lime mortar mix.

[robgil]

its simply lime , sharp sand and water isnt it?
does anyone know the ratio's?

 

[Tom]

Well, I know what I've used for all the work on my house but no doubt someone will say it's all wrong, so I'll leave it to the experts. One will be along soon enough........

 

[Jon Maine]

3 sand, 1 lime is fairly universal, by volume, not by weight.

 

[FamilyWiggs]

3 sand, 1 lime is fairly universal, by volume, not by weight.

A very important distinction for the newbie! I remember the look on the builders merchants face when I asked him for 3 ton of sand and 1 ton of lime!

 

[biffvernon]

Given that both sand and lime are dry, just what is the important difference if weight were used instead of volume? It's too early in the morning.

(Yes, three shovels of sand and one lime will do just fine.)

 

[Tom]

Hoorah!!! At least I got something right :roll: This is exactly the mix I used, made up the day before and knocked back up prior to using. Now, there's bound to be something wrong with doing that :lol:

 

[MdB]

If you are talking hydrate rather than putty, it is significantly less dense than sand (especially wet sand). If you mix by weight then you could end up something like (i.e. I'm guessing) a 1.5:1 mix rather than a 3:1 mix.

 

[chuckey]

Use dry sand , wet sand can occupy up to 30% more volume! I use 1: 2 1/2 (or 2 :5) for sharp sand. This is what St Astiers say use for their hydraulic lime.
Frank

 

[robgil]

now the big question , would you use hydrated lime or putty?
hydrated lime i have read is inferior and ive also read its only good for use as a plasticiser for cement. :shock:

 

[biffvernon]

Hydrated is fine. Some people claim a difference in workability, like some people claim that a £100 bottle of wine tastes better than a £10 bottle. I wouldn't know.

>wet sand can occupy up to 30% more volume! You've covered yourself with the 'up to' phrase but if we are talking anywhere 30% I don't believe you. With a coarse, sharp sand I doubt there would be a measurable difference. The water fills the spaces between the grains and any film separating grains would be negligible.

>If you are talking hydrate rather than putty, it is significantly less dense than sand (especially wet sand). If you mix by weight then you could end up something like (i.e. I'm guessing) a 1.5:1 mix rather than a 3:1 mix.

Hmmm. Quartz has a density of 2.65g/cm3, Calcium hydroxide is 2.21g/cm3, Calcite is 2.71g/cm3 (yes, it gets heavier as it carbonates).
But these numbers are all about the same on the shovelfull and wheelbarrow scale of measurement. So density will depend on the entrapped air. Coarse, sharp sand (which is what you should be using) might be 25-30% air, finer sand a bit less as it packs more tightly. I guess that hydrated lime powder packs even more tightly so there is even less air.

Now, how to smuggle the kitchen scales out to the shed.

 

[MdB]

I use hydrate unless I have some left over and then I turn it into putty so it keeps.

Chemically they are the same. It has been discussed before and the comment was made that matured putty may have been better when lime came in lumps but this isn't an issue now that it comes as a fine powder. The people that disagree with this are the lime putty manufacturers...

 

[MdB]

I was going by the bag of sand (25kg I think ?) being roughly half the size of the bag of hydrate (25kg).

I would also say that there is an awful lot of air in hydrate as you can add a lot of water to it to turn it into putty and it still reduces in volume as the air bubbles out.

Let us know if you get the scales into the shed to sort this out...

 

[biffvernon]

Back from the shed.

Dry sand weighed in at a mere 1250g per litre so that means it is about half air, not the 25-30% I said earlier.
Hydrated lime powder was about 1000g per litre so has even more air, or as MdB says, 'an awful lot of air'.

Ho hum.

 

[Jon Maine]

This may interest you to

http://www.buildingconservation.com/articles/mythmix/mythmix.htm

I have always tried to keep sand covered and essentially drained and dry on site, also when using powdered lime we have used a container to gauge and then gently pack it as it does fluff up.

 

[robgil]

i was reading that last night jon , couldn't make head nor tale of it. i shall try again when not tired and sober.

so , hydrate is fine , 3 to 1 mix with sharp (preferably unwashed?) sand.

do i need to mix it today then re-mix it and use the next? or is that just with putty?

 

[MdB]

That is in interesting article Jon. They sound like they know a lot more than me (which isn't difficult). I guess most of my mixes have been 2:1 sharp sand to hydrate to take into account the air in the hydrate but it does look like I should be putting even more lime in.

This bit is interesting:

Non-hydraulic and hydraulic limes are both available today as dry hydrates. The former, as ‘high-calcium’ lime (generally marked ‘CL90’ to indicate that it contains 90 cent calcium lime), is usually marketed as builder’s lime, and is primarily intended as a plasticiser in cement:lime:sand mortars (1:1:4 or 1:1:6 for example) for modern masonry construction. This processed lime is not, however, a good substitute for traditional non-hydraulic lime putty or for use on traditionally constructed buildings as it does not possess the same working characteristics as traditionally slaked non-hydraulic lime putty. It is not intended for lime:sand mortars and cannot be relied on to meet the strength and durability performances required.

I wonder what they mean by working characteristics as I've not noticed any difference between expensive putty and cheap hydrate when using them.

 

[Jon Maine]

i was reading that last night jon , couldn't make head nor tale of it. i shall try again when not tired and sober.

so , hydrate is fine , 3 to 1 mix with sharp (preferably unwashed?) sand.

do i need to mix it today then re-mix it and use the next? or is that just with putty?

I don't usually use hydrate but as I understand it if you knock it up and leave it a day or two it will improve workability the same as other lime mortars.

Personally in exposed external conditions I would use hydraulic. As much as anything because it is easier to tend to before it sets and less prone to failure because of this.

 

[Louis Henry]

I always mix up hydrate as long as possible before using it. After a couple of months it is wonderfully sticky. If only I could control the amount of moisture in the sand, it makes the mix vary from soup to cheesecake. Years ago the lime was slaked on site and the sand was from wherever was closest so although I am sure a 3:1 ratio using sharp sand is best, it really isn't that critical.

 

[MdB]

From Jon's article, which sounds authoritative, 2:1 or 1.5:1 would be better.

 

[Jon Maine]

From Jon's article, which sounds authoritative, 2:1 or 1.5:1 would be better.

We have always used hydraulic on a 3 - 1 basis by volume slightly compressing the lime so its not so fluffy and air filled with lasting results, Much the same for putty lime work too. Top coat plaster may drop down to 1.5 to 2 to 1 but that was the only thing.

As for hydrated never been an avid user so have no experience.