When it comes to casting concrete for a worktop using Cast-In-Place Mix, there are specific steps to follow to ensure a successful outcome. Here is a guide on how to properly cast concrete for a worktop:
How should you mix the Cast-In-Place Mix?
This firstly depends on what mixer you are using. For smaller projects you can get away with a paddle mixer such as the one in the image below.
Using this type of mixer you can mix 1 bag at a time. Any more and you'll be at risk of burning the paddle mixer out which is not ideal mid-project.
If you're doing a one-off project then you can use an ordinary cement mixer such as the one in the image below.
This type of mixer costs approx £200 but they can also be easily hired from a local hire depot. With this type of mixer you can easily mix two bags are once, however unlike normal concrete because our mixes are superplasticized and become very liquid, any more than two bags will result in the mix spilling out of the mixer as it turns.
If you're looking to make a living out of concrete then the Rolls Royce mixer would be a forced action mixer like the one below.
Image courtesy of Resco
This type of mixer can handle up to 4 bags at once and will make very light work of mixing.
Just remember, regardless of whatever type of mixer you plan to use, clean it thoroughly once you are finished with it. Concrete goes very hard!
If you are using a paddle mixer, then we could recommend that you have 2 tubs at least so you can have two mixes on the go at any one time.
When once mix is blended, it will require resting for 10 minutes to Degas (let air out), so you have time to get on with the next one.
For larger projects thus larger mixer, more tubs will be required. Mix a two bag batch up, leave to rest for 10, and mix another 2 up. For the larger mixer further tubs can be used again. You get the idea.
How do you pour the mix into the mould?
After the mix has rested, give it a quick whisk and pour it into the mould. If you have a paddle mixer then use that. If you are using a larger mixer then a mains powered drill with a mixer paddle will do the trick. As you pour, work your way along the moulds, filling them up to 5mm lower than the top of the edgeforms.
When should you move on to the fibre-free mixes for the facecoat?
Once you have filled up the moulds to approximately 5mm below the top of your moulds, wash your mixer down. Get rid of any residue and fibres from your mixer. this is quite important.
Check the firmness of the concrete where you started. It should have consolidated enough to move on to the fibre-free mixes for the facecoat. A good tip is to pat your hand on the concrete. If it feels firm, but a bit of wet mix comes off one your gloves (yes definitely wear gloves) you can proceed to the next step.
Mix the face-coat up in the same way but without the fibres. This will flow more easily again than the fibre-loaded backcoat. Allow to de-gas for 10 minutes and then its ready to pour.
By following these steps and tips, you can successfully cast concrete for a worktop using Cast-In-Place Mix. Remember to take your time and ensure each step is done correctly for the best results.