Talk:Lime mortar

2 Preservation Briefs
The National Park Service U.S. Department of the Interior, 2 Preservation Briefs, Repointing Mortar Joints in Historic Masonry Buildings,Robert C. Mack, FAIA, and John P. Speweik,is a great guide to help answer questions about Lime Mortar. Topics include....

»Historical Background Identifying the Problem Before Repointing »Finding an Appropriate Mortar Match »Properties of Mortar »Mortar Analysis »Components of Mortar »Mortar Type and Mix »Budgeting and Scheduling »Contractor Selection »Execution of the Work »Visually Examining the Mortar and the Masonry Units »Summary »Conclusion »Selected Reading --HLHiatt (talk) 20:46, 28 September 2010 (UTC)

There is no such thing as a "Pozzolana." It's "Pozzolan." "Pozzolana" is the first known type of a "Pozzolan." Google it. Goffchr 00:15, 2 December 2006 (UTC)Goffchr

Have removed the reference to compressive strength as it is wrong. NHL is classified in stregth bands - NHL 3.5 must be between 3.5 newtons (min) and 10 newtons (max)at 28 days, when mixed according to the test procedures in the standard. —Preceding unsigned comment added by Jmoer (talk • contribs) 12:45, 5 September 2007 (UTC)

Caution should be exercised on historic sites where there is reason to suspect salt contamination. Salts can be introduced to masonry materials due to rising damp (sea salt, soluble ground salts such as nitrates, etc.) and acid rain. Some cleaning techniques can also introduce salt to masonry. Laboratory testing is needed to ascertain salt levels: under 300 ppm is inconsequential; up to 1100 ppm is manageable; and over 1100 ppm is highly problematic when using lime mortars. Salt drawn into fresh mortar will prevent proper setting and result in a material similar to gypsum. Early failures can be expected when lime mortars are used in restoration of salt contaminated bricks. Lime has the potential to perform well in the presence of salt (once it has set up properly) but can not achieve that level of performance when the masonry units have been contaminated with salt. CWNorman@CWN-aia.com —Preceding unsigned comment added by 70.145.63.29 (talk) 17:17, 30 August 2008 (UTC)

Lime with Cement section
Proportions given don't specify materials so they're useless, especially from an encyclopedic POV. Anyone able to clarify? --mikaultalk 01:37, 21 July 2009 (UTC)

Lots of Incorrect Information
First, the history is all wrong. Both in Europe and in North America, lime was not replaced by portland cement in the 19th Century, but by low-fired hydraulic cements produced from argillaceous (high clay) limestones. In Europe, it was called Roman Cement (no connection to the cement produced by the Romans) and in North America it was called Natural Cement. Natural and Roman cements were the dominant hydraulic binders on both continents throughout the 19th Century, with portland cement only achieving market dominance at the turn of the 20th Century.

Next, the inference that portland cements (or natural cements for that matter) are inappropriate for historic restoration is simply false. Tens of thousands of historic buildings (if we select pre-1900 as an arbitrary definition of "historic") were built with these hydraulic cements. Nowhere in the restoration mainstream has there been any credible argument made for restoring natural cement or portland cement buildings with lime. In-kind restoration is generally the agreed-upon default, provided original materials are available, performed well in the first place and are known to work as well in restoration as they did in original construction. (NOTE: An earlier comment on this page correctly references the failure of lime as a restoration material in salt-contaminated masonry. This would be justification for rejecting lime in such applications in favor of an alternative that works better, such as natural cement.)

Finally, references to combinations of lime and cement being unacceptable is highly controversial and not settled technical fact. While the Smeaton project concluded that mixtures of cement and lime lower than 1 part cement to 1 part lime may be prone to early failure, there are thousands of buildings built and/or repointed with ASTM C270 Type O mortar (the proportion specifications of which include 1:2:9 cement-lime-sand as a possible proportion) which have not failed prematurely. The RILEM historic mortars committee, currently developing a new standard, has concluded that portland cement or other hydraulic cements can be added to non-hydraulic limes at levels as low as 10% without negative results. Edisoncoatings (talk) 03:47, 6 October 2009 (UTC)edisoncoatings@msn.com

I would suggest what I found to be an excellent reference, the book by Patrick McAffe "Lime Works" "using lime in traditional & new buildings". "Commissioned by by the Building Limes Forum Ireland". ISBN 978-1-906-429-08-9 — Preceding unsigned comment added by 4.91.103.236 (talk) 00:36, 7 October 2012 (UTC)

Mix section, quicklime not putty
I do not want to edit the article directly since people might reference this to obtain a recipe but the information in the mix section might be misleading as it directly advises that in the 1:3 ratio, lime putty should be used. From what I have been reading (for example in http://www.buildingconservation.com/articles/mythmix/mythmix.htm ) this ratio should be for quicklime and also should be describing the addition of water. The water is added to the quicklime until a paste consistency is achieved, then the 3 parts sand are dumped on top and left for a while before the whole thing is turned and mixed completely.

If we use 1:3 quicklime:sand and added water as my information suggests, the discrepancy between the historical findings and the putty recipe is explained: "analysis of mortar samples from historic buildings typically indicates a higher ratio of around 1 part lime to 2 part aggregate/sand was commonly used". The recipe on a 25kg sac of Holcim NHL5 lime I recently bought in France is as follows: 25kg quicklime powder (about 20 litres from bag measurements), 60 litres of sand, 11 litres of water. This would result in a mix of 20+11 : 60 which is approximately 1:2 which agrees with the historical findings.

Can somebody with actual experience please verify that all this actually makes sense? —Preceding unsigned comment added by Aris637 (talk • contribs) 21:47, 21 July 2010 (UTC)

I make and apply lime plaster as well as consult as a specialist and the question of how much water should be used is often specified by academics. What the academics fail to appreciate is that it is a fruitless ratio. To put it simply you apply water to all mixes until 'fat'. Please don't complicate it with ratios because it will never work due to aggregate particle size and shape as well as the time you take to mix it, weather or not it has been, or will be banked up and how much rain or sun we had on the tested sand the day before. Drop the idea that water can be determined, it will only serve to confuse and mislead.--J.orsi (talk) 15:44, 12 January 2012 (UTC)

I changed the order of the mix components (cement-sand-lime) to cement-lime-sand, to match what I believe is the order in the ratios given. — Preceding unsigned comment added by 152.91.8.11 (talk) 03:19, 9 October 2015 (UTC)

Completing the cycle
It is stated that hydrated lime (Ca(OH)2) eventually turns back to calcium carbonate (CaCO3) by combining with carbon dioxide (CO2) from the air, but this obviously does not add up. The end products of the cycle are calcium carbonate AND water (H2O). This is correctly stated in other sources, but I have not seen any explanation of what happens to the water released. As lime mortar is porous, presumably the water migrates to the surface and evaporates. Or does some of it remain permanently in the mortar, retained by capillary attraction? Can someone who knows the score add something?109.146.48.57 (talk) 18:21, 12 May 2015 (UTC)


 * I'm not sure of the chemistry details in this case, but I suspect the water becomes a hydrate, a dry solid. You may know that copper sulphate is a solid dry blue crystal, but it also contains water, and if you heat it to the point where the 'hidden' water leaves it, it becomes anhydrous, a dry white powder. To be a solid cement seems to imply that water is retained in a dry crystal.31.51.85.128 (talk) 18:51, 12 May 2016 (UTC)


 * Someone tidy-minded can clean this current comment up after it's entertainment value expires. I just wanted to note the occasion, apparently I answered just now, a question that is exactly a year and a half-hour older than my reply! Apparently my TARDIS is on the blink, again...31.51.85.128 (talk) 18:56, 12 May 2016 (UTC)

random other tips
earlier i left a bad comment due only to my not seeing hydrualic/non-hydraulic were in two sections (if they were, perhaps i did see correctly)

according to some, brick layers still use lime (needs citation). perhaps it depends on what brick is being used - meaning perhaps lime is not used with special building bricks that are far tougher - but not all brick would be of that class.

here are some other hydraulic lime tips

Fast Setting Hydraulic lime is fast setting, it can be used on-site just as efficiently as modern cement. Hydraulic It sets by hydrolysis, this means it will also set underwater. Excellent for marine construction or masonry exposed to severe weather conditions. No Shrinkage Shrinkage cracks in mortar and render are virtually eliminated due to its hydraulic setting characteristics. Breathable It is breathable (vapour permeable), absorbing and evaporating moisture from surrounding masonry. This also helps to protect the masonry, there is less risk of salt and frost damage. Flexible It has a low modulus of elasticity. This means it is extremely flexible and allows for movement and thermal expansion. Adaptable Available in NHL 2, NHL 3.5 and NHL 5 grades. This allows design of mortars suitable for masonry of varied density and degrees of weather exposure. Workable It is supplied in powdered form, it is pretty much the same as mixing and working with a modern cement. Mixed to the right consistency, hydraulic lime mortar, render or plaster are beautiful materials to work with. Sympathetic It is softer than modern cement, a softer mortar will not wear away the surrounding masonry over time. Bricks and stones are also reclaimed more easily if dismantled. Aesthetic Hydraulic lime mortars are indistinguishable from non-hydraulic limes. They carry the same chamring, traditional appeareance.

finally: lime doesn't support mold, which is why it is used as a wall plaster and (was a) substitute/ingredient in place of gypsum

is it as high volume and strong as portland cement? no. however bricks on very tall building aren't structural and is loath to be put too many floors high (ie, on a high-rise, hanging glass on the iron frame is preffered). what that says is: sure mortar with no lime might be stronger with special bricks but you are only going so many floors high with that - so it's a matter of the number of floors "exactly allowed by code".

it lime useful? yes. do manufacturers use it in products that are in hardware stores (mortar, stucco, plaster, drywall compound)? variably, yes. should the article say lime, a bulk stone found mined in large quantity is a thing of the past and no longer as useful? no. thank you i'll be asking for that bag of type-S lime.

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