Is Hydraulic Mortar All It Claims To Be ? - Masonry - Contractor Talk

Is Hydraulic Mortar All It Claims To Be ?

 
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Old 06-19-2016, 11:50 AM   #1
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Is Hydraulic Mortar All It Claims To Be ?


Several weeks ago,I needed to do some spot pointing on a 1870,s brick home. The brick and most joints were in very good condition. The building was of the Italianate style with exceedingly wide eave overhangs. Perhaps,the wide overhangs were a contributing factor for the good shape the masonry was in,offering a certain "umbrella" affect.


Anyway,matching the existing mortar was a key element for the scope of the job. With my profound dislike of mortar dye "guessing" I opted to take the easy way out. I pulled out my color chips from the well known French import dealer and ordered away.


The color match was as close to spot on as one could hope for. Having used their product before,I was well aware of the reduced work ability of their hydraulic mortar ( NHL 3.5).


This job prompted me do do a bit more reading regarding hydraulic mortars and the usage of pozzolans with lime mortars. This is some of the information I ran across. Several papers discounted the need for using a hydraulic mortar. Some reasons given,hydraulic mortar reduces the permeability of lime mortar. NHL 5 having close to the same drawbacks as a OPC mortar. NHL 3.5 not far behind. The usage of pozzolans were said to have similar characteristics of hydraulic mortars,depending on the type. Brick dust having the least comparable aspects to hydraulic mortar.


With all this said,if it was not for the need to match the existing color,I could have accomplished the same results with a 1:2: 7.5--9 mix.Not to mention the $160.00 for 114 lbs.of mortar.


Somehow,this experience felt like an exercise in futility at best and smoke and mirrors at the worst.
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Old 06-19-2016, 12:44 PM   #2
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Re: Is Hydraulic Mortar All It Claims To Be ?


Hydraulic lime has been popular in my area for about 20 years now, especially for exterior work. It is quite reliable and does seem to improve many of the damp problems caused by the use of OPC in older buildings.
It does need mixing up for about 20 minutes and then left for 20 before using though.

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Old 06-19-2016, 05:54 PM   #3
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Re: Is Hydraulic Mortar All It Claims To Be ?


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Originally Posted by stuart45 View Post
Hydraulic lime has been popular in my area for about 20 years now, especially for exterior work. It is quite reliable and does seem to improve many of the damp problems caused by the use of OPC in older buildings.
It does need mixing up for about 20 minutes and then left for 20 before using though.



Several of the papers I recently read that spoke out against the usage of hydraulic lime originated in the U.K..Their primary reason to not recommend there usage was the fact that they reduce the permeability of the mortar. Also, a NHL 5 has characteristics not dissimilar to a OPC mortar.

Having just recently worked with a NHL 3.5 AND noticing the reduced work ability in comparison to a 1:2 : 8--9 mix ;if they both characteristically reduce permeability,why bother ? Especially when one factors in the close to exorbitant price of the NHL,what is the advantage / justification for its usage?
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Old 06-19-2016, 06:08 PM   #4
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Re: Is Hydraulic Mortar All It Claims To Be ?


This paper claims a hydraulic mortar is unnecessary. However,section 10.1 also claims a pozzolan additive does not reduce permeability.That premise is refuted in numerous other papers I recently read on the subject.


I find this rather interesting that the gurus cannot seem to get on the same page.


file:///C:/Users/Fred/Downloads/Pointing-with-Lime-Mortars-ENG_439kb%20(2).pdf
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Old 06-19-2016, 08:26 PM   #5
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Re: Is Hydraulic Mortar All It Claims To Be ?


I have never played with hydraulic mortars, so I am out on that aspect of the question. I do think that small amounts of either pozzolons or OP, in the range of less than 2% (by volume of cementious materials) can not affect the permeability of the mortar to a great extent but do allow for an initial set, if not better workability.
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Old 06-20-2016, 04:10 AM   #6
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Re: Is Hydraulic Mortar All It Claims To Be ?


It is a good question Fred as to why use NHL. The problem that we have as construction tradesmen compared to mechanical engineering tradesmen etc, is that it can take 20 or 30 years to see the results of the wrong mortar mix, whereas putting the results of putting wrong oil in an engine etc, can be seen in a much shorter timescale.
To some extent we have to rely people in the labs, or what we learn from other tradesmen.
However I know of homeowners who have said that replacing a concrete floor with a limecrete NHL 5 floor has cured their damp problems, as with pointing with NHL 3.5.
Hydraulic lime is much cheaper here, and if it cost as much as you were paying I think it's use would be less common.
The 1/2/9/ OPC/lime/sand was used on older properties up to about 20 years ago, but nowadays it's not recommended.
The use of Hydraulic lime is generally not allowed in properties owned by the National Trust, English Heritage or Listed buildings, as an Air lime with a pozzolan is prefered.
There was a rumour that the French were adding small amounts of OPC to their NHL to aid setting.
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Old 06-20-2016, 07:57 PM   #7
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Re: Is Hydraulic Mortar All It Claims To Be ?


I will say this,I respect the input from the Ct members,while there may not be a bunch of letters following their names,there is a very considerable amount of common sense and many years of hands on experience held collectively in the group. The list of discrepancies I read the last two weeks or so regarding NHL,and pozzolans would be enough to fill a book. All this disagreement was voiced by the so called guru /experts in this field.


There are two topics I will elaborate on regarding the experts opinions. First,many, many experts insist that gauging a fat lime mortar with anything less than 50 % OPC is the kiss of death for the mortar and it is destined to fail. Tscar has mentioned several times of the good success of gauging with around 10 % OPC. I trust his experience and I have other reason to believe it is not detrimental. Close to 30 yrs.ago,(long before I read all this mortar stuff) I cut and pointed a 1870,s building in the adjacent town. Not knowing any better,I gauged the mud with a "dash" of OPC,about 5 %. The building has a gable roof pitching N.-S ,shallow overhangs,no gutters,brick foundation,no basement. After 30 yrs.very little mortar wear,only place noticeable,the bottom 16". Mind you,no spalled bricks and the base of the wall has constant rain splash coupled up with rising damp. IMHO,this mortar is doing what it is supposed to do, deteriorate,obviously it is the sacrificial element in the wall.



Secondly I love the quote of Mike Edison of Edison coatings,he says "hydraulic mortar is very historical........except it is not part of our history,limestone yielding such is not indigenous to the U.S. and consequentially,is not part of our building history".

To use it here is probably not a horrible thing.......it is just introducing a foreign ingredient into our building fabric.


BTW Stuart,yes the cost of three 38 lb.bags of ready to go (pre sanded) NHL 3.5 was $ 160.00 Yankee greenbacks ! As one can readily see,to build new construction other than a dog house with such mud is cost prohibitive, unless one has the resources of Bill Gates.,
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Old 06-27-2016, 08:53 PM   #8
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Re: Is Hydraulic Mortar All It Claims To Be ?


Quote:
Originally Posted by fjn View Post
The list of discrepancies I read the last two weeks or so regarding NHL,and pozzolans would be enough to fill a book. All this disagreement was voiced by the so called guru /experts in this field.


There are two topics I will elaborate on regarding the experts opinions. First,many, many experts insist that gauging a fat lime mortar with anything less than 50 % OPC is the kiss of death for the mortar and it is destined to fail. Tscar has mentioned several times of the good success of gauging with around 10 % OPC. I trust his experience and I have other reason to believe it is not detrimental. Close to 30 yrs.ago,(long before I read all this mortar stuff) I cut and pointed a 1870,s building in the adjacent town. Not knowing any better,I gauged the mud with a "dash" of OPC,about 5 %. The building has a gable roof pitching N.-S ,shallow overhangs,no gutters,brick foundation,no basement. After 30 yrs.very little mortar wear,only place noticeable,the bottom 16". Mind you,no spalled bricks and the base of the wall has constant rain splash coupled up with rising damp. IMHO,this mortar is doing what it is supposed to do, deteriorate,obviously it is the sacrificial element in the wall.



Secondly I love the quote of Mike Edison of Edison coatings,he says "hydraulic mortar is very historical........except it is not part of our history,limestone yielding such is not indigenous to the U.S. and consequentially,is not part of our building history".

To use it here is probably not a horrible thing.......it is just introducing a foreign ingredient into our building fabric.

I read this and that about lime off and on fairly often. Type S lime, Type SA, High calcium lime, hot lime, hydraulic limes, pozzolans, brick dust OPC etc etc etc. Best thing is a high calcium lime putty derived from hot lime with no or very few additives, but it requires babysitting which is time consuming/expensive. Good for publicly funded projects and vanity projects but lets face it there's a reason everyone jumped ship in the '40's.

So if you want something that is softish, permeable, easily acquired, and reasonably priced you need to mix your own with either a site mixed NHL or bagged hydrated Type S or SA lime gauged with some sort of a pozzolan. All the studies I have read have basically said that NHL 2 won;t be problematic in any way to the material but it needs at least a week if not more of tending. As you go up the scale in terms of hardness you also loose permeability and the BIG problem is that the NHLs are measure at the infamous 28 day point...but they can and usually do continue to climb in strength....and loose permeability....for quite a while longer. So what starts at a 3.5 may end up as a 3.8 or 4.3 or?? and if course the permeability is going down the whole time

A 1;2:8 Type O mortar has actually had very good results in about all the studies I've read except for those done by the NHL manufacturers. Most are from N American govt institutions as well as from sources like Graymont who produces both hydrated lime AND Porty...so that view is likely as skewed as those from the NHL producers. But a (British living in Canada for the last 30 years) fellow I talked to who is a real muckity muck in the mortar world (conservator, consultant at parliament and dozens of heritage projects yearly as well as a travelling mortar lecturer) basically called NHL snake oil, or at least at it's mention said meh...not that it was bad but that it wasn't worth the cost ( a bag of NHL 3.5 costs $38 retail before discount if you're buying less than a palle, a bag of type N costs $9.50, a bag of porty or lime $12). When I asked him about pozzolans like kaolins he said that the results he has seen were about the same as portland, sometimes better sometimes worse but always close.

Except brick dust. But where do you buy brick dust? and who wants red brick dust turning your mud pink? You need to gauge it at the same ratio as the lime to get a good result and that is a ton of brick dust...We didn;t have time to get into type K which is a shame

My own personal totally non scientific experience has been that if you mix OPC and hydrated lime to make a Type O or Type K the portland separates out after time and comes to the front of the joint where it creates areas of low permeability...and it's ugly because you have gray blotchy areas. But I have at times mixed Type N masonry cement which around here has NO lime in it, only Porty and plasticizers and anywhere from 1/4 part lime to 2 parts lime (bagged hydrated type S lime) and I havent seen the same results. I find it interesting, but the oldest sample I've seen was only 10 years old so I don't know.

Basically just do anything cause in 10 years SOME ONE will tell you you did the wort thing you could ever do...
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Old 06-27-2016, 08:57 PM   #9
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Re: Is Hydraulic Mortar All It Claims To Be ?


Oh...not sure if the comment about NHL not having any history in N America is quite true. Many small scale lime kilns would have been producing a feebly hydraulic lime unless they were burning seashells or bones exclusively. Most limestones have a measure of clay in them and would produce a hydraulic lime to some degree. I suppose chalk or marble not so much
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Old 06-27-2016, 09:53 PM   #10
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Re: Is Hydraulic Mortar All It Claims To Be ?


Lots of shells were used to make lime up here back when. Small operations.
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Old 06-28-2016, 11:59 AM   #11
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Re: Is Hydraulic Mortar All It Claims To Be ?


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Except brick dust. But where do you buy brick dust?

.
http://cornishlime.co.uk/brick-dust-pozzolan-20kg
P+P might cost you though.
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Old 06-28-2016, 06:45 PM   #12
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Re: Is Hydraulic Mortar All It Claims To Be ?


I used to recommend up to 10% gauging materials, but I am down to around 2%, be it Portland, brick dust, or pozzolans. The best source of brick dust is your own saws, you are making it every day, harvest it. I am not even a contractor and have 2 five gallon buckets of it, one red, one grayish. That will do a lot of tuckpointing mortar, and at 2% it doesn't change the color any more than our (red) sand does.
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Old 06-28-2016, 06:50 PM   #13
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Re: Is Hydraulic Mortar All It Claims To Be ?


Dom; regarding the brick dust,depending on who you read,it goes from not diminishing permeability,to like all the rest to we do not know yet.


My 20 + years "study" I posted with a dash ( 5 % opc) goes against all I read. Yet I have had good results and several times Tscar mentioned positive results with that approach also.

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