[Strawbale] Chemistry and physics of initial lime curing

[Derek Roff]

It's great to see Harry posting again.  I hope he and Beel will offer their 
knowledge and experience on what happens in lime plaster/render during the 
first hours, days and weeks after it is applied to a wall.  I've just come 
from the European Straw Bale Building Conference, where some very 
experienced lime plasterers said that lime plaster stiffens and hardens on 
the wall during the first few days after application, due exclusively to 
re-carbonation.  Based on what I have read previously, I think this is 
incorrect.  But I hesitate to contradict people who have hundreds of times 
my experience.  One needn't know anything about chemistry and physics to 
apply plaster skillfully, but I would like to understand these details.

I'm thinking that the initial curing of applied lime plaster is complex and 
dynamic during the first hours and days.  If one applies a 3/4" thick layer 
of plaster, as mentioned in a recent posting, I imagine that the curing 
begins at the exterior surface, where there is contact with the air.  And 
to a lesser extent, at the plaster/straw interface, where some oxygen and 
drying potential also exist.  Over a few days, the plaster gets stiffer and 
harder.  Why?  And how does this hardening proceed from the surface to the 
interior of the plaster layer?  What is going on at the chemistry and 
physics levels, and how does this affect the practitioner?

I will be grateful for any insights that our lime experts can offer.

Thanks,

derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu