Onoff
In the land of the unfinished project I am King!
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- Sevenoaks, UK
Yuo need a jack for all that.
A jack?
Yuo need a jack for all that.
A jack?
My plastering guy. Jack.
That looks like a very interesting article from the abstract (I'll see if I can get it through the library or get work to stump up the $40). A good find.Explain to me, chemically, the difference between hydrated lime "bag lime" if you will, that has as you mentioned been soaked in an excess of water for the timeframes you mention and fat lime bought specifically for the purpose...
All very sensible and I couldn't agree more. I'm not suggesting using random aged, part used bags of hydrated lime. I'm fortunate in that I can get bags from newly ordered pallets that either get used in a mix straight up, for rough building and pointing, or put into a drum with excess water for later use as a base for basic plaster or as limewash.That looks like a very interesting article from the abstract (I'll see if I can get it through the library or get work to stump up the $40). A good find.
15 years is a long time for maturation. I don't know what changes that would have compared to the minimum 6 months that lime putty is aged for in the UK.
As I said above, chemically similar but functionally different. Some figures from Rose of Jericho about excess and scantness of water when slaking here.
The fabulous "Mortars, Renders and Plasters" from the English Heritage Practical Building Conservation series has the following: "Slaked lime can be in the form of a powder or a putty. Both are chemically identical, but the powder is made using the minimum amount of water required to hydrate the quicklime to powder, whereas lime putty is slaked in an excess of water, resulting in a sticky wet paste." In this sense, freshness of powdered lime is fundamental. "The problem is particularly acute in hydraulic quicklimes, where even a small amount of 'air slaking' can result in a large reduction in strength of the material. Many historical texts refer to the uselessness of air slaked lime for mortar making, and advise that quicklime should be always used fresh." In the same way, powdered slaked lime begins carbonating on creation, while lime putty in an excess of water does not.
"...non-hydraulic lime made from chalk or limestone...in conservation circles is popularly called lime putty, the form in which it is most commonly used. In powder form, builder's merchants use the term 'hydrated lime'. This causes a great deal of cunfusion, since all lime, whether putty or powder, is hydrated."
"Non-hydraulic lime putty can be stored indefinitely, providing it is in a pit or impermbeable container fully protected from direct contact with air and frost. In fact, its qualities improve with long maturing. All powdered binders are sensitive to dampness, so they should be stored dry. They can also absorb moisture from the atmosphere, and partially carbonate or set. When this happens, the powder will feel gritty when rubbed between the hands, or there will be lumps of harder material amongst the powder. In such cases, the binder should not be used. All damaged bags should be rejected. Once a bag is opened, the top should be sealed by folding down and weighting with a stone or brick; the remaining material should be used within two days of opening. Any material not used within this time should be discarded. Unopened bags of powdered binders have a limited shelf life of up to six months, and should not be used beyond this period."
At bottom, the objective with lime is to obtain a bonding agent that is less strong and more flexible than the materials it is bonding. Excess strength in cement causes the majority of masonry problems which was recognised as far back as the introduction of Portland cement in the 1930s, and quickly latched onto by conservation specialists. However, a bag of indeterminately old powdered lime could well create a mortar with no bonding strength at all, which would be contrary to the requirements from any standards body!