Now there are three garantees in life death taxes and concrete cracking. Plenty can be done to minimise cracking and to try to prevent it but at the end of the day there is more than likely a crack there (whether is is visible or not). So what does cracked concrete mean for polished concrete?
Honestly not too much, cracks can be repaired. Depending on the size of the crack will dictact the way the crack is fixed. Small micro-cracks can simple be grouted during the grouting step and this will cause them to simply disappear into the floor and you can only find them when really lookig for them. Other times slightly bigger ones will need a polishing product using such as Ardit A45 or Rapidset Tru. In the more extreme cases you will need to epoxy fill these cracks. The benefit of the epoxy system is it is still flexible and will allow more movement within the concrete. The grouting and the A45 will fill the crack and allow the floor to be polished however if there is still significant movement within the concrete slab then microcracks will open up along the patch and the patch may fail.
In this case in Cairns this week, the concrete wasnt initally poured to be polished concrete. It was only 25MPA and made to be tiles. This is a suspended concrete slab supported by pillars underneath on the side of a hill. In this case there was significant cracking due to the movement. The cracks ranged betwnee 5-10mm wide. It was decided the best way to correct these cracks and allow for a polished concrete finish was to epoxy fill. We use C2 Crack fix for this type of job. This product is so easy to use and perfect for this job (see C2 crack fill). We were able to successfully fill the cracks and then proceeded to grout and polish the floor. See below to see how the project turned out.