appropriate in this use?
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Don P

Sure but you would want to slake it first,
Quicklime + water = slack lime (slaked lime) + major heat

This was done often before my time but Dad remembers the plasterers coming to the job early in the construction process and mixing quicklime and water in the back yard. Then coming back periodically to stir it, the longer it slaked the better the lime putty got.

Slack lime is available as masons lime, or hydrated lime. I think this is done with steam and is barely slaked to make a less reactive powder rather than a lime putty.

Quicklime is made by burning limestone, marble or shells in a lime kiln to drive off the CO2 from the calcium carbonate.

As lime "cures" over many years it absorbs CO2 from the air to return to calcium carbonate.

Be very careful playing with quicklime, it can blind you, scald your lungs or burn skin, it is the reactive "hot" form of lime.

Don P

Which brought to mind, I worked for the son of a plasterer, well multiple times over the years. We were talking about the old school plasterers one time and he explained how they would check the weather conditions, temp and humidity, and "gauge" the plaster with gypsum to adjust the setting time. That was for interior work. I have no experience but I think with exterior it was gauged with clay.

After doing blockwork at the job today I went over to the old mill to meet with the the owner and mill guru. We were looking at the lime mortar and handmade bricks on the old springhouse on our way out. It was obvious the lime was locally made. You can see bits of unburned limestone grit in the mortar. I think I have a pic of some of that kind of mortar in my gallery...

Yup, here we go, the white flecks in the mortar are bits of unburned rock. In modern lime or even back then for finer plaster work that is screened out. This was really crude stuff in a rock chimney. The chimney and rock around there is all dolomitic limestone which I believe makes less than ideal quicklime but every form has its positives and negatives depending on use. Quite a bit of lore and science around such a simple seeming compound



DonW

In my dreams only could I replicate the old lime mortars. Having chipped many bricks clean the nature of this old lime is a wonder to me. Even with the imperfections, (or because of) from processing - unburnt shell shard, bits of charcoal and so on and so on.... Still I prefer even my version using slaked lime a hundred times over Portland cement based mortar which I've not used for years. Quicklime though I have not been able to find until now. My impression, even from what you write is that in this form it can be stored up a bit longer waiting to use. I end up tossing the slaked flour in sacks after about six months because I don't trust is after that.

Thanks for mentioning taking precautions. Once I've got my load my plan is to mix it as dry as possible to avoid splattering. It's also interesting seeing it mixed in with clay even though I'm after a light version for the chinking. Clay and lime, what a great combination. I've used one atop the other but not mixed together. 
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Tom King

It's actually pretty easy to make lime mortar, or plaster, and you don't even have to burn limestone, or sea shells.  The chemistry is really pretty simple.

Quicklime- CaO, is what you get when the CO2 is burned off of limestone-CaCO3.  It's very unstable, so you make it more stable by mixing it with some water, which makes Hydrated Lime- CaCOH.  Quicklime will make the water boil when they are mixed.

Long story short, just buy some fresh, hydrated lime.  Screen it into water, and let it sit for several weeks, or as long as possible. That makes Lime Putty.  Hydrated lime can be found in type N, and type S.  That's where the types of mortars get their names.  Type S has dolomite in it.  For mortar, or base coat, I like to mix the two types, but that's just a gut feeling, thinking it might be a bit more flexible, and it might not make a difference.

Dolomitic Hydrated Lime Type S | Graymont

Dolomitic Hydrated Lime Type N | Graymont

Lime Putty can be kept for years, covered in water in buckets with lids on them, much longer than, as you found, kept dry in bags.

You need to right kind of sand, which is kind of hard to find.  Since you'll be using Lime Putty, which always makes the final mix better working than simply buying mix in a bag, you need dry sand.

I find the perfect sand for Lime Mortar, or Lime Plaster base coat, comes in bags from Quickcrete, and Sackrete, called "Plaster Sand".  It costs about $250 for a pallet of it.  If your time costs nothing, you might be able to find something that will work, but since we're charging, it's just as cheap to buy it ready to go to work.

I saw some recently, sold in Home Depot, for setting pavers that looks pretty good.  It needs to be coarse enough that when you flex the bag, it doesn't just run like beach sand, but sticks together enough that when you bend the clear bag, that are crevasses all in it.  That sand was wet in the bag though, but I would buy some for small jobs, because the Plaster Sand is hard to get unless you buy a whole pallet, or at least, around here.

Organic material in the mix, like clay, will cause the final product to be weaker.  We have a house to work on now, built in 1798, where they just used the sandy dirt out of the yard, and it's the poorest quality old plaster I've ever seen.

None of the old recipes for Lime Mortar, that I have seen, call for any gauging.  George Washington wrote specifications for various buildings, calling for different ratios of lime to sand, but never for anything else.

I have a book for the early 20th Century, that has charts in it showing flexibility, adhesiveness, and other things, with various mixes, including Portland Cement.

If you've seen old plaster that looks like it has grown a white fur coat, that's the Gypsum in it.  Gypsum expands when it absorbs moisture.  For this reason, I cheat when gauging plaster, and use a little White Portland Cement.  You can't tell the difference with the finished product, but using such a small amount of Portland, according to the charts, it still remains flexible, breathes, and gives you several days to work with it, plus is now waterproof, and won't grow fur..

I first figured out the Portland Cement gauging when I plastered a room using US Gypsum Diamond, which is a great finish coat, but it has a grayish hue to it.  I called US Gypsum, and asked why it had the grayish hue.  They guy told me that was the Portland Cement in it.  A lightbulb lit, and I tried White Portland Cement.

Here's a picture of me making a small batch of Lime Putty, for a small plaster repair.  That's a kitchen sifter from Walmart.




Tom King

I should have included: 

 Hydrated Lime, that you buy in bags, is not fully hydrated, like it is in Lime Putty, but hydrated just enough to be stable in transport, and handling.  As you have seen, it will harden in the bag, just from absorbing CO2 from the air, and be on the way back to turning back into limestone.  That's why Lime Mortar, and Plaster become harder, and stronger over centuries.  It's always trying to turn back into Limestone.

DonW

This is helpful and'll take a few readings to get through my thick skull. All the same I have to say why this old mortar I've chipped away at hour after hour is so striking. Even after some hundreds of years, at the center of the brick it is still not brittle or crumbly but almost rubbery or elastic with good adhesive strength. My own mortars, while they harden and adhere just fine never come anything near to  that and it's hard for me to attribute this self-healing characteristic of lime to the results I get. Not so with the proper mortar, this plasticity - of course it's a completely inadequate description - is clearly, after so long, still in some kind of active state. An old man whose father was a bricklayer described the process once for my benefit. Two striking aspects were, use only river sand i.e., sand with sharp edges aka sharp sand, and the other was the process of letting the mortar "rot" that is to say early in the season the mason would go to the building site and, one way or that other one mix the lime and sand. Over the summer the mortar would sit covered, somehow, and in three months only then be ready for use. 
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

DonW

So the other thing was that I used to have access to what's called "well lime" which is lime in a sealed container saturated with water sunk to the bottom of the well or cistern and left there. The best quality used by plasterers is 40 years standing like that. I did my best when I filled a big bottle with fresh lime and water and put it under the crawl space in the workshop. Since then the house is sold and no sigh of my cellar lime in 25 years. 
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Don P

Under water, or in the middle of a wall CO2 can't get to the slack lime or lime putty to convert it back to stone.

One thing I've heard is the bagged hydrated, masons, lime will make lime putty but it isn't the same as starting from quicklime. As Tom said they added just enough moisture to stabilize it but it kind of kills it too. I'm just a carpenter and try to pay attention when the other trades are talking but take it with a grain of salt, that isn't the same as experience.

Then there's hydraulic lime, don't know nuthin bout that  :D

Tom King

There was a reason I said "fresh" hydrated lime.  You can tell the freshly made stuff, because it's very light, and fluffy.  There is much information on my favorite manufacturers website:   Graymont.

Places that sell it for water treatment always seem to have the freshest, that I have found.  I don't bother with hardware stores, unless it's sold there for water treatment.

The oldtimers didn't use Quicklime in the mix.  It's too unstable.  They first had to hydrate it by putting it in water, to make hydrated lime, but they didn't call it hydrated lime.  They just called it lime.

Lime mortar, and plaster changes over centuries, so anything we make, during our lifetimes, will not be the same as the old stuff we find, or at least, not as long as we're here.

I have some books on plastering printed in the first part of the 20th Century.  They were still using lime plaster then, and gypsum only took over because it was faster, and cheaper.  In that book, there are pictures of workers mixing lime putty in large vats, in anticipation of an upcoming job.  The vat looks to be about 30"x 6'x 3' deep.  They have a shaker screen on the top that they dumped bags of hydrated lime on, into the water in the vat.

I used to used premixed bagged stuff, when Virginia Lime Works was in business, but the stuff made from Lime Putty is Much better to work with.  I only started making it, and started reading about it, after they closed in 2012, if I'm remembering that correctly.

I doubt there's any difference in Lime Putty kept in a well, or like I do, in plastic 5 gallon buckets, with the snap-on lids.  There is enough water inside that it always stayed cover with water, so CO2 never touches it.

When we're using Lime Mortar, it can stay mixed up for weeks at the time.  In the mornings, it's stirred up in a wheelbarrow with a Mattock (called a grubbing hoe around here).  We use it so stiff that a mortar hoe won't do much to shake it up.

Hydraulic lime has something else in it, so it's not as pure as hydrated lime.  It's not produced in the USA any more.  I forget all the details about it, because it doesn't apply to what I do.

Don P


DonW

Quote from: Don P on February 24, 2021, 06:54:33 PM


Then there's hydraulic lime, don't know nuthin bout that  :D
Hydraulic, it will surprise nobody, hardens under water. The foundations of the old brick buildings, which extend below canal level in the center of Amsterdam are held together with hydraulic lime mortar as I understand it, for example.
My practice of storing lime at the bottom is precautionary and practicle. What else are you going to do with that unused space? Sorry but I believe there is some rational for the practice. In the case of the 40 years putty, apparently there is some added value. The lime under water is not only excluded from oxygen but as Tom says it it is regardless undergoing constant alteration, the structure improving by continually breaking down to a finer and finer grit. Probably it is the choice in making these elaborate ceilings -I don't know the technique, it is not my thing. I suppose an analogy could be the difference between basswood and boxwood to the wood carver boxwood having a finer, denser, or whatever, structure resulting in a more defined form.
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

DonW

Hjartum yxa, nothing less than breitbeil/bandhacke combo.

DonW

Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Tom King

It was really nice of Graymont to preserve that website.  I think it was 2012, when Virginia Lime Works went out of business.  They are/were a great bunch of people.  If they are back in business, I haven't heard anything about it, but I'd still be making what we use this way.  

I expect they purchased hydrated lime, to process into the things they sold, from Graymont, hence the connection.

Tom King

Quote from: DonW on February 24, 2021, 11:07:12 PM
Quote from: Don P on February 24, 2021, 08:07:16 PM
8), here we go;
Products and Services | Virginia Lime Works | Makers of Traditional Lime Products (graymont.com)


also called a mad-axe up here  :D
Are those perscription glasses for reading that minuscule print?
Like my website (pitiful in comparison), made long enough ago, when most people were using computers to read websites, instead of phones.

Don P

I'm still having to zoom and roll around the pages on a desktop screen, old eyes and fine print  :D Some good stuff there so far though, well worth the effort.

I saw this on using hydrated vs quicklime;

Quote. Lime putties that are run directly from quicklime are considered better when applications require superior plasticity
and carbonation. Also, as it is in a wet state there is a greatly reduced risk of the material carbonating while being stored. It can be argued that if
one adds water to hydrated lime it forms lime putty, but this is both true and misleading. Since the material has previously been slaked it is already
"hydrated" lime. When water is added it forms a lime paste. And although the particles of lime may absorb moisture and fatten, the continual process
of dissolution and precipitation does not occur. Basically this is just an extension of hydrated lime.

And an explanation of the mortar with bits in it I often see;

QuoteThe "hot mix" method of making lime mortar is a process that appears to have been used predominately for historic building construction. Taking the quicklime (also known as lump lime) fresh from the kiln and adding the sand and lime directly seems to provide
a mortar that tends to have more durability than that of "cold mixed" lime putty and sand. It is often advisable to repair structures built with hot lime mortars with hydraulic lime, as the properties of this material tend to perform like hot lime mixes (strength, durability). Also, the evidence of lime inclusions (small particles of lime distributed throughout the mortar) is indicative of a hot mixed mortar, whereas lime "smears" or "streaks" often can be attributed to improper mixing of lime putty mortars.
By using hot lime mortars for construction, the construction process could begin much earlier allowing the masons to get to work immediately while reserving and slaking lime in advance for plasterwork. Due to the potential for "air slaking" which may cause pitting and popping, hot lime mortars were not used for plasterwork.


kantuckid

Not that I know anything about plastering but this thread reminded me of my first adventure in wallpaper on plaster in the mid 1950's after we'd moved in with my Grandpa after my Grandma died too young. The house in Topeka, KS was one of the first built there after the railroads began operation on west and built by the first town doc.
 The plaster all contained horsehair as a binder which sort of got in our way as we made repairs under the layers of old papers we removed. I got the mess job of pulling off paper, hauling it off, kid work. 
That house was small and not a fancy mansion by any measure, but what a piece of art, carpentry wise! Had a solid walnut staircase all done by hand. On adult homesick runs in years past I'd drive by to see where I grew up and it was an obvious rental? crap hole, what a shame. Probably should have become a historical place. 
Kan=Kansas;tuck=Kentucky;kid=what I'm not

Tom King

Hair would have only been in the first layer, of the typical old three layer plaster system.

The more hair added, the wider can be the gaps between the lath strips.  The wider the gaps, the larger, and stronger the keys can be, but the hair has to be in it to keep the keys from just falling off.

It doesn't really matter what type of hair, but longer is better.  I did some small repairs in an 1850 house using Havanese hair saved by my Wife, who is a Havanese dog breeder.  That hair was pretty long, and silky soft.  I would use it all the time, if I could get enough of it.

Back in old times, they used everything, so when the horses shed out in Spring, they would save the hair, as I'm sure they did when they killed hogs, and saved the scraped off hair.  We have horses, but they wear blankets in Winter, so the hair they shed in Spring is too short to be worth bothering with.

I have also used human hair, saved by salons for me.  With enough hair in the mix, gaps between lath can be as wide as 3/8", and it makes big, fat keys.

I first learned of the name Graymont, as a lime manufacturer, seeing it on pallets in the room where Va. Lime Works mixed the stuff they sold in bags.  They make a really nice product.

I mix plaster, and mortar in a mortar mixer, but you can't add the hair into basecoat plaster in a mortar mixer, or it will just load up on the paddles.  We transfer the mix from the mortar mixer, to a pretty large old cement mixer, and the hair is fed into the big center opening as it's turning.  Adding the hair in takes the longest amount of time.  You can't just dump it all in at one time, but has to be lightly added with fingers.

This explains a bit more about the differences of lime putty made directly from quicklime, but I can say that almost no one does that now, and I'm not convinced that it makes enough difference to really matter, or at least, not enough to go to the time, effort, and expense of burning a lime rick.  http://www.buildinglime.org/Thomson_TypeS.pdf

DonW


I've spent many hours whacking horse hair atop the workbench with a bundle of sticks to separate and loosen it since the last thing you want in the plaster is a lump of hair and plaster. That plaster is really special stuff, though if used as a top layer you'll have furry walls. I'd use only particular hair though, (I've once used rain deer which is the best so far from the thick coat), horse, pig and so on and so on...all non-oily so the plaster adheres over the long-run. In Holland where I lived, many times the mason was also the butcher, which makes sense, bricklaying in the warmer months, butchering when it's to cold for using lime, never begin lime work outside after September. All the pig hair was saved for mortaring the tile layer at the peak of roofs.
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Tom King

There is a company in Ohio-Minetek, that sells Quicklime by the dump truck load.  I've never had a job that needed anything like that much lime, but if someone wanted to make a bunch of lime putty from quicklime, they could do it.  It would have to be used up pretty fast though.

Don P

DonW, you were mentioning wanting to play with quicklime, where is it coming from?

On hair, someone mentioned to me one time to be careful to wash up before eating or such if working with old hairy plaster, it sometimes came from the tannery and might have arsenic or other chemicals on it that isn't too good for the digestive system. To be honest I have that in mind whenever working on old buildings, who knows what is in the dust raining down on you. I pulled out a brown glass bottle today with something still in it, some of that stuff can make your babies be born naked  :D.

I was late to work this morning, got engrossed after thinking to check up on the nearby lime company, just ag lime but an interesting history, they are the oldest continuously operated mine in the country;
The Austinville Mine (arcgis.com)

DonW

The nearest I've come to locating a source is the kiln in Delta which is just the other side of the mesa from me. It's not clear if they are even processing quicklime there. From the website though they make it tempting to go over and try my hand. And the rest is same as Tom, by the dump truck load. Nearest by Greymont's outfit up in Salt Lake City. All industrial orientation, road stabilizer, water treatment, that kind of business.

Yesterday a chipping away, investigating the existing chinking situation and found what I imagine is a big flaw in the original light gray lime mortar. It is so dry and hot here, borderline desert really, that the free water gets drawn from the mortar far too quickly and it has no chance to bind. It means that in no time the structure is out of the mix and it quickly falls apart. I think in these conditions it is a difficult job to properly chink with lime. Doesn't mean I've given up by any means. Otherwise a plastered surface outside would be screened from light and wind with hessiean kept humid the first seven days. Doesn't seem practicle or effective on a log wall though.

I got a whole mountain behind me of potential quicklime, Chalk Mountain, up on the Hog Back. I've had no time yet for investigations + snow's blocking the road yet. Saturday's spent spying out some Old growth pines on Grand Mesa.

Funny thing you mentioning your find Don, today my daughter returns from our old dump site out the back with old bottles containing some awfully suspicious stuff. :-X
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Don P

  Ain't no telling what you'll find. On another job I was finding tons of mason jars and other glass. Come to find out the previous depression era owner was renowned for her 'shine  :D.

Between me and that mine I was mentioning is an old brick mansion. Alongside the road at the end of that property is what looks like a small old time iron furnace. I was told that it was a lime kiln. If so I'm guessing they were doing it the same way as iron, just without the ore, by layering limestone and charcoal and applying a blast?

In chasing Tom's links and then Graymont, it turns out dolomitic limestone is the desirable base of type S. The Romans, who were using dolostone, had a restriction that required lime to be slaked for a minimum of 3 years. Apparently the magnesium must be really slow to break down naturally. Graymont noted that in the autoclave hydration process they achieve the same thing by using high pressure to do the same thing quickly.
Dolomitic Hydrated Lime Type S | Graymont
I'm betting your mountain is hi cal, type N
Read that paper he posted a link to for more, I think you might be wanting the type S. Putting together the highly desirable Ohio Niagra formation dolomitic finishing plaster in the paper and the Niagra lime putty Graymont sells. ... and if you try to slake that on your own, its 3 years, I'm getting what Tom is driving at now.

It is making me want to try plastering the basement we're working on.


kantuckid

Wife cuts my hair and piles it around plants to keep the deer away-which works sometime...
Book I'm reading has ghetto thieves who are burglars and talking about stealing human hair wigs that are directional hair vs. thrown away hair-reminded me of this thread-sort of.  ;D
Kan=Kansas;tuck=Kentucky;kid=what I'm not

Tom King

The Type S sets up a lot faster than Type N.  It's still nothing like a concrete mix sets up.  

I'm not sure how much the bond between the logs, and mix is worth anyway.  Most of the old that I've seen is staying in there because of shape.

If you have plenty of time, I'd mix up some Type S, and see how it works at a sample place.  Make other samples with 10 percent, and 20 percent as much White Portland Cement, as there is lime in the mix, and see how they work.  With that small percentage of Portland, it will still breathe, and have some flexibility.

If that doesn't work, I'd try painting the mating surfaces of the logs, where the chinking will go, with Thompson's regular water seal, to keep the wood from sucking the water out.  That Thompson's is nothing but wax in mineral spirits.  The mineral spirits need to outgas away, leaving the wax.

If the lime mix still doesn't seem satisfactory, I'd try a thick layer of Surewall, at least for the outside surface.  I've built 5" thick bases for showers with it, and it doesn't crack that thick, even though it's intended for thin applications.  I have also used it for a barrier on old chimneys, that were plastered over with lime plaster.  All have held up well for years.  It has thick, stiff fibers in it, but you can slick finish the surface, even with all that fiber in it.

Here's another link, from my Favorites folder, that has some formulas for the different Portland mortars, but may be useful for ideas anyway.

https://www.lime.org/documents/publications/free_downloads/fact-masonry.pdf

DonW

Quote from: kantuckid on February 27, 2021, 07:16:33 AM
Wife cuts my hair and piles it around plants to keep the deer away-which works sometime...
Book I'm reading has ghetto thieves who are burglars and talking about stealing human hair wigs that are directional hair vs. thrown away hair-reminded me of this thread-sort of.  ;D
Neighbors of mine kept  Hoflingers but would not pasture them away from the house, afraid thieves would come in the night with shears to clip the manes and tails for their long blond hair, valuable stuff that.
These tips, Tom, are right on, helping to jog my memory, I am by no means a plasterer, but treating the substrate to lessen water getting sucked from the mortar is one I'd forgotten. Not one to go for brand name products I've always just used aliun mixed in water to coat thirsty surfaces. However I will forgoe the Portland and in place try locating trass or puzzolan to adjust the lime for these conditions. 
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Nebraska

 

 
Been following  along in this thread, just throwing a picture up.
That pile in the back ground is waste from acetylene production not far from the office. It gets spread on fields for crop production around here...  I've always wanted to build a cabin with a stone foundation. (Just because) Mortar wouldn't be the issue as the lime and sand  is no problem. Stone of quantity and size is the issue and yeah maybe time....

DonW

Remember what Tom always says, "fresh" lime. Which begs the question, what fresh? Freshly burnt, freshly slaked, freshly packaged? I know it doesn't mean fresh from the time you get it in your grubby hands. 
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Tom King

Even the freshly hydrated product still has some unattached Oxygen arms on the loose.  Even the ones that are attached to a Hydrogen atom will readily give it up when a CO2 molecule comes along.  I doubt they dilly-dally in packaging it up.  If it's light, and fluffy, it's good.  It won't stay light, and fluffy long, even inside the plastic bag lining in the bags.

If you're old enough to remember the Apollo Moon Missions, you may remember the Moon dust sticking to everything.  That's because it's a large percentage CaO-Quicklime. Those unattached Oxygen "arms" will bond to Many things.  If we could sift 400 billion metric tons of Moon dust on the upper atmosphere, it would cure climate change by absorbing enough CO2 to lower the temp by a couple of degrees.

Don P

There was a Union Carbide plant near the mine I posted a link to back in the day, calcium carbide + water makes acetylene gas, yet another use of limestone. There is an old dogtrot log cabin in the county that had gaslight back in the day. The carbide generator is still in the back yard, a house sized version of an old miner's lamp.

 When you get hydrated lime that has been sitting around in our climate it is a lumpy mess. The humidity and co2 is working on it and it is trying to become a rock again. In reading, quicklime should be slaked within a week of burning. If it is bagged hydrated lime it is wanting to finish slaking. If you are slaking quicklime, the longer the better. 

More from reading;
QuoteBinders can be broadly classified as non-hydraulic or hydraulic. The hydraulic binders harden through a chemical reaction with water making them impervious to water and therefore able to harden under water. Portland cement, blast-furnance cement (super sulphated), pozzolanas and high- alumina cement belong to the hydraulic binders. High-calcium limes (fat or pure limes) are nonhydraulic since they harden by reaction with the carbon dioxide in the air. If, however lime is produced from limestone containing clay, compounds similar to those in portland cement will be formed, i.e., hydraulic lime.
QuoteNon-hydraulic lime is also produced from limestones with a high content of magnesium carbonate. It is less easily slaked, but some of the magnesium oxide remaining unslaked may carbonate and produce greater strength than high-calcium lime.
Hydraulic lime is produced by mixing and grinding together limestone and clay material, and then burning it in a kiln.
It is stronger but less fat or plastic than non-hydraulic lime. During the burning the calcium oxide from the limestone will react with siliceous matter from the clay forming dicalcium silicate. This compound may react with water forming 'mineral glue'- tricalcium disilicate hydrate. The reaction is slow and may take weeks or months, but after some time a very good strength is achieved.
Which leads to a question. If hydraulic limes set in the presence of water, how is it slaked without it setting up?

Portland cement;
QuoteWhen cement is mixed with water the chemical reactions which are so important for the hardening start. The most important is the forming of tricalcium disilicate hydrate, 'mineral glue', from hydrated calcium oxide and silica.
Pozzolans;
QuoteA pozolana is a siliceous material which, in finely divided form, can react with lime in the presence of moisture at normal temperatures and pressures to form compounds possessing cementious properties. Unfortunately the cementitious properties of pozzolana mixtures are highly variable and unpredictable.
A wide variety of materials, both natural and artificial may be pozzolanic. The silica content constitutes more than half the weight of the pozzolana. Volcanic ash was the first pozzolana used when the Romans made concrete from it for many large and durable buildings. Deposits of volcanic ash are likely to be found wherever there are active or recently active volcanoes. Other natural pozzolana are derived from rock or earth in which the silica constituent contains the mineral opal and from the lateritic soils commonly found in Africa. Artificial pozzolana includes fly ash from the combustion of coal in thermo-electric power plants, bumt clays and shales, blast furnace slag formed in the process of iron manufacture, and rice husk ash and the ash from other agricultural wastes.
The energy requirement for the manufacture of portland cement is very high. By comparison, lime and hydraulic lime can be produced at less than half the energy requirement, and natural pozzolana may be used directly without any processing. Artificial pozzolana requires some heating, but less than half as much as is required for lime production.
Pozzolana and lime can be produced with much less sophisticated technology than portland cement. This means that pozzolana can be produced at relatively low cost and requires much less foreign exchange than cement. However, it takes two to three times the volume of pozzolana required to make a concrete with the same strength as with portland cement and this adds to the cost for transport and handling.
The main use of pozzolanas is for lime-pozzolana mortars, for blended pozzolanic cements and as an admixture in concrete mix. Replacing up to 30% of the portland cement with pozzolana will produce 65 to 95% of the strength of portland cement concrete at 28 days. The strength nominally improves with age since pozzolana reacts more slowly than cement, and at one year about the same strength is obtained.

DonW

I wish I knew more about using hydraulic, very specialized work . It is certainly available to me when I'm in the Netherlands.  I've used trass or puzzolan a few times when I wanted either a shortened hardening timespan or more water resistance or more hardness. Equal parts puzzolan to lime.   In a way it simplifies using lime while not sacrificing a thing since the period the work requires protecting is significantly shortened. When the requirements of a the work demand more water resistance than lime with puzzolan can give then you move the on to hydraulic. I experimented with adding old brick slurry and this had similar effects. It also has a dramatic effect on the color. 
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Don P

I'd offer to have family smuggle it in but their bags are already full of speculaas spice and eatibles  :D

DonW

Hjartum yxa, nothing less than breitbeil/bandhacke combo.

DonW

I hate to say it Tom, but the wasps here make a better plaster than the plasterer, and from local materials.


Hjartum yxa, nothing less than breitbeil/bandhacke combo.

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