Bagged Premixed Lime Mortar For Tuckpointing

 
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Old 10-16-2012, 08:33 PM   #141
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Re: Bagged Premixed Lime Mortar For Tuckpointing


NO. Type O is the exact opposite of what you posted. 1:2:9 being portland:lime:sand

type M is 3:1:12
Type S is 2:1:9
type n is 1:1:6
Type o is 1:2:9
Type k is 1:3:12

And no type M S N are NOT good for most situations. they are no good for any area that has a softer mortar used deeper in the wall or for any material that softer or less permeable than the mortar. MANY limestones and sandstones would deteriorate quickly with a type S mix, even a type N. I've seen old brick that broke up in less than a decade after being pointed with a type n

Except for the OP I don't think anyone is talking about premix mortars.
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Old 10-16-2012, 10:56 PM   #142
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Re: Bagged Premixed Lime Mortar For Tuckpointing


I actually meant what you said...the wording may need tinkering. I actually stated that the Type O mortar is 1:2:9 with the Portland being 50% of the Lime (1 Portland: 2 part Lime)...so I don't see what the error is in that part.

As far as the part about Type M, S, N, O being safe I meant that it is safe from the rule that the Portland must not be less than 50% of the Lime to not be considered as weakened mortar compared to pure hydrated Lime mortar...as a reply to this:

Quote:
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
But, I've changed the wording there because my wording implies safe in all mortar usage situations...not what I meant!

Last edited by timp; 10-16-2012 at 11:17 PM.
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Old 10-16-2012, 11:53 PM   #143
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Pure lime mortar, old style lime, not hydraulic, not double hydrated, has survived for hundreds of years in Northern climates in exterior applications with minimal erosion. Best practices is open to debate on the subject of restoration mortar, and I am not convinced one way or the other. Physically or structurally, I do not see much difference between a hydraulic lime or a hydraulic Portland cement, nor do I have confidence in the specifications prepared for most restoration work by architects and engineers that do not have the skill set to evaluate either.
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Old 10-17-2012, 12:42 AM   #144
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Re: Bagged Premixed Lime Mortar For Tuckpointing


I've recently been reading a book about the history of cement and concrete called "Lea's Chemistry of Cement" by Peter Hewlett amongst other things. It's interesting to see that things are not always black and white...lot's of grey areas to think about.

For example, the people have analyzed samples from the kilns of "inventor" of Portland cement Joseph Aspdin and came to the conclusion that although he owned the name and patent for Portland cement...he had actually created a type of prototype of cement that is not what we now consider Portland. He created a calcined calcium-clay cement similar to hydraulic lime... without the thermal breakdown and blending of silicates and calcium into dicalcium-silicates and later tricalcium-silicates that comes from the extreme 2500 F degree cooking. And, going back farther in time they have discovered hydraulic lime cements in structures that had contents (tricalcium silicates) which approached modern Portland cement.

In other words... get a more powerful oven if you want the calcium (lime) and silicates (clays) to chemically mix into the really strong stuff.

Also, I've watched videos of French origin of a guy advertising and explaining his companies hydraulic limes for sale to the US and explaining that no hydraulic limes are actually 100% hydraulic limes but contain fillers such as limestone dust and non-hydraulic lime.

Also, there is the issue of where the source of the naturally hydraulic lime is from and that each deposit location of natural hydraulic lime contains widely varying contents and ratios of Calciums, magnesiums, clays and the like.

The difference between Portland cement and hydraulic limes appears to come down to such things as percent clay content and how high of a kiln temperature it's all heated. Hydraulic lime comes from heating calcium carbonates with clays to just before incipient fusion (beginning to melt and fuse). Portland production cranks the heat up all the way past fusion when those silicates are really melting and combining with calciums.

The more you know the better off you can be in the long run. I do know that since I've been mixing my own mortars I've been very excited by how smooth and plastic I've gotten my mortars by tweaking a bit more lime and a little less sand to get that perfect trowelling creamy peanut butter texture which actually becomes fun to apply because it's not dripping and falling all over the place.

It's also interesting to realize that from a chemist's point of view that hydraulic lime and Portland cements are just forms of "calcerous" cements...meaning lime containing.

I haven't used Natural Hydraulic Lime yet. That's next on my list. My experience with hydrated lime powder so far is that in a 1:1:6 ratio with Portland and tweaked a bit with a little less sand spreads like peanut butter and I like it. Hydrated lime and sand by itself does spread like a dream (especially when you let the lime putty sit) but I'm very suspect of it's strength and it does remind me of weak indoor plaster as it dries slowly to that chalky consistency.

I want to try another hydrated lime plus calcined metakaolin mortar experiment, but the problem is that the proportions and contents are important and my source of china clay is unmarked bags that no one seems to know exactly the contents and strength or whether it's calcined. This means that I can't really rely on what I'm mixing... which makes it just an experiment. The Metastar metakaolin is only distributed through a salesman's appointment. I haven't called yet but I fear it may be only for large shipments intended for concrete ReadyMix industry. I wish you could just buy it at the local Home Depot when you need it.

Caution:
When you start playing with lime powders more often you need to get those chemical proof gloves, tighter fitting goggles, and maybe a dust mask... and carefully slice open the bags and measure/ pour slowly to avoid dust poofs. It pays to shop for the tightest fitting glasses to keep your eyes clean in the long run. I'm using a Stanley RST 61035 right now which is reasonably priced and fits close.

This guy seems to REALLY be into lime mortar restorations:
http://speweikpreservation.com/about/

Last edited by timp; 10-17-2012 at 01:31 AM.
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Old 10-17-2012, 08:44 AM   #145
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Re: Bagged Premixed Lime Mortar For Tuckpointing


I'll have to look up the smeaton project again because I thought their claim was that Portland at less than 50% of the cementitious materials displaced the lime and created permeability problems.

You're dead on in thinking that NHL's and Portland are very similar.

Another way of looking at it is

Pure lime= calcium carbonate (Pure limestone or marble)burned at temps around 800* (I remember the #'s but I can't remember if it's Celsius or Fahrenheit but I believe it's Celsius) Of course it's later slaked

NHL's= at least 66% calcium carbonate and clay at most 33%. OR a limestone that has been formed with up to 33% magnesia, alumina and silicates and burned at 800* The more CaCO3 the less hydraulic the lime

Portland= Calcium carbonate at 60-65% and clay at 35-40% OR a limestone containg the same 35-40% alumina, magnesia and silicates burned at 1200* or more

And yes the original Portland cement was made by burning a Limestone that had a high level of impurities, so it was basically the most hydraulic of the NHL's

I like to think of all of this in relation to baking. You can make pancakes from scratch, you can make them where you add bisquick, eggs and milk, or you can make them by just adding water to a mystery powder. You can also flip the proportion of eggs/milk mixture to flour and come up with crepes, or you can take the mystery powder and add more water and get something that is very similar to crepes etc... And you can look in 10000 recipe books for all these recipes and come up with slightly different proportions for each recipe you find. To say that ONE recipe makes pancakes and is the only correct one is nuts. You can also come up with a million arguments as to why any one recipe is heathier/tastier/better. The same goes for mortar. There is no ONE correct proportion or mix. each circumstance requires it's own mix. As you said, lots of grey areas.

And I do agree with Tsacarborough that a 1:3 lime sand mix has worked for centuries and should still work, however... it needs to stay hydrated for a week or more to set properly If it's chalky and is falling out after it's installed my guess is that it was allowed to dry out and didn't have time to cure.
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Old 10-17-2012, 09:30 AM   #146
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Dom

Great analogy with the pancakes. Mystery powders are always suspect too! I will say that I can guess why people ran to Portland from limes is that pure limes are way too slow to set, require that longer wetting period and are so burning of eyes and skin. As people return to limes they will have to return to confronting these problems...but... with possibly more creative solutions obtained with advanced knowledge.

I can't emphasize enough...shop for the best fitting goggles, and don't feel silly having people who are mixing wear respirators during the dusty phases. Also, I've upgraded to coated gloves for lime projects. Save your eyes, hand skin and lungs for the future.
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Old 10-17-2012, 09:54 AM   #147
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Re: Bagged Premixed Lime Mortar For Tuckpointing


The reason Portland displaced lime in mortar has to do with preparation of the mortar (slaking the lime) and to a lesser extent the curing requirements.
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Old 10-17-2012, 04:04 PM   #148
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Re: Bagged Premixed Lime Mortar For Tuckpointing


But as I understand the primary benefits (aside from workability concerns or the issues of longer set times) of lime:sand mortar over OPC:Lime:sand or Masonry cement based mortars is a) lower compressive strength (i.e., less than the masonry unit) b) autogeneous healing capacity and c) vapor permeability.

The vapor permeability point is interesting to me - I've read that concrete (OPC+Sand+gravel) acts as vapor retarder if more than 1.5'' and a vapor barrier if more than 5'' thick.

If we have a 1/2'' or less mortar joint, or a 1/2'' parge coat, do we know for sure that even a type M mortar would in so many words "trap water" in the wall?
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Old 10-17-2012, 08:19 PM   #149
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Quote:
Originally Posted by Tscarborough View Post
The reason Portland displaced lime in mortar has to do with preparation of the mortar (slaking the lime) and to a lesser extent the curing requirements.


The curing requirement is an interesting topic in and of itself. Less than a year ago an article was written for Masonry Edge magazine by a engineer & restoration mason about historic mortar/pointing. I contacted the author with some questions. He had a take on the situation that was plausible. His position was that building a mass wall with lime mortar is a different animal from pointing one with such. I tend to agree,in new work the wall is saturated through and through with moisture. In pointing even spraying the wall in a robust fashion is but a feeble attempt to introduce the volume of water present in new work. The most dilligent effort to keep the wall moist falls short of the goal. His take,the mortar just does not have the moisture needed for a complete cure.


Old masons/authors knew the merits of pre wetting the brick prior to laying. In today's age in new work very few take the time to test brick to determine the need for pre wetting. If the need is acknowledged,the wetting is usually superficial (spray with hose) Old masonry books and an old B.I.A. tech note spoke of the procedure. They stated,the brick must be totally saturated yet surface dry.Often a cut away picture dipicted that view of saturated bricks/surface dry. If memory serves,any brick with an I.R.A. 30 grams or more need to be wetted in that fashion. To accomplish total saturation brick need lots and lots of water. The only way to test to see if they are truly saturated is to put one in a bucket of water,if it bubbles,it is not saturated yet.

Bottom line,lack of moisture in pointing with lime is a major concern.
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Old 10-17-2012, 08:38 PM   #150
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Whenever I build with old brick I keep a couple 5 gallon buckets of water with 4 or 5 bricks in it. They can be in there for a minute or longer and when I take them out, they're surface dry in a matter of seconds. If i were to try and use the bricks without wetting they'd suck all the water out of the mortar before I had time to finish laying it. After MAYBE 20 bricks the pail has lost 1/2 it's water, the bricks feel like they're twice as heavy as well. I onc tried to lay some bricks without soaking after it had rained all night, didn't really work. I could lay them but by the time I went to joint them the mortar was junk, had to relay a couple hrs worth of brick
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Old 10-17-2012, 09:15 PM   #151
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Quote:
Originally Posted by mapple View Post
But as I understand the primary benefits (aside from workability concerns or the issues of longer set times) of lime:sand mortar over OPC:Lime:sand or Masonry cement based mortars is a) lower compressive strength (i.e., less than the masonry unit) b) autogeneous healing capacity and c) vapor permeability.

The vapor permeability point is interesting to me - I've read that concrete (OPC+Sand+gravel) acts as vapor retarder if more than 1.5'' and a vapor barrier if more than 5'' thick.

If we have a 1/2'' or less mortar joint, or a 1/2'' parge coat, do we know for sure that even a type M mortar would in so many words "trap water" in the wall?
You might be interestd in this "Comparative Laboratory Evaluation of Conservation Mortars"

http://www.limes.us/pdf/APTI-ComparativeLabEval.pdf

There is a section concerning water vapor transmission rates of mortars as tested using ASTM E96 methods. In short the movement of water through mortar samples immersed in a water dish were measured in grams per meter squared per hour. So, a higher number is better.

The results obtained showed:

1.18 for white Portland,
1.76 for grey Portland,
1.76 for Type N (Portland-Lime),
2.4 for Type O (using high Dolomite lime),
3.4 for Type O (high calcium lime used),
3.51 for high Dolomitic Lime.
4.15 for Natural Hydraulic Lime 3.5,
4.94 for High Calcium Lime (regular lime)

Type M mortar would have the least lime content of the accepted Portland-Lime mortars and likely be similar to plain Portland mortar. Type N mortar in this study came out the same as regular Portland mortar. The binder to sand ratio was 1:2+quarter for the mortars.

The compressive strengths were determined in MPa (Newton/ Meter^2) as follows for 6 month cured samples:

1.76 for high calcium (regular) lime
3.67 for high dolomite (regular) lime
4.15 for Natural Hydraulic Lime 3.5 (appr 600psi)
8.26 for Type O (made with high calcium lime)(1,200psi)
9.89 for Type O (made with high Dolomite lime)
16.34 for Type N (with high Dolomite lime) (2,400psi)
Above 25 (beyond testing limits) for white and grey Portland

Since NHL 3.5 is sold as a medium strength hydraulic lime I'd think that the 3 to 5 range would be a nice compressive strength for an old soft stone building.

This paper has references to other studies of course if you like reading.

Last edited by timp; 10-17-2012 at 09:40 PM.
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Old 10-17-2012, 09:34 PM   #152
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Re: Bagged Premixed Lime Mortar For Tuckpointing


All of the old masonry text books I have read explain how to make sure the brick have the proper moisture content, and it is not by soaking but by wetting the piles (cubes? we don't need no sticking cubes, we unload and stack them all by hand) on the jobsite and they give fairly complete instructions on how to do so. It is rare that modern masons wet the brick prior to use, but here in Texas it is done, especially with the handmade Mexican adobes that are so common.

Saturated, surface dry is the technical term for what is desired for certain conditions and brick, but not for normal modern vitrified face brick.

Water vapor is not the same as liquid water, and with airspace construction as opposed to mass masonry, the behavior of the water in the wall is different.
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Old 10-19-2012, 01:08 AM   #153
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Quote:
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Water vapor is not the same as liquid water, ...
I just checked an Atkinson Noland test of Water Transport Charactersitics of Masonry restoration Mortars and it seems that the ASTM E96 test they used places a square of sample mortar at the top of a cup above the water and sealed so that only vapor can pass. This seems like a better description of a vapor test.

This study tested Water Vapor Transmission, Permeability, and Permeance of the mortar samples. Portland-Lime mortars of Type O and Type K were tested along with brick, St Astiers HHL Lime (three types), lime putty, hydrated type S lime and stone. The mortar samples were fabricated cubes and joints.


http://ncptt.nps.gov/wp-content/uploads/2004-26.pdf

Compressive strengths were also tested here:

hydrated type S -- 115psi at 180 days
HHL Lime 3.5 -- 280psi at 180 days cure
Type O (1:2:9) mortar -- 810psi at 56 days
Type K (1:3:12) mortar -- 475psi at 56 days

I don't know why the other test seemed to suggest the mortar sat in the water. I'll have to re-read that one. This test complied with ASTM E96 also and clearly showed that mortar squares fitted and sealed with caulk in a space at the top of a square container above (and not in contact with) the water. So, water had to evaporate out through the mortar samples tested.

This paper explains that E96 distinguishes between WVT (water vapor transmission), Permeance, and Permeability. WVT is the amount of water in Grams that evaporates through a given surface area over time in hours expressed as g/h*m^2 grams per hour-meter squared. So. a higher number is more permeable.

Permeance is that WVT multiplied by the difference in vapor pressure between the inside and outside of that test container.

Permeablitiy is the Permeance multiplied by the thickness of the sample.

If you have a scientific mind then I'm sure you're all reading this and nodding/ smiling at the obviousness of all this information :- D

WVT selected sample scores:

brick sample -- 3.5
Hydraulic Lime (medium) -- 5.1
Portland-Lime Type O mortar -- 5.4
Portland-Lime Type K mortar -- 5.2
hydrated lime mortar type S -- 7.4

All above expressed in grams per meter hour squared of evaporated water through the sample. So, higher is more vapor permeable.

This test seems to make a Portland-Lime mortar of Types O and K seem fine. But, remember that premixed bags of Types N (for example) do not even have to contain any hydrated lime. They often use ground limestone instead. I don't know if that's as good as hydrated lime. But, I've never seen a premix of Types O or Type K mortars anyway.

The Permeance numbers in the papers should address Tscarborough's concerns because that takes into account the differences in vapor pressures inside and outside the walls. You'd have to have a really sound mind to be able to put those numbers into real world value. Yet... it gives those who are searching for answers a clue.

Wow. That's a lot to think about

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Old 10-19-2012, 12:53 PM   #154
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Re: Bagged Premixed Lime Mortar For Tuckpointing


[QUOTE=Tscarborough;1606097] It is rare that modern masons wet the brick prior to use, but here in Texas it is done, especially with the handmade Mexican adobes that are so common.


I could not agree more with this statement,that was exactly the reason i mentioned that brick is not often wetted on today's jobsites. The lack of wetting does not negate the need to do so if it is warranted. The B.IA. states that brick with an I.R.A. between 15-20 grams offer optimum tensile bond strength. If the I.R.A. exceeds 30 grams wetting is needed. The spec.sheets from the brick maker will present the I.R.A. of each of their brick. A simple test can be conducted in the field,it is as follows. Draw a circle around a 25 cent piece with wax candle,place 20 drops of water from eye dropper in circle,if water is absorbed in one minute or less brick need pre wetting.
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Old 10-19-2012, 04:09 PM   #155
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Great info. I agree - I have never seen pre-mix type O or K. I have found true OPC:Lime type N though. I find it a bit surprising the extra lime in the type K shows a marginal decrease in WVT.

I wonder how type N or S would have fared.

It seems that everyone now accepts that using a modern OPC based to repoint soft brick or stone will lead to damage of the substrate - how much and how fast damage dependent on weather exposure, freeze-thaw cycles, etc.

I wonder how much of the potential for damage is caused by the reduced WVT of the mortar vs reduced absortion rate of the mortar - and most of all, if there is no freeze-thaw action, whether any damage would result at all (removing variables you can't control such as poor workmanship, inaccurate mixing, etc)?
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Old 10-19-2012, 05:21 PM   #156
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Quote:
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most of all, if there is no freeze-thaw action, whether any damage would result at all (removing variables you can't control such as poor workmanship, inaccurate mixing, etc)?
I think this is the most important thing. If you lived in a hot arid area, you could use almost anything as a mortar. Fundi who is a member here is in Tanzania and uses a clay mortar. it wouldn't last a week hr but works well in his area. Adobe is common in southern areas, it too is clay based. Freeze thaw is masonry's worst enemy and in areas that it doesn't occur I'm fairly certain that mortar choice is limited to desired strengths only, tensile and compressive because mortar durability is almost limitless.

Anyone in southern climates is more than welcome to disagree with m because i have no experience with hot arid climates
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Old 10-19-2012, 06:13 PM   #157
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Re: Bagged Premixed Lime Mortar For Tuckpointing


No, you are on point. Here the weakest mortar is always the best mortar, but in extreme freeze thaw and seismic zones that is not always true.
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Old 10-19-2012, 07:22 PM   #158
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Re: Bagged Premixed Lime Mortar For Tuckpointing


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And no type M S N are NOT good for most situations. they are no good for any area that has a softer mortar used deeper in the wall or for any material that softer or less permeable than the mortar. MANY limestones and sandstones would deteriorate quickly with a type S mix, even a type N. I've seen old brick that broke up in less than a decade after being pointed with a type n

Except for the OP I don't think anyone is talking about premix mortars.
I quite agree with Dom on this. Certainly for modern brick and block, Type N or what ever is available commercially will likely suffice. I made a comment on the other thread regarding Type S and N in which I stated that Type N is a great catch all. There are several exceptions to this and old soft brick would be one of the exceptions.
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Old 10-28-2012, 08:02 PM   #159
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Re: Bagged Premixed Lime Mortar For Tuckpointing


Just going to throw this out there.

This past week I did a repoint of a foundation on a building I did some brick repair on earlier in the spring/summer. Some of the brick I repaired sat on top of the foundation i repointed and I had to cut away some of the 4 month old mortar to blend things in. I had used a 4 lime 1 portland 12 or so sand.

when I cut into it, it felt great. It was dense but soft enough to put the chisel in with minimum effort. In fact it felt exactly like the sound lime mortar that I was cutting back too and leaving in the foundation. It felt homogenous and didn`t have any separation that I could see or feel. i remember when I put it in that it was very hot out and I had to saturate the area many times that day with a sprayer. That area doesn`t get any direct sun however. It was also one of the first days of the drought and we didn`t get any rain for 2 months or so. After the morning of the 2nd day I didn`t hydrate the joints again,

Now i know that these joints were only several months old and haven't even been through a real freeze thaw cycle (we have had a few nights of below freezing in the last couple months but not many) but they fly against what all the reading that was just presented tells us. I'm not disputing the smeaton project or any of the other work that people have referenced but for me it was proof enough that Portland used in very small amounts isn't that bad

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