Well before the actual work begins, set out the criteria for evaluating how concrete surfaces should look. What concrete surface pattern/grid does the project owner want to achieve? What requirements apply to the concrete surface texture? What shade of colour should the finished concrete have? These are some of the criteria that will subsequently play a major role by choosing the right formwork and the right concrete mixture.
The formwork system is a major factor for the concrete finish. The arrangement of the form ties and the footprint made by the frames at the inter-panel joints will subsequently appear on the surface, patterning the visible part of the concrete.
The guide below will support you in the selection of the right Doka formwork for fair-faced concrete:
The right concrete recipe plays a significant part in concrete surface quality. The recipe affects the porosity and the coloring of the concrete, as well as the overall outcome of the concrete surface such as the appearance of rock pockets, creeping water effects and lime efflorescence.
There are available solutions that can support you in the definition of the suitable concrete mix for ensuring a similar colour tone throughout the concrete surface. Doka customers rely on Concremote for optimal results of the concrete structure.
With regard to the appearance of the concrete and the absorbency of the formwork sheets there are big differences between used formwork and new formwork. This can have consequences, including differences in the colouring of the finished concrete surface. So avoid mixing new and used formwork.
Adapt the concrete recipe to weather conditions and note the following: At ambient temperatures <10 °C it becomes very difficult to produce fair-faced concrete to standards compatible with high requirements. This has an effect on stripping time and fresh-concrete pressure. For example, when the stripping time is prolonged during the cold weather conditions the concrete surface might appear darker.
Keep in mind that in hot weather conditions the formwork panels could warm up significantly. This could lead to quick drying of the concrete during pouring. After stripping the resulting flaws are visible on the concrete surface. Also, it is possible that the concrete starts stiffening sooner than normally when the temperatures are too high. Possible solutions are pouring of the concrete in the early hours of the day, using shades, or cooling the concrete with ice.
Start curing immediately after stripping and protect your concrete surface with foil that does not come in contact with the concrete. Avoid allowing any air flow between the concrete surface and the covering foil.