Just registered on the forum, so I can see responses easier.
I have done a lot of research into concrete worktops, and done lots of test samples (22 in total!).
The reason I have researched it so much is I wanted as white a worktop as possible, with some white aggregate showing. This, as I found out, is no simple task. But I have now nailed the mix design.
I am planning to pour the main worktops in 2 weeks time.
Some people as asking what products have been used, and where to get them. So I thought it would be helpful to post my shopping list.
The Frame:
- 8 x cheap sawhorses from screwfix (£20 a pair, cheapest I could find)
- Timber to build a casting platform on the sawhorses, which was designed to hold the melamine board flat. (Essential to stop it bending with the weight of the concrete)
- 18mm White High Gloss Melamine Faced Chipboard 2800mm x 610mm for the forms. I bought mine from
www.melaminefacedchipboardstore.co.uk but would not recommend them. After I order it I found my local timber merchant had them cheaper and a faster service. I also bought a smaller sheet to rip up with a table saw for the edges of the frame, and glued them down with my kids hot glue gun.
- Rust-Oleum ROLFFWCL400 Furniture Finishing Wax, Clear, 400 ml - From Amazon. This was for waxing the form before I applied the silicon. (See Jeff Girard's video on how to prepare frames)
- No Nonsense General Purpose Silicone Sealant Black 310ml - From Screwfix. This was for caulking the edges of the frame.
The Concrete Mix:
I went for a ratio of 1:1.77:1.77
Slightly odd proportions, I know. But I tried lots of other ratios first, which did not work so well.
The above is what is recommended by the Concrete Countertop Institute, and worked out by the far the best in my trials.
The critical bit is the cement to water ratio. This needs to be as low as possible. Ideally 0.35, but the best I managed was 0.45 (due to my pigment and large amount of fines making the mix dryer). Anything above this is too much water and will make weak concrete.
- Cement = 25KG bag of snowcrete (white) from Jewsons (£12.95)
- Sand A = Cristobalite White Silica Sand, 25kg Bag Grain size Fine 0.25mm-0.5mm. £21.84/KG delivered. Supplier is
www.trustleaf.co.uk/natural-white-silica-sand-3977-p.asp - Sand B = Anti Slip Crushed Glass 0.3-0.8mm, 25KG Bag is £33 (NOT delivered, collection from Bakewell). Supplier is
resinbondedaggregates.com/product/anti-slip-crushed-glass - Fine Aggregate = Daltex Arctic White 1-3mm. 25kg Bag is £28.58 (NOT delivered, collection from Bakewell). Supplier link is
resinbondedaggregates.com/product/daltex-arctic-white-1-3mm - Course Aggregate = Daltex Arctic White 2-5mm. 25kg Bag is £28.58 (NOT delivered, collection from Bakewell).
resinbondedaggregates.com/product/daltex-arctic-white-2-5mmAdditives:
- Super Plasticiser = BASF Melflux 2651 - 1 x 1LB Bag from Globmarble on their Ebay shop or direct from website
globmarble.com/. Watchout for the deliver and customs charge - They are much more than the product. This product was a last resort for me. I tried many UK based Super Plasticisers and nothing came close to the power of this product. I needed it because of my large number of fine ingredients, and the pigment I used. Most people won't need this. Cost was £76.65 for the product, delivery from New York, and customs charge.
- Pozzolan. This makes the concrete much stronger. Cheap UK products are available from Cemcraft, but are not white. I needed white. So I managed to source a 25kg bag of BASF Metamax from a friend. Not normally available in the UK to consumers. And again, unless you are wanting a pure white worktop, this specific product won't be needed. Cheaper alternative is:
www.cemcraft.com/White_Microsilica__10Kg--product--277.html - White Pigment = Whilst all my components were white, I was still getting a grey end result. So I used some white pigment from Cemcraft. Expensive, but it worked. Cost £22.50 for 1KG from here:
www.cemcraft.com/Titanium_White_Rutile_Form_Pigment__1Kg--product--297.htmlPolishing
- Wet Polisher = ZFE 230V Wet Polisher / Grinder & Granite Diamond Polishing Pads. £130 from amazon here:
www.amazon.co.uk/gp/product/B00KT2BQLQThe polisher worked an absolute treat, bringing my samples up to a very very high shine. Like polished marble.
Any questions, please feel free to ask.
Thanks,
Paul.