*** This post was originally written over 1 year ago and I have finally gotten around to posting it. Please see edits below. ***
When I was researching how to make concrete counter tops, it was nearly impossible to find good information on what "recipe" to use. So, as I gathered the little bits I could find, I combined it with the information available on each product I used and came up with a recipe. However, please remember, I am NO EXPERT! I have made exactly 1 counter top (though it was a really big one - 100 square feet!.). I have yet to take the molds off the counters, grind, polish and seal the counters but, I still think there is merit in sharing what we did and then you can take it or leave it! :)
First, let me share which products we used to make our counters. Quikrete makes a Counter Top Mix product that would be so easy to use. You simply add water and you have the perfect mix for counter tops. I did look into this option but found it to be really pricey. Here in the Winnipeg, MB area, it costs $48.99 for each 80lb bag AND it is only available at a Home Hardware store a 1/2 hour drive away to a little town. Home Depot does not carry it and will not order it in. Neither will Rona. I also checked my local hardware stores and they couldn't get it either. I checked numerous stores and only the small Home Hardware in Morris could order it for me. But, at almost $50 per bag, that option was too expensive since we were going to need 35 - 80lb bags. Instead, we made our own mix.
After reading about its merits, we decided to use Quikrete 5000. It is a high-strength cement mix readily available at building supply stores. We were able to get it from our supplier for $10 for each 60lb bag. From my reading, it was suggested to add 5lbs of extra portland cement to each bag of Quikrete 5000 to increase the cement content making the final product even harder, perfect for polishing. We certainly used this advice and ordered 4 bags of grey portland cement.
In order to make a counter top-worthy mix, we also needed to add fibers for strength and a superplasticizer to decrease the amount of water used in the mix, strengthening the final product. The fibers help reduce or eliminate cracks (as does the use of wire mesh and rebar) and the superplasticizer allows us to reduce the amount of water used in the mix, allowing for a stronger and harder final product. We were able to find our fibers and superplasticizer at the local ready-mix company. They were quite willing to sell us what we needed. We used Adva 140 for the superplasticizer (13L for $100) and Fibermesh 300 for our fibers (900g bag for $12). We followed the guidelines found on the products themselves when figuring out how much to use but altered as we needed.
Finally, I wanted the perimeter counters of our kitchen to be a dark charcoal color so we used Quikrete Liquid Cement color in Charcoal. This is a super thick syrup-like colorant that you can add to your cement to color it up. You need to shake it really, really, really well in order for it to mix nicely. We were able to find the quantity we needed at the Home Depot located on the farthest end of the city, naturally (14 bottles at $11.52 per bottle)! I had wanted to use 1 1/2 bottles per batch but I was short 1 bottle so we cut it back a little to make due with what we had. It still produced a lovely charcoal color.
We also added metal lathe to all areas of the counters. When pouring the concrete into the moulds, we poured a layer, added the lathe and then poured more concrete on top to ensure the lathe stayed in the middle of the concrete. On the overhangs on both the island and peninsula and around both sink edges, we also added rebar for extra strength.
Now that you know what we used, let me share the recipe. The recipe is for one batch, which we made in a concrete mixer - we made many batches until we had all the concrete we needed.
For the charcoal perimeter counters:
3 - 60lb bags Quikrete 5000
15lbs grey portland cement
750mL Adva 140
1 bottle + 125mL Quikrete Charcoal Colorant
30g fibers (I believe we cut this back a little because it was getting a little too fiber-y)
6L water (this changed a little bit, depending on the humidity of the cement but it was pretty close to this each time)
For the lighter colored island counter where we seeded glass on top after:
3 - 60lb bags Quikrete 5000
15lbs white portland cement
750mL Adva 140
15g fibers (we cut down on the fibers due to the glass we were adding)
6L water (once again, this changed a little bit, depending on the humidity of the cement but it was pretty close)
We wanted the island counter to be a very light grey so we lightened it up by using the white portland cement instead of the grey portland for the dark perimeter counters.
When we mixed our batches, we made sure to measure each product accurately using scales and measuring cups. It is important that each batch is exactly the same as the one before it so that the entire counter looks consistent. When mixing according to our recipe, you will produce a thick, sticky concrete mix that trowels really nicely. I will be sure to update when we have polished our counters to show you the final outcome.
As for the cost breakdown, I don't have all the numbers yet but this is where it stands now:
Quikrete 5000 - 44 bags @ $10 = $440
Grey Portland cement - 4 bags @ ??
White Portland cement - 1 bag @ ??
13L Adva 140 (we only used about 11L) - $100
Fibermesh 300 - 1 bag = $12
Quikrete Charcoal Liquid Cement Color - 14 bottles @ $11.52 = $161.28
1 YEAR LATER:
I sincerely apologize for not posting this a long time ago. Time has run away from me and I have had no time to blog at all. However, I know the help this can be and so I am wanting to share it with you.
When we made the counters, I was unsure how I was going to finish them. I knew that I wanted a shiny surface that looked wet at all times. I knew that I wanted the perimeter counters to be dark grey/black in color. I wasn't sure how to get that look so we did some experimenting. I used the diamond polishing pads to polish the perimeter counters and though it made it really smooth, it wasn't shiny. Though we had added the charcoal colorant to the concrete in the perimeter counters, I still wasn't impressed with the depth of the color. It also looked blotchy, which I didn't like. We remedied that by spraying the raw concrete with a black colorant meant for concrete floors. This is the product we used in the Obsidian color. We already had it on hand because we stained other concrete floors with it. I LOVED how it evened out the color of the concrete and made the counters much darker. I finally had the color I wanted so it was time to seal it. Knowing this, we would never have added the colorant to the concrete mix itself but that is one area where we lived and learned. As for the island, the glass did not allow me to polish it with diamond pads as it would have taken forever. Initially we used a concrete grinding disk to grind the glass down smooth and then used the diamond polishing pads to get it progressively smoother. Once we had the counters smooth, it was time to seal them. After doing some experimenting with products on our test piece, we finally choose to use an epoxy-type sealant. It was purchased at Menard's and was fantastic! It is a two-part system that you mix just before you apply it. We had to ensure a dust-free environment so that was a challenge in a construction environment but we were able to do it. The epoxy was easy to use and gave me that glossy wet look that I wanted. The colors of the black counters and the glass really popped! There are a couple of places where I was unable to get the air bubbles out of the epoxy but I am okay with that. After using the counters for 1 year, I am still in love with them. Oh, sure, there are hairline scratches on the epoxy on the counters because they are used a lot but I can always recoat them with more epoxy anytime I want. I have seen absolutely no cracks in any area of the concrete counters themselves, including all the overhangs. And we use our counters a lot, even sitting on them!
To see final pictures of our kitchen and check out what the counters look like, see this blog post of our Kitchen Tour.
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