Concrete Counter-Top Begins

  Looking forward to seeing the temporary vanity top gone.
This is why!!!!!
Luckily for us, we have experience in the concrete world.  No, not like a mafia body disposal business, but more like actual bodies of functioning concrete.  Our bathroom vanity top will be our seventh concrete counter-top

  
We started out about five years ago in our kitchen and they have held up well!

One of the counter-tops in our kitchen

    

  The first step is to build the mold. 
  Everything we do is upside down.

We cut the base to the exact dimension of our finished counter-top.

The sides of the mold are cut to the depth we want our counters to be, plus the measurement of the melamine (3/4 inches)  We chose 2 1/2 inches for the tops so our board was cut to 3 1/4 inch strips. All screwing is done on the outside of the mold.  You don't want screw heads inside your mold as it makes an impression in the concrete.

The sink placement is determined and layout lines are drawn on the base of the mold.  We routed the corners for the sink cutout to ensure a proper radius.  See bottom right photo. 

The sink cutout is assembled according to the template provided with the under-mount sink. 

We decided to add a draining soap dish.  We cut some melamine in the shape we desired.  The edges are routed to create a curved transition.  Where the board meets the sink cutout, we used washers to shim it up so that the soap dish will drain to the sink.

Frame completed.  Sink faucet cutout is installed too,  (awkward looking oval thingy in bottom right picture).   All joints are silicon-ed.  We use a dark silicone so we can see where it is.  It is applied very thinly and smoothed with Popsicle sticks so we don't end up with a really curved edge.     Remember all things put in mold will determine the finished product.

 Another part of the mold is ROCKS.  We use local aggregate but we always head to the lapidary for a few fancies.  I have ordered ammonites on E-Bay and used them in a few of the pours.  This time around we used an assortment.   Heavy gauge wire Vs (bent wire in the shape of a v) are fabricated and adhered to the backs of the rocks with epoxy.  This is just a bit of insurance that the rocks with smooth backs will have more adhesion to the concrete.

We put rebar in our tops to ensure strength.  This is why we pour 2 1/2 inches.  You can make your molds shallower and just use concrete mesh, but you give up strength in doing so.  Rebar is bent to the shape of the mold but smaller.  We use two pieces, one for the inside edge and one more for the outside edge.  Corners are welded, but you can tie them with wire if you don't have access to a welder.  We attach concrete mesh to the rebar using  thin wire which holds it all together.  This structure needs to sit about half way in the pour.  To do this, we screw screws to the outside of the mold.  We wrap wire around the rebar and then hang the wire over the side and then wrap the other end of the wire around the screw.  We usually attach at least 2 screws per side pending on how large the mold is.  With this size, we used 10 screw on the outside and 6 screws on the inside where the sink cutout is.  When concrete is poured, and vibrated and somewhat leveled out, we cut the wire just below the concrete surface so that the screeding can be done.

  Screws attached on the outside of the mold walls are wrapped with wire and secured to rebar to ensure rebar sits halfway  in mold.  Should float around the center for proper strength, and no shadows in your finished top.  After concrete is poured and somewhat leveled, wire is snipped off just below the surface of the concrete.

An important part of the job is to figure out how much Portland cement, sand, gravel, water, and other ingredients to use.   We build our counter-tops 2 1/2 inches thick.  Which means this one would be 35 x 26 x 2.5.  We decided to mix up 1 cubic foot of mix.  As our mixer is a small one, we

 pre-measure our ingredients into two batches which keeps the color the same.  We created a custom color of  sandstone and black.  We felt this would add enough grey to our brown and darken it to our liking.
Our mix for one cubic foot is:

24 lbs High Early Portland Cement
37 lbs pea gravel
72 lbs sand
1/2 ounce polypropylene fiber
4 cups of colorant
3 ounces water reducer
water to make a very thick mix

Water reducer makes for a sloppier mix, so be very frugal with the H2O.  Too sloppy of a mix makes for your aggregate to sink to the bottom of the mold which is visible on the sides of your counter.  Also this weakens your concrete.  You want a fairly thick pour that hold its shape. 

Above are a few of the ingredients used for our mix.  Not shown, is Portland cement (high early), sand, polypropylene fibers, and H2O.  Show from left to right: 1. aggregate,  2. powder colorant,  3. pre-measured Portland cement, color and sand.  4. and last picture is water reducer.

Now  the pour.  Concrete is added to the mold, and with latex gloves to protect our hands, we force the concrete around all the obstacles in the mold, ensuring it is forced into all the corners.

With a vibrator, (the concrete kind ),  the mold is vibrated to remove air bubbles from the mix.  We just vibrate the outside  and the bottom of the mold.  This seems to remove most of the unwanted air bubbles     The counter is screeded off.  This is the bottom of the counter-top so perfect smoothness is not necessary.  You do however want it to fairly smooth as the sink will be mounted directly to this surface.

 

  We wait for approximately an hour, go back out for the final float.  Since the start of our concrete counter fiasco's, we have put leaves in the bottom of our counters.  Mostly, they are not visible, but we know they are there;  our signatures.  I found an Oak and Hawthorne leaf for the job.  In doing so, I am guessing scientists will use  DNA from the imprints and recreate these extinct trees in the year 2824 and from there they will be able to grow "Ents", and send them to other planets to create new civilizations! 

This is the bottom of the counter-top.

Counter-top is covered with plastic and kept moist for the next few days to ensure a slow cure.  

Stay tuned for the final stages.......Our counter-top has to stay in the mold for three week!
All done now.  To see the finished beauty, CLICK HERE!!!!!!!
Cheers!