Im rechinking an old log church .Ive done acres of chinking before with everything from river sand to mud but this is first time ive ver used white portland .My mix has been 2 parts portland/1 part hydrated lime and 3 parts yellow(but called white) sand.
It was in the low 50’s a bit cloudy .Most chunking is being done on stapled diamond stucco lathe with some fiberglass backer in deep areas.Some is being done on old chinking which was pure portland and couldnt be removed without boogering up chinking inside.I used the concrete/concrete additive on those areas.
Problem is that a bunch of fine cracks appeared in the not yet hardened chinks.Ive had this happened on chinking over chinking where mositure is sucked out of the overlay but these cracks were in just plain mortar/lather areas.It wasnt drying to fast due to hot sun /dry logs altho it was somewhat windy.
I think it mite be something with my mix as ive never used the white portland before.The hydrated lime says Hi Calcium. Could mix be too rich? too poor? Kill the lime? I usually use a mortar mix which of course is almost 50/50 portland/lime.
Any suggestions?
Replies
i'd think more lime... maybe use a garden sprayer to wet the area before you apply it... I don't know chink about chiinking... but i've played with alot of lime mortar... the white portland wouldn't be an issue... sounds like the moisture is being sucked out of the mix...
just guess'n
p
don't have any advice specific to your mix - however, I could suggest fiber plaster as part of the recipe - helps the mix to hang together and stick - I do recognize there are many acceptable ways of doing the job -
the other thing I don't see mentioned is wetting the logs/chinking before you daub - dry wood/masonry will suck the moisture right out of your mix, with attendant problems -
A similar thing happens when you stucco against unpainted stucco trim.
Sealing the wood first prevent moisture from swelling the wood when wet. Unsealed wood shrinks back from the cement after both drys.
Seams like your mix would have to be way off
for it to fail before it even set up.
Two maybe's-
That wind can dry things quickly. I doubt it but
could happen.
I'm guessing you have enough experience to know better
but overly wet mud put on to thick can slump and cause cracks while it's still
wet.
Edited 10/31/2008 8:04 am ET by Henley
Twas the lime ! I figured it might be too rich.Cut it out completly and not a single crack .
Cool.
Time to chink!
Have you thought of putting some concrete additive in your mix? I've done high end masonry with rocks that were placed in a way where the mortar had to be very strong and we used lots of the glue additive.
You do have to be carefull with it though. It is hard to clean if you're messy.
my understanding is more calcium will make cement set faster. maybe the mix itself is curing too fast.