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 -- **Please remember to trim posts, as requested in the Terms of Service** To terminate puerile preservation prattling among pals and the uncoffee-ed, or to change your settings, go to: <http://listserv.icors.org/archives/bullamanka-pinheads.html>