Hydrated Lime?

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Originally Posted by Dop

Just as an aside, I believe the Romans also used volcanic ash in their concrete, apparently that is much better than the additives we use today?

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While not the first, Romans were the first to widely use a cement made by adding pozzolan to the hydrated lime in their mortar, converting it into a 'hydraulic cement' similar to the modern 'Portland Cement' familiar to us today.

The pozzolan used by the Romans (and today where available) is a naturally occurring volcanic ash, which is in some ways better than what is mostly used because the grains are highly porous, giving a very high surface area and hence highly reactive without being extremely fine grained.

The chemical reaction is basically the same as with modern cements, where the 'pozzolan' component results from the incorporation of siliceous material with the limestone before it is heated. This results in a 'clinker', that is then ground to make the cement. The material used by the Romans did not require the crushing before heating or the grinding afterwards - just needed to be mixed with hydrated lime immediately before use, so a lot less messing about. But there is no significant difference in the final product, or perhaps more accurately, the difference between batches (either type) is more than the difference between the ancient and modern.

John

My brother is a horticulturist and says you mix lime into clay. It breaks the clay down into usable soil.

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Originally Posted by 350RRC

Yep you fully hydrate it overnight.



People may not realise that the Whitehouse in DC is actually lime washed.



DL

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Well after a bit of a fire during a scuffle decades ago it needed it [emoji6]

An unexpectedly interesting thread...

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Originally Posted by 350RRC

You can slake it, mix in concrete colour and limewash any building in virtually any colour.

I've done this on some serious heritage buildings.

Lasts as long as paint and lets the walls breathe.

Have used it over a modern product that sticks to anything, even glass.

DL

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How do you apply it and have you ever tried spraying it on?
Do you need to keep it stirred in order to stop the putty from settling out?
I saw some very nicely lime washed buildings at Port Arthur at Christmas and was going to try and find someone to talk to about them but couldn't find anyone who knew their process.

Regards,

Tote

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Originally Posted by Tombie

Well after a bit of a fire during a scuffle decades ago it needed it [emoji6]

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Pretty sure it gets done every year.

White is a shocker for picking up dirt, especially in a city.. The repeat coats are very thin, get thinking of'paint' the consistency of milk and you get the idea.

Cheers, DL

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Originally Posted by Tote

How do you apply it and have you ever tried spraying it on?
Do you need to keep it stirred in order to stop the putty from settling out?
I saw some very nicely lime washed buildings at Port Arthur at Christmas and was going to try and find someone to talk to about them but couldn't find anyone who knew their process.

Regards,

Tote

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Hi Tote,

PM me some contact details and I'll send some pics which you are welcome to post.

Quite easy to do, incredibly quick once you get your head around it.

And it just occurred to me that you could probably do a whole house in a day for $50 including colour once the prep has been done and one coat has been on.

Cheers, DL

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Originally Posted by 350RRC

Pretty sure it gets done every year.

White is a shocker for picking up dirt, especially in a city.. The repeat coats are very thin, get thinking of'paint' the consistency of milk and you get the idea.

Cheers, DL

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Was painted in Lead Based White paint in 1818 so hasn't been lime washed since..

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Originally Posted by JDNSW

While not the first, Romans were the first to widely use a cement made by adding pozzolan to the hydrated lime in their mortar, converting it into a 'hydraulic cement' similar to the modern 'Portland Cement' familiar to us today.

The pozzolan used by the Romans (and today where available) is a naturally occurring volcanic ash, which is in some ways better than what is mostly used because the grains are highly porous, giving a very high surface area and hence highly reactive without being extremely fine grained.

The chemical reaction is basically the same as with modern cements, where the 'pozzolan' component results from the incorporation of siliceous material with the limestone before it is heated. This results in a 'clinker', that is then ground to make the cement. The material used by the Romans did not require the crushing before heating or the grinding afterwards - just needed to be mixed with hydrated lime immediately before use, so a lot less messing about. But there is no significant difference in the final product, or perhaps more accurately, the difference between batches (either type) is more than the difference between the ancient and modern.

John

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Pozzolan was one of the additives we used when mixing the cement to build the hull of our Ferro Cement yacht in PNG back in the 70,s.
Supposed to help make it watertight.
Must have worked as it did not sink:D

Keith

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Originally Posted by 123rover50

Pozzolan was one of the additives we used when mixing the cement to build the hull of our Ferro Cement yacht in PNG back in the 70,s.
Supposed to help make it watertight.
Must have worked as it did not sink:D

Keith

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Most modern concrete mixes include pozzolanics, often fly ash from industrial processes, as well as coal fired power stations. Any old farts will remember the blue and white trucks with pressure tankers running the highway's under the name of Pozzolanic Transport, used to cart cement powder and fly ash all over the place. Still happens, but different companies nowadays.
For the more environmentally aware amongst us, lime mortar actually absorbs all the CO2 that it produced during the slaking, when it sets. You can also very easily recycle bricks with lime mortar attached, unlike cement mortar.