NIL EXPOSURE/LIGHT RANDOM - for new slabs (We grind off 1 – 2mm)
LIGHT RANDOM EXPOSURE is where the least possible exposure of aggregate and sand is sought. This finish is totally reliant upon the quality of the slab as any flaws and screed marks will be accentuated and very visible. The condition of a slab must be absolutely perfect to achieve a professional looking SALT and PEPPER or LIGHT RANDOM finish!
If you, your architect or designer really desire this look, it is really important to understand the complexities of achieving your expectations. A nil exposure floor, especially if a matt finish is specified, can look not much different to what one would expect for a garage floor if the concrete slab has not been poured and finished by a professional, knowledgeable concretor who understands what is required.
The slab must be flat and highly burnished, achieved by as many passes as needed (multiple) with the helicopter (powered trowel) by the concreter. Screed marks and footprints must be removed. The concreter needs to burnish, as close to the edges as possible, otherwise unevenness in the finish will result introducing random aggregate exposure.
Evenly vibrating the slab during the pour assists the aggregate and sand to sink, leaving more cream on the surface and reducing the chances of stone being visible when the buff, grind and seal, or polishing procedure commences.
EVEN WITH THESE STEPS, THERE IS NO GUARANTEE THAT SOME DEGREE OF PEBBLE OR SAND WILL NOT BE EXPOSED IN SOME AREAS. (The slab should definitely not be poured on a wet or very cold day, as this will not allow your concreter to finish the slab to a high enough standard).
IT ALL STARTS WITH THE CONCRETER AND THE SLAB! We can't STRESS enough how important it is to have a GOOD CONCRETER!
As uneven burnishing results in an uneven floor, we at CCC will inspect the slab before we proceed and report the outcome to you or your authorised representative e.g. builder. As stated above we cannot be responsible for the standard of the slab and as such can not guarantee that some screed marks, some areas of more exposure than desired, or footprints may be visible once the surface has been grinded off. Similarly, if the concreter leaves dips in the floor, these will also be highly visible in this LIGHT RANDOM EXPOSURE finished product.
A close to nil exposure can also be achieved through a grind and seal finish.
