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Hydrated Lime in render? |
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| message from -= debully =- on 13 May 2004 |
Can anyone give a precise reason why Hydrated Lime is used in exterior
rendering?
Been told to use a 4sand / 1 cement / 1 HL mix, but never come accross HL
before.
Rgrds,
debully
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| The Natural Philosopher replied to -= debully =- on 13 May 2004 |
At a guess, its to make the mixture less brittle and less prone to cracking.
I did a lot of bricklaying with a 1:1:6 white cement/hydrated lime/sand
mix. Nice to work with too.
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| N. Thornton replied to -= debully =- on 13 May 2004 |
When cracks form in render the lime reacts with CO2 in the air to grow
a new crystal across the crack, thus rebonding it. Consequently
suitable mixes with lime are much more crack resistant than cement
alone, which has no such mechanism.
HL is sold in bags as 'lime' at any BM.
Regards, NT
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| Michael Mcneil replied to N. Thornton on 14 May 2004 |
"N. Thornton" <bigcat@meeow.co.uk> wrote in message
news:a7076635.0405131645.4fd1efc7@posting.google.com
Lime is calcium oxide and hydrated lime is calcium hydroxide. If you
could get hold of lime it would heat up when used. I think that is why
in the good old days the stuff was mixed days in advance -no cement
being used in the mix. But that was even before my time.
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| Anna Kettle replied to Michael Mcneil on 15 May 2004 |
In a cement render, hydrated lime is there as a plasticiser.
You are talking here about lime mortar where the lime itself sets. A
lime mortar contains lime and sand and NO cement. As soon as cement is
added, its gets in the way of the lime set so although what you say is
true, it is not relevant in this case.
Anna
~~ Anna Kettle, Suffolk, England
|""""| ~ Plaster conservation and lime plaster repair
/ ^^ \ // Freehand modelling in lime: overmantels, pargeting etc
|____| www.kettlenet.co.uk 01359 230642
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Archived message: Hydrated Lime in render? (UK DIY Home Repairs)
