Anyone had any success filling voids in the top surface of a concrete counter-top? I find that a thin slurry of cement forms a skin over the void when I try to squeegee it into the voids. The air won’t leave the void(the smaller they are, the more vexing) and hence, the slurry won’t enter. Any secrets?
thanks, eric
Replies
While I haven't had much trouble with that I seem to have read the suggestion of using a grout for that purpose. Did you cast it upside down?
PaulB, Yes, cast upside down in melamine form. Sometimes I get lots of tiny(1/8" dia.) voids which are buggers to fill.
eric
hmmm. well I'm sure no expert but that seems odd... Are you vibrating it? There's a great Taunton book on councrete countertops. I'm sure others here have more experience than me, I've only made two but never had that problem... wish I could help more.
Step in, Mongo, and tell him how to use an old 1/4HP motor with an eccentric weight on the shaft, mounted to the table supporting the form, to vibrate it sufficiently to drive out all the bubbles.
A slurry paste, made with cement and the same sand as your mix, tinted with the same colorant, can be used to fill the voids.
Depending on the size I used a RO sander held against the form in various spots or my Sawzall shoe to vibrate it... seemed to work well in my limited experience.
I share your pain. No matter how much you vibrate the mix in the form, there will always be those small vexing air bubbles. Even if you suceed in getting them off the surface of the melamine form, some will rise only slightly and be exposed with subsequent grinding/polishing. I have been most successful in using only cement mixed with colorant and a concrete water reducing agent with a little water. I keep the paste really dry and rub it in using a small rag. I dust on more dry mix as I need it. If it's too dry, use a spray bottle to add a slight amount of water. This is a job that requires a lot of elbow grease.
After all that, I figure the resulting small pin holes will not matter.
Oh yea,,,,,for the bigger voids (if you have any) I use the same paste, only I mix in a little sand. You can actually push individual sand grains into some of the voids. Don't try to use sand with the really small ones, it simply will bugger up the work.
jpatrick, What I really needed was someone to reassure me that I wasn't alone in finding this situation puzzling. I like your suggestions and intend to try them tonite. I've tried going the other way(wet surface and wet mix) and found that unsatisfactory.
Thanks for weighing in.
eric
on the topic of concrete vibration...
has anyone seen this...
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90304
View Image
its a hand held concrete vibrator.... no sure how well it works, but its a little cheaper ($39.99) than the shaft types...
You might try using a little "thinset" like you set tile with... tinted to match (trial & error till you get it). It is much finer grains of sand and should trowl out pretty slick.