Dani,
Ruts happen on asphalt, and the 33/F/B/X/U rating for Corfu says it is asphalt. Ruts don’t happen on concrete, but the edges/corners of much overloaded concrete slabs can spall and break and that can give you fist size or even wine-bottle size chunks of concrete lying on the surface. What is an FOD possibility with asphalt is an FOD certainty with concrete.
I don’t know WSSS but I suspect it presents a slightly different problem which is outside the earlier discussion. Starting point is that there are a first class bunch of airport engineers there, so whatever happening would be under close surveillance.
My Google Earth shows the taxiways to be asphalt. If there is rutting greater than 1cm on an asphalt taxiway, then there could be an issue or maybe it is just that the taxiways are coming to the end of their life. I can see the pattern of pavement repairs on the airport, and they certainly could be related to slow speed and viscous flow of the bitumen in the asphalt. As well as a weight problem, that is a low speed problem and a high temperature problem (and the two are interchangeable in describing the behaviour of asphalt: low speed is equivalent to high temperature. So the combination of low speed + high temperature is a double whammy. My own belief is that hot humid places are even slightly worse again, and as I type, I’ve just worked out why – the temperature stays high at night as well as during the day. Does that make WSSS taxiways a 2½ whammy?).
The WSSS problem could also be due to the extra damaging effect of the 777-300ER aircraft. These aircraft are much harsher on the pavement than the older 777-200 and 747-400 due to the significantly higher weight per tyre. I’ve seen some asphalt early rutting problems in the Middle East due to these aircraft, and the Middle East has temperatures which are hot, so problems would be expected to occur there first. I suspect those aircraft are quite common at WSSS, and so I wonder if WSSS is also being affected by this.
This is all part of the equation that is worked out when the PCN is determined by the airport, and the WSSS engineers would have predicted the end of the asphalt life years before it was actually reached.