Despite intensive research on material properties of non-metallic technical textiles for internal reinforcement in concrete, the long-term durability is not yet fully understood. In this work, results of preloaded long-term durability tensile tests on carbon-reinforced concrete specimens under environmental factors of stress, temperature, moisture and alkalinity are presented. Based on investigations of non-metallic glass fiber reinforcements with polymer matrices, where strength losses occur over time, it was planned to derive a time to failure curve and to determine a reduction factor for the tensile strength of the carbon textile reinforcement. However, no loss of strength was discovered in residual capacity tests due to the high material resistance and therefore no reduction factor due to the environmental factors could be derived. After more than 5000 h of testing, the residual capacity tests showed an increase in the ultimate failure stress in comparison with the short-term tests. In addition to the long term-durability tests, the influence of the preloading was investigated. The preload was applied to the long-term tests and led to a straighter alignment and loading of the filaments and thus to an increase in the ultimate capacity.