Runways and taxiways are designed for different purposes than aprons and parking areas. In particular they are not designed for accommodating static loads, therefore aircraft storage on those areas increases the risk of permanent deformations. It is estimated that 90% of aprons and aircraft parking areas world wide are made of concrete slabs (PCC) to minimize the risk of permanent deformation when they are subjected to static loads.
Base course strain 3D heatmap
Longitudinal strain profile at the bottom of base course
Bituminous materials have a viscoelastic behaviour and their modulus of elasticity depends of the temperature and the load frequency/speed (bituminous material rheological properties). Consequently, the slower the speed, the lower the (complex) modulus of elasticity and the higher the shear strain at the bottom of the bituminous layer. For this reason, parking and aprons (where aircraft operate at low to very low speed) are usually made of concrete slabs. The strength of taxiways (moderate speed section) is greater than runways (except in some cases on runway thresholds), but lower than parking/aprons which are purposely designed for accommodating static aircraft loads.
It should then be understood that taxiways subjected to static aircraft loads are more sensitive to permanent deformation than those subjected to moderate or high speed loadings.
A380 parked on taxiway