The CONCRETO Code Book represents foundational research conducted within the broader framework of the CONCRETO Academy Project, officially launched in 2024. The CONCRETO Academy was established to address the increasing demand for specialised skills and craftsmanship in the conservation of concrete historic architecture. Leading this initiative, the Pier Luigi Nervi Foundation has played a pivotal role in safeguarding modern heritage, driven by its commitment to preserving the profound legacy of the Italian engineer-architect and builder Pier Luigi Nervi. Designed as a research hub, the CONCRETO Academy develops training programmes rooted in the principle of Learning by Doing, blending theoretical knowledge with technical expertise and hands-on practice. Participants of the Academy are not students, but fellows engaged in an apprenticeship model that fosters active skill-building and knowledge exchange. The Code Book serves as the foundation upon which all teaching and learning activities within the Academy are structured. While primarily focused on the European context, its reach extends globally, leveraging insights from the extensive CONCRETO Network of partners and experts. Through rigorous literature review, open questionnaires, and strategic interviews, the Code Book defines the current state of concrete conservation, identifying key challenges and opportunities within the field. This publication is intended for all professionals engaged in the conservation of historic concrete architecture.