On 4/22/2010 12:28 AM, David West wrote:
>
> We are currently preparing to lift and relay a 19thC encaustic tile floor.
>
> It was originally laid onto a sand/cement bed supported by timber 
> floor joists.  The floor structure is currently being stiffened prior 
> to commencement of the tiling repairs.
>
> The heritage architect has found documentary evidence showing that the 
> sand/cement bed was based on a 1:3 portland cement : sand mix, which 
> he is keen for us to reproduce.
>
> The key issue here is that 1890s Portland cement was very different to 
> contemporary Portland cement, and therefore we are searching for an 
> appropriate substitute mix that will give us similar physical 
> properties to the original mix.
>
> My question to this list is:
>
> What is the current preferred approach in the US to reproducing the 
> physical characteristics of a late 19thC 1:3 portland cement : sand 
> mortar given the difference in properties of contemporary Portland cement?
>
> Look forward to your responses ...
>
David,

Depends on the properties you intend to mimic but may I suggest 
Rosendale natural cement? There are several ppl on this list that can 
help you w/ that. If they don't speak up let me know.

In general though the solution is to add hydrated lime, say 1:2:9 as I 
was asked to do just this week in a temporary patch to brickwork of a 
similar 19th c timeframe... w/ the understanding that later down the 
line the entire plaza would be specified to be reset w/ Rosendale.

Ken

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