By now there exist several methods to predict durability of reinforced concrete structures. In most cases one dominant deteriorating process such as carbonation or chloride penetration is taken into consideration. Experimental results as well as observation in practice show that this is not a realistic and certainly not a conservative approach. To develop more realistic test methods, RILEMTC 246-TDC has worked on the determination of durability of concrete under combined environmental actions and mechanical load since September 2011. This report introduces a test method which can realistically determine the chloride ion diffusion coefficient of concrete under compressive and tensile stress. Comparative test results among 5 international labs showed that the combination of mechanical and environmental loads may turn out to be much more severe than each single environmental load alone in the mechanically unloaded case. Modelling and probabilistic analysis also showed that the obvious synergetic effects can’t be neglected in service life prediction.