nfrastructures and buildings are exposed to microorganisms in a variety of contexts. RILEM 253-MCI Technical Committee (2013-2018) aims to implement concerted approaches and comparison of research outcomes to move toward a better understanding of the phenomena and furthermore, to standardization (of test methods for example, there is a real shortfall in the domain) and/or certification. The Delft conference, organized at TU Delft on 23 June 2016, was the midterm event of this TC. The conference consisted in (i) review presentations given by the TC members on the topics listed below, and (ii) a poster session by participants in the conference. These proceedings gather the review papers presented posters’ abstracts. Topic 1: Deterioration of cement-based materials by microorganisms in different contexts Topic 2: Proliferation of microorganisms (algae, fungi) on building materials in outdoor conditions Topic 3: Proliferation of microorganisms (algae, fungi) on building materials in indoor conditions Topic 4: Engineered bacteria-based protective systems for cementitious materials @en