TY - CONF A1 - von Werder, Julia T1 - Greening Concrete with biofilms: Codesigning with nature N2 - uilding envelopes act as artificial lithic surfaces and natural substrates for subaerial biofilms, whose establishment depends on surface bioreceptivity. This study investigates how concrete cladding can be engineered to support microalgae‑dominated biofilms. A multi‑stage experimental framework—ranging from petri‑dish cultivation and adhesion testing to laboratory weathering simulations and outdoor exposure—was applied. A reproducible dual alga–fungus model biofilm enabled controlled assessment, with algal vitality quantified using PAM fluorometry. Results identify pH and carbonation as primary determinants of successful colonization, while nutrient addition has only minor influence. Adhesion tests show that moderate stress can enhance resilience to hydrodynamic forces. Rain‑simulation experiments highlight the importance of surface texture and near‑surface porosity for water retention, microbial attachment, and sustained growth. A synergistic interaction between algae and fungi under stress conditions may explain the poor outdoor performance of biofilms cultivated under ideal laboratory conditions. Overall, optimizing photosynthetic efficiency, organismal growth, and adhesion strength is essential for developing durable algal biofilm‑based façade systems. T2 - 4th International Conference of Sustainable Building Materials CY - Eindhoven, The Netherlands DA - 10.08.2025 KW - Concrete KW - Bioreceptivity KW - Laboratory test KW - Biofilm KW - Fluorometry PY - 2025 AN - OPUS4-65447 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -