I decided to take pictures all along the way to document my effort. There are far better concrete counter top tutorials out there. This is simply to remember what I did, and maybe didn't do along the way.
Here we go!
To make the mold, you need a sturdy, level table. I took a couple of saw horses as the base of my table, with 8 ft long 2x4s hold up two 3/4" sheets of particle board. The mold material is melamine (MDF with melamine on either side).
I had the lumber yard where I bought the melamine rip 2" strips the length of the board, for me to make the sides of my mold with.
Once the caulking is done and allowed to cure overnight, it's time to prepare the reinforcement. The guides and books I've read say you should use rebar, but it seemed like overkill - so I just used remesh, and made sure that there was good clearance around the edges. The reason for hanging it like this is to keep it from being too close to the top. This is important because if it's too close to the top, it can create an issue called 'ghosting'.
All ready to pour concrete now!
Concrete starts to set in about 30 minutes - so I didn't take time to take pictures of me mixing it and putting it into the mold. It was pretty hectic getting this part done. I didn't prepare enough concrete to mix. I'd say I had 95% of what I needed, so I had to improvise. I cut a couple of pieces of melamine and pushed them down into the concrete to get it to fill out the rest of the mold.
Doing this has the potential to cause several really bad things to the final product - pushing the remesh all the way down to the bottom of the mold (the top of your countertop) being the biggest. I had to wait and see.
I let the concrete cure overnight, and even though everyone says you're supposed to wait three full days before you do anything, I decided to see how it turned out. I removed the sides of the mold, and cleaned up all of the mess created from the initial pour.
So far so good!
I carefully flipped it over (this piece weighs around 180 lbs) and placed styrofoam underneath it to make sure I didn't do any damage to the corners.
The sides were pretty clean and free of air bubbles and voids for the most part. One corner didn't turn out so well, but that's OK, because it's on the bottom of the countertop in a corner that won't be visible.
Above is a close up of what will be the back of the counter top, that will go against the wall.
This is a close up of what will be the outside corner of the front edge of the counter top.
The concrete will be ground down to show the aggregate, and then polished. During the polishing, a slurry is used on all of the remaining air bubble voids.
This is the counter top ground and polished. There's a lot of aggregate showing here, and even though it looks somewhat rough, it is as smooth as glass. There are a few voids that I'll have to patch on the top of the surface, but for the most part, it's ready to go, with one small 'issue' that I have yet to figure out how to fix...
I have to figure out how to get a completely consistent grind / polish over the entire surface. Never having used a grinder / polisher before, it's tricky. The concrete is still a bit damp, but you can see the pattern that the grinder was ran over the slab if you click on the bigger picture...
I did a bunch more grinding and polishing on the slab. I went in smaller circles, rather than back and forth. I think that I have some ghosting after all, but it seems fairly minor. I think that we'll just deal with it, as it looks really good otherwise. (after the fact - that was just me doing a very poor grinding / polishing job!)
I finished polishing the first piece, soaked in a sealer, and started to wax and polish it. It became rapidly clear to me that I don't know the first thing about waxing and polishing. I did a really lousy job, and may need to strip the wax off and start over. But, this is what I've got so far...
I moved the first piece outside to make room to start in on the next piece. I am keeping it covered, so it's out of direct sunlight, and will finish curing for two to three weeks.
By then, I'll hopefully have figured out how to do the whole 'wax and polish' thing, and can re-do the lousy job I did. I think I'll add a picture tomorrow showing what it looks like in sunlight.
Time to start in on more pieces of the countertop!
There are four more total, and I was able to fit three onto one piece of melamine. This is very helpful, as it will make grinding and polishing to a consistent level easier for these parts. I'll have to figure out how to integrate the last piece of this run so it all looks like one big piece once it has been put in place.
I decided to go with four smaller pieces so that it would be easier to move them around. As they currently are, I can flip the biggest piece over by myself. If I were to have consolidated into two, or even three pieces, I don't think that I'd be able to handle them on my own.
400 pounds of concrete! Unlike last time, I wasn't just a bit short, I had quite a bit left over. The two extra sections (compared to the mold picture above this one) are just the leftovers. I made a small piece to grind and polish up as a sample piece for when we go to pick out flooring and backsplash tile.There's one last piece to pour, and were it in this picture, it would be on the near side of the closest piece (with the sink void). Once I get these ground and polished, I'll make the last piece, then match it up to the others, so it's as close to perfectly level and even as possible.
Here's a close up of the sink and knockouts for the faucet and dishwasher vent. I initially made the mistake of putting them on the wrong side. Had I not caught that, it would have left them in front of the sink - somewhat impractical!
The two far pieces have remesh for reinforcement, and this piece has 3/8" rebar.
The next day I de-molded the pieces. I spent a good amount of time with a rough stone on the bottom of each piece, to smooth them out as much as possible. The reason for this is to make sure that they're as even as possible.
As you can see, the pieces don't match up perfectly. It looks like my table is very slightly out of level, but that's not a big problem. I will fix this when I grind and polish these pieces.
Here it is after grinding. There is a bit of fine tuning that I'll need to do, but for the most part, things are much more even throughout. There's a LOT more aggregate showing through in this batch of concrete than on the first piece.
Here's a close up of one of the seams. I'll fix this by grinding them so that they're flush with each other on the top. It looks as if there's a fair amount of patching work to do, but the grinding and polishing process will wear through a lot of the 'issues' that are currently there.
Same seam after grinding.
I finished up what grinding and polishing I could, and moved on to the last mold. I have to finish this, then put all of them back together, so I can grind and polish them to be completely even with the neighbor piece(s).
This has been taped and caulked, in an hour or so I'll go remove the masking tape from the caulk seams. I have covered the tops of the sides to prevent concrete from getting into the screw heads. Dry concrete in a screw head would make it VERY difficult to de-mold.
I use black silicone caulk, so it's easy to see against the white melamine.
So I poured what I thought was my last piece. Then, I realized something was wrong (only after fully grinding and polishing the piece). So, uh, pretend you didn't see see the above picture. THIS is the last piece. Honest.
This is a sample piece I made for Claire and I to use while shopping for paint colors, flooring, and tile. I didn't do much to it, I did a quick grind and polish.
I picked up a Festool ETS 150/5 orbital sander. Oh man, this thing is nice. There are actually some pads that they make that I can do fine polishing for my concrete. That's the good news. Bad news? I have to go polish all of my other pieces again.
Here's the first piece temporarily installed to test how well it fits. Unfortunately, the previous owner decided to take a BIG chunk out of the molding for the laminate backsplash. SO ANNOYING.
As you can see, I will need to even out the bottom of this before it goes in permanently. Sadly, ALL of my pieces are like this. That's what I get for letting my table get even slightly out of level. Oh well, I've got a couple of weeks to fix all of the pieces.
There's a window behind where this is supposed to fit, so I intentionally didn't have the countertop go back as far as the original. I wanted to be able to replace the hideous window, so I needed to leave room for something new. This is just to make sure the notch I made fits into the space as intended. Good on the left side!
Looks good on the right side as well. Now we just have to figure out what to do about the molding. I still can't believe the previous owner did that, rather than just making the laminate backsplash flush to the right side of the molding. Oh well... any tips on what to do with this would be helpful!
After much work, three of the last four pieces are finally finished!
I had to grind the bottoms of each piece to make sure that they were all on even footing. After that, I had to even them out as best as I could (again, due to the slightly out of level table). Much polishing later, I sealed them, and put on a single coat of wax.
If you zoom in you can see that the pieces should all lay completely flat now, and they have a nice shine to them. Now to finish up the last piece (it needs to polished up, sealed, and waxed).
Next weekend we install them!
And the end result is:
After installing the first pieces, we had the plumber hook up the faucet and garbage disposal. The next day, as I was starting to figure out what I was going to do with my failed first attempt, I went to lay a piece of non-corrogated cardboard down to make a template. And what did I see? The BIGGEST SPIDER I've ever seen outside of a controlled environment. Spiderzilla, I'm tellin ya. Now, normally, I'm down with spiders, they eat bugs and the like. But this guy? Yeah, he's dead. Spiders that big set off that little voice in the back of your head, you know.
So there were a couple of issues that lead to issues that could not be addressed with the concrete. Primarily was that I suck at measuring. Seriously, I'm retarded. Beyond that, the walls were farther out of square than you could see with the old counter tops in place. So, I laid down a piece of non-corrugated cardboard, and cut it to the exact dimensions that I wanted the counter tops to be this next (and my last) try. Later that evening, after having purchased more melamine for to make another set of molds, I got down to cutting the sides of the mold to fit a bit more exactly this time around. The Festool saw was SUPER handy for the sink knockout, as I just made what amounted to an elongated octagon for the opening.
I made a template and the day after, after coming home a bit early from a meeting (the guy totally flaked on me, didn't even show up - good times), I mixed, poured, and did my best to vibrate / settle 500 pounds of concrete. I poured the part on the far end of the picture first, then moved on to the near part. I'd say that the split is roughly 275 pounds far, 200 pounds near.
This is the sink, and you can see thatI made a single seam this time, down the side of the sink. This was intentional. Rather than trying to match three seams (which wasn't working terribly well the first time), I only have to match 11 or so inches of seam. I have some hand diamond pads that will work well for this.
So here we have the pieces installed. There's a bit of shimming that may need to take place, but for the most part that's what the final product will look like. We're going to work on the tile for the back splash later in the week.
Here's the rest of it.
So here it is with the backsplash in.
Here's the other side.
And here's the counter top to the left of the stove. I pulled the piece of molding, so hopefully we can find a match and finish the grouting soon.