Steam curing of papercrete will speed the chemical curing process of the cement (or the lime), but it will not do much to help the drying time of the papercrete. Since the papercrete will retain dampness more than long enough for the cement or lime to cure as it dries naturally, I don't see the point in expending the energy and effort to steam cure. That said, I have never tried steam curing and maybe it will do something different than what I expect.
If you decide to steam cure some papercrete, please cast some papercrete from an identical mix and let a small sample cure naturally without steam curing side by side. Once both samples are dry, please compare them and report your results to the rest of us.
Spaceman is correct. I have conducted some home relative calorimeter tests on compressed vs uncompressed papercrete. He reported correctly that my experiments indicate more densely packed papercrete produces a better insulation material per inch. The amount of improvement depends on many factors. Greater compression yields better insulation, but there is a point of diminishing returns. The higher the ratio of paper in the mix the higher the R-Value and the more compression will tend to improve that R-Value. The greater the mineral content of the mix, the worse the R-Value and the less helpful compression is in improving the R-Value.
The ratio of paper to mineral content is a balancing act. Higher mineral content is required to inhibit flamability and smolderability. It also improves compressive strength. Lower mineral content produces the best insulation. As with most things, finding the happy zone between the extremes is the best course. I never recommend installing combustable or smolderable papercrete.
For ceiling tiles, I see zero benefit in adding any sand to a papercrete mix. I suggest sticking with simply paper, cement and/or lime as spaceman suggested to get a nice white color, and borates.
I see no problem compressing a stack of ceiling tiles together, if you were to put some kind of seperator between each tile. Stack them up and give them the big squeeze. Perhaps a screen or a bamboo mat that will yield an attractive pattern would be good seperators. It would be helpful to unstack them after compression. This will speed the drying process very dramatically.
I also suggest casting your panels slightly larger than is required. After they are completely dry, (and done shrinking) you can cut them to the exact size required on a table saw. You will probably be a lot happier with how they fit into the grid when you can get accurate sizing. As long as the sand is left out of the mix, you should be able to cut the papercrete just like wood without damaging your saw blades.
Building a homemade panel cutter jig for your table saw would speed the process dramatically. Here is a website describing how to build a panel cutter for a table saw:
http://www.cabinetmaking.com/pages/panelcutter.htm
Hope this helps.
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