Towards a new vision for war heritage: preventive conservation and adaptive reuse of massive structures

The conservation of war-built heritage (WBH), especially war massive constructions often referred to as “Dark Heritage”, is widely debated due to the dramatic events of World Wars and the related memories they continue to evoke. Initially perceived merely as symbols of occupation and conflict, these defensive structures were rarely preserved or adapted to new uses. Over time, as their demolition proved impractical and costly, a growing interest in their reuse has emerged, fostering a new understanding of war heritage as a social, historical, and economic resource. Public perception has gradually shifted toward acknowledging these sites as valuable witnesses of twentieth-century history, worthy of preservation as spaces for education, reflection and remembrance. Long abandoned and often in deteriorated state, these massive, heavy-weight structures present complex conservation challenges, but also great potential due to their dimensions, construction features, and impact on the surrounding landscape—often acting as architectural landmarks. Their heavy-weight construction can support sustainable reuse, and in the field of cultural heritage, such buildings could be integrated into preventive conservation strategies. However, any potential transformation requires careful consideration to ensure the preservation of their historical value. This doctoral research addresses an emerging topic in modern heritage conservation, focusing on the preventive conservation and adaptive reuse of massive WBH structures to define integrated and sustainable approaches for their preservation and management. Three complementary domains are investigated: i) appearance, focusing on salt-related decay in historic reinforced concrete ; ii) use, investigating the potential of heavy-weight constructions as passive conservation solutions; iii) transformation, exploring how changes in appearance and use over time can affect public perception and ensure the long-term preservation of both materiality and memory. The methodology reflects this threefold approach and is applied to the pilot case study of Dora I, a World War II reinforced concrete bunker in Trondheim (Norway). The first domain integrates non-destructive testing (NDT), image-based methods, and climate data analysis to assess salt-related decay and moisture content behaviour in historic reinforced concrete. The second domain deals with a microclimate-driven method to quantify the passive buffering capacity of massive buildings, and with a climate-induced conservation risk assessment through dose–response functions. The third domain combines spatial, archival, and online feedback analyses to investigate how transformations in appearance and use influence public perception and conservation perspectives. The outcomes related to the three domains can be summarised as follows: i) climate-induced moisture content variations and salt-related processes are key drivers of visible decay in concrete, while handheld moisture meters can detect relative variations but require calibration on historic heterogeneous materials, ii) the microclimate-driven method proves effective as an evidence-based decision-making tool for supporting adaptive reuses of heavy-weight buildings, revealing Dora I building’s capacity to delay and attenuate outdoor climate fluctuations; iii) analyses on WBH’s appearance and reuse changes reveals that transformations strongly shape public attitudes, with balanced and responsible strategies, preserving both the tangible and intangible values of war heritage. Overall, the thesis proposes an integrated framework for the sustainable preservation of massive WBH, emphasizing the importance of interdisciplinarity between STEM (Science, Technology, Engineering, and Mathematics) and SSH (Social Sciences and Humanities) fields, to safeguard both the materiality and the memory of twentieth-century war heritage in an era of climate and cultural transformation.