Concrete by nature is heavy so we recommend that for any larger decorative concrete panel items such as tabletops or countertops that a maximum thickness of 20mm is designed. To create the appearance of thickness we recommend that a “lip” be formed around the perimeter of the item.
Following is the basic method by which this can be achieved.
1 The Basic Formwork
The basic formwork is created using a base material, strips of formwork and reinforcement blocks. Melamine is recommended as the material. Hot glue is recommended as the adhesive.
2 The First Cast
After mixing your first batch of concrete pour into the mould. This should ideally self-level after a period of a few minutes. Each mix should be poured on top of already poured concrete to ensure a homogenous layer.
Once the base has been fully poured to a thickness of approx 20mm, the mix should be pulled up the outer formwork or “lips” to create an all important coating.
We recommend using the Concrete Lab Worktop Premix for the concrete as it has all the correct ingredients and has a fool-proof methodology for imperfection free concrete.
3 Final Formwork & Second Cast
After 2-4 hours the inner formwork can be constructed using melamine strips and hot glue. A caulk bund should be incorporated as located in the images below to prevent leakage of the secondary mix.
Once the inner formwork is in place and secure the secondary mix can be carefully cast.
Once the cast is complete the concrete should be covered with plastic sheeting to prevent moisture loss. This is imperative to ensure high and early strength gains.
It is also recommended that the concrete be cured at 21degC and no less than 18degC. Heated blankets should be considered if the workshop temperature cannot achieve this.
Assuming that step 4 has been achieved, demould can take place after 24 hours. Carefully remove the formwork to ensure that you do not damage the concrete before full strength has been achieved.