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mortar for limestone blocks

Stone Conversations : Archive 7 : Message 00536

From: John Twilley <jtwilley@zzzzzzzzzzz>
Date: Fri, 10 Dec 2004 22:26:35 -0500
Subject: mortar for limestone blocks

The process of by which the lime component of a lime-based mortar sets
involves carbonation by carbon dioxide in the air. This requires moisture to
occur and it happens from the outside inward. The pre-mature drying of lime
mortar will cause shrinkage cracks to develop at a time when it has very
little strength. Air circulation is required as well (lime mortar will not
set under water where carbon dioxide is excluded. That's why it could be kept
in a lime pit after slaking for long periods.) Masonry mortars that include
both a hydraulic component, like p.c., and lime will take an initial set from
the reaction of the hydraulic component with water. That gives them some
early strength and makes them more resistant to cracking. But unless the lime
gets a chance to cure under damp conditions with air circulation, the intended
final strength will not be reached.

John

Marcus wrote:

Quoted text begins.Ahhh, I get it. But why exactly is it so critical that the mortar not dry
out too fast? And how critical is all this for regular Type N?
End of quote.


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