Strengthening of Existing Bridges in Germany Using Carbon-Based Materials: State of Practice and Regulatory Framework for Carbon-Reinforced Concrete and Externally Bonded CFRP Laminates

Germany’s bridge infrastructure is increasingly affected by aging, rising traffic demand, and the need to reduce the environmental burden of replacement construction. In this context, strengthening existing bridges has become an important strategy for extending service life while limiting material consumption, CO2 emissions, and traffic disruption. The present paper reviews two approaches to carbon-based strengthening in bridge rehabilitation in Germany: carbon-reinforced concrete and externally bonded carbon-fiber-reinforced polymer (CFRP) laminates. The paper presents a state-of-practice and research review, technical guidance, approval documents, and exemplary practical applications and discusses both systems in terms of material behavior, strengthening principles, durability, fatigue-related performance, and current regulatory status. This work follows a semi-systematic methodology, drawing on peer-reviewed literature (ResearchGate, Google Scholar) and German technical guidelines, approval documents, and documented Germany-based bridge case studies published between 1999 and 2026. The review concludes that CFRP laminates are a rather mature and widely established technology, while carbon-reinforced concrete is a newer but increasingly validated solution with advantages for thin, lightweight, and durable strengthening measures. Both systems generally offer high potential for sustainable bridge strengthening but still require further development in terms of standardization, long-term assessments, and broader application.