My reference to natural cement in this instance is not relevant to if it 
was actually the material used at that time in Australia. David's 
question was what to do about matching a Portland cement with 'other' 
properties (more specific, what is being done in the USA about matching 
the properties of older Portland cements, short of raiding Thomas 
Edisons chemistry lab and seeing if there is an unlabeled barrel 
available), though the assumed properties remain obscure... to whit I 
suggest looking at the properties of natural cement and see if they more 
aptly suit the need which appears to be both physical and political.

My crude understanding, not enough cofee not enough sleep during the 
lecture, is that the natural cement is somewhat more elastic than 
contemporary Portland. I suppose that if one were to identify the 
properties that one wants to mimic that a Portland cement chemist would 
be able to come up with something.

As to problems w/ the lime/Portland mixes I will be curious to learn 
more. I am on the receiving end of design specifications and if the 
architect tells us to use a 1:2:9 mix we assume they know what they want 
and why.

][<en

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