## 8 Conclusions and Outlook  
The long-term durability is the combined investigation of creep and alkaline resistance. A test method, which was developed by [PERSON] and [PERSON] [17] and combines both exposures, was applied to small-scale specimens with a high-strength concrete and a single layer of an epoxy impregnated carbon reinforcement. To determine the long-term durability of the carbon reinforcement, short- and long-term, as well as preloading, tests were performed. Based on the short-term tests, the load levels for the long-term and preload tests were determined.  
The results of this work can be summarized as follows:  
* The long-term durability behavior of textile reinforcements is generally influenced by environmental factors, such as stress, temperature, moisture and alkalinity (pH-value). For this purpose, test rigs were developed which allow a combined exposure.
* Long-term durability tests with up to 11,000 h test time at temperatures of 40 and 60 \({}^{\circ}\)C were carried out at load levels of 70 to 97% of the reference load determined in short-term tests. With one exception, there was no failure due to the applied constant load levels.
* An increase of the ultimate load compared to the short-term tests could be identified in residual capacity tests. A load-oriented alignment of the filaments (training effect) is assumed, which leads to the higher load capacities of 10 to 17% compared to the short-term tests.
* Preloading tests at 60 \({}^{\circ}\)C confirmed this observation. After 24 h of preloading at 50% of the ultimate reference load, the residual capacity was 7% higher than the reference load.  
Based on the long-term durability tests presented in this paper, it is not yet possible to derive a time to failure curve or a loss of strength for the material combination presented in Section 4. This corresponds to the test results of carbon reinforcement described in literature, where no or only minor strength losses were found. Within the framework of the C\({}^{3}\)-V2.1 project, further investigations will be carried out to validate the long-term durability of this and other material combinations with non-metallic carbon reinforcement. The aim is to determine the loss of strength over 100 years for this reinforcement to be able to safely and economically design carbon concrete components. As an outlook, it currently appears possible that no reduction due to external influences is necessary for this type of reinforcement. Moreover, the influence of a preload shall be further investigated.  
Conceptualization, A.S. and S.B.; formal analysis, A.S. and J.B.; experimental investigation, A.S.; data curation, A.S.; writing--original draft preparation, A.S.; writing--review and editing, A.S., S.B. and J.B.; visualization, A.S. and S.B.; supervision, J.H.; project administration, J.H.; funding acquisition, A.S. and J.H.  
This research was funded by BMBF, grant number 03 ZZ0321C.  
The authors thank solidian GmbH for providing the carbon textile reinforcement.  
The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.