Note: Back when I built my house, I was, so far as I could find, only the second person in the Calgary area to have Concrete Countertops. Now they are all the rage in upscale houses. So ... as you read this, be kind, it was written back in the last millenium when it really was something special to have concrete countertops.
One of the unique aspects of the house is the concrete countertops. These add a very solid, rustic and obviously unique character to the house.
The most common question I'm asked when people view the house is "What are THESE made of? They are VERY solid."
The countertops are made out of 1.5" thick, high strength, gray concrete with 3/8" inch rebar along all the edges and every 1 for width. Most are 2' wide so they have one rebar along each edge and one running down the middle. There is also rebar every aprox. foot going at almost 90 degrees to the edges.
Actually, it isn't exactly 90 degrees because I cut them too long (about 22") and found they moved too much when pouring started, so I put them on a slight angle so they wouldn't accidently come sticking out.
Home depot (my source of concrete) supplied 2 strengths, I decided to take the stronger just to be safe.
After pouring I kept it damp for the first 12 hours (by sprinkling) and then wet for the next 21 days. I didn't want ANY cracks. This was easy to do because I cast them in 6 mil plastic so I could keep a puddle of water on the top (which became the bottom) for the full 21 days.
After over 10 years I still do not have even 1 crack.
To prepare for pouring, I laid down forms first, then I laid down the plastic. by keeping the plastic a little tight, I was able to get nice rounded edges. Remember that the TOP starts out at the BOTTOM when pouring. The "Top" when pouring becomes the "Bottom" when installed.
The corners are slightly mangled (the plastic wrinkles.)
One well meaning friend told me it would be easy to do because the concrete would "push" the plastic into position. Fortunately I knew better, and it became very obvious when pouring that the concrete would NOT push the plastic into shape. Anywhere I did not get the plastic perfect, the concrete had a ripple.
I choose NOT to rent a vibrator. I concluded that "Since I'm going to be painting them and putting a thick clear epoxy coat on anyway, I don't need to get a really smooth top surface"
I should have rented a vibrator. And there are 2 reasons why:
Reason number 1. It was a pain to fix up. I had planned on using concrete crack filler, and it did work. But sanding (using a angle grinder with a concrete pad) made a big mess that took days to clean up. We were living in the house by the time I did it. We couldn't apply the crack filler to the pits until a month or so after the countertops were poured, and then we waited a couple months for it to harden before sanding it. When I tried to sand it when it was fresh (a week or so old), the angle grinder cut into it like butter. When I left it for 2 or 3 months I was able to get a better finish. Oh - and the crack filler shrank so I had to apply many coats to get all the pits removed. WHAT A PAIN!
Reason number 2. The BIG reason.
When I poured the countertops, I, by hand, vibrated as much as I could "to get it as smooth as possible" Well! I turned out that for over 3/4's of it, I did a really good job. The finish was glassine. (sp? Looked like glass) The rest was dull or pitted (where the cement didn't get down around and under the aggregate)
The sad part is that my wife and I both REALLY liked the areas where the concret had the glassine finish. It was easy to clean, we could set hot pots down on it without damaging it, and friends who visited agreed that, where it was glassine, it looked fantastic.
We would have stopped right there and had very attractive gray countertops. Yes I know, it doesn't sound attractive - but it really was.
So my big advice for you is, even if you (like I did) think that the gray will be ugly - try to get a perfect surface by vibrating when you pour. Even if you don't like it, it will at least make the next step easier.
We did end up with an extremely attractive finish. It is, admittedly, nicer than the gray. (Even though, had I done the gray properly, it wouldn't have been worth the extra work/problems to get the final finish.)
The #1 problem with finishing is: Once you put any finish on, you will no longer be able to put hot pots right off the burner on it. They will ruin the finish. I know, I tested. No not a mistake, I tested on purpose - in an appropriate place of course.
So, a finish will make your countertops prettier, but they will decrease their utility. So... do them right and leave them gray!
But if you must... Here is how we did it (yes, Madman's wife helped at this point.) We had the countertops match the chair rail that we had done previously, so it picked up on the theme and carried it from the dining room to the kitchen.
Step 1: (Both) Wait 4+ months for everything to harden properly. I'm told 3 months would have been enough. I waited 6 due to "other priorities."
Step 2: (Me) Clean the concrete with Muriatic Acid according to manufacturers instructions. Nasty stuff this - have lots of ventilation and wear gloves etc.., Don't spill any anywhere or you'll be sorry! (No I didn't spill any, but I tested. I put many many layers of newspaper down around to catch the inevitable drips. - and remember the drips will splash so cover for a long way around.
Step 3: (Me) We painted the countertops with a medium pink/maroon stained concrete paint. This was the base coat.
Step 4: (Me) We again painted with the same color to make sure no gray was showing.
Step 5: (Jan) Sponge painted with a darkish blue. Leaving plenty of the pink showing through. Probably 30%.
Step 6: (Jan) Feather dusted a dark maroon pink. Leaving most of the pink & blue showing through.
Wow! At this point they look FAN-TAS- TIC
Step 7: (Jan & Peter) The 1st epoxy coat. About 3/16" thick. We followed the directions on the can, but it was VERY runny and dripped for hours, but the finish was good. We do have a few "bubbles" We made the mistake of starting at 10:00 at night (I go to bed at 2:00 usually.) At 3:00 I was still trying to "breath out" the bubbles (the carbon dioxide makes them pop) The big problem was that my eyes were too blurry and the light was not sufficient to find them.
Next time, I'm starting at 6:00 AM in the summer (lots of light, long hours of light) and only doing 1 counter top at a time.
Reflections (pun intended) on another countertop I saw. When I started this project I made a trip to another house where someone had done the same thing. I can't find his web site anymore (he moved it and I haven't refound it or it isn't on anymore. Let me know if you know where it is so I can link to it.) He had done a gloss black paint with the epoxy coating. Every finger print, wipe of the cloth, spec of dirt shows up very easily. He mentioned this as HIS mistake<g>. Going with the random pattern above got rid of that completely and we were able to keep the gloss finish without the problems of having everything show up.
So. I would NOT go with a solid color. If you are going to "finish" the concrete Have some fun with it.
Would I do it again?
Yup! I like the counter tops. They look good, They have a rustic look mixed with a very modern, very clean, very bright look. They are solid. And everyone with one exception seems to really like them.