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Why lime mortar is not in commerical use instead of cement?

runitsharma

Lime mortar was used to make forts and castles in past, but now cement has taken over.

Lime mortar has better properties than cement, it's durability is way more than cement. Forts which are standing from centuries are proof of it.

So why it is not used instead of cement in almost every building, house, or any other establishment?

 
Apr 13, 21 11:52 am
Wood Guy

Lime mortar is still in use, mainly for historical restoration work. Portland cement based mortar is more durable. Lime mortar is softer, which is good in some ways but it wears away over time, especially with acid rain. 

Apr 13, 21 12:14 pm  · 
2  · 
rcz1001

True but you can merely repoint the bricks without damaging the soft bricks but with newer masonry units being inherently harder than some of the older masonry units, you can probably get by with some masonry unit consisting of portland cement.

Apr 14, 21 12:11 am  · 
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rcz1001

Cement and lime mortar has differing properties of strength, flexibility/ductility, etc. It depends on what properties you are looking for in the mortar. I agree with you about the acid rain but not just acid rain.

Apr 14, 21 12:24 am  · 
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thatsthat

Most masons barely know how to mix water with the pre-mixed bagged mortar, let alone slake lime, and consistently prepare the proper lime, sand, and aggregate mix using specified proportions.  In the US we largely switched to portland cement mortars in the mid- to late-1800s after the technology was brought to the US from England. Even portland cement has gotten progressively harder over the last century due to the ways in which it is fired in the kiln, the kilns themselves, firing temperature, etc.

Apr 13, 21 2:23 pm  · 
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rcz1001

Actually, the switchover depends on where you are and the masonry units you are using. In a lot of homes, the more portland cement based mortars weren't used until the 1910s to 1930s or so homes in the Victorian age used lime mortar for chimneys and brick foundations. Some did use cement-based mortar with harder masonry units like granite, basalt, etc. 

It varies from place to place and many homes and buildings did have some repointing or tuckpointing at some point in time over its history.

Apr 14, 21 12:15 am  · 
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There is literally a wikipedia page that answers this question: https://en.wikipedia.org/wiki/Mortar_(masonry) 

Note that lime is still used in portland cement based mortars.

Apr 13, 21 2:58 pm  · 
1  · 
rcz1001

First off, the choice or mortar depends on the masonry you use. Since most of today's construction is made of some combination of the three basic structural materials: wood, concrete, and metal (steel or aluminum). Most of the bricks today are harder bricks which may make it safer to use hydrated lime/cement mortar mixes today but older bricks found in historic buildings were often poorly kilned in the first place and barely have glazing at all and so soft that its almost like slightly glazed sandstone. 

A good part of the hardness or lack of hardness of bricks has to do with their makeup and the temperature it is kilned at and duration. The quality of the kilning process is important as well as the quality of how the bricks are made in their makeup. When it is that soft, the cement mortars will damage the brick glazing surface if ever pull away for any number of reasons. Another reason is actually the principle of masonry in that the mortar should not be harder than the masonry unit it is binding together. Why? If the mortar is harder, stress cracks or even settlement cracking will run through the rather more expensive masonry unit than the less expensive mortar. This is why we use lime mortar for softer masonry units like old bricks, some types of softer stone masonry units. 

Harder stone masonry units like granite, gabbro, basalt could use portland cement-based mortar but I would use a mix that contains lime mortar. There are ways to make stone masonry that is solid. When it comes to CMUs and cement/concrete bricks (yes, bricks not blocks) and possibly some types of modern hard bricks, I would use cement mortar. 

Honestly, if I have a choice, I would still soften the mortar a little bit by mixing the mortar with lime mortar but not much but enough so that any cracking would be controlled as much as reasonably can be by the cracks running through the mortar joints instead of the masonry units. 

The thing is a lot of architects, designers, and contractors don't know better or the science behind this and sadly perpetuate poor construction. There are a lot of reasons for it and no simple solution otherwise it would have been implemented a long time ago and everyone would know better but that's the sad world we live in.

Large wholesale box stores supplies what sells and makes them money but that also feeds misconceptions which also has a part in the feedback loop in the marketplace. It is like the idea that some people think hand tools like hand planes, fret saws, and other such tools are no longer used. However, those tools are still used but namely by high quality fine craftspeople versus the glorified gorillas that works as laborers in construction.

Apr 14, 21 12:04 am  · 
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