Microstructural consolidation of mortars' surfaces by the use of di-ammonium phosphate (DAP) as an innovative treatment in cultural heritage buildings.

The thesis deals with the question of microstructural consolidation of lime-mortar surfaces by the novel innovative phosphate-based treatment – di-ammonium [hydrogen] phosphate (DAP). Through the analysis of multiple case studies and by retracing the development of the use of different artificial consoliding products from 19th century till today with the indication of their results, reasons of searching further improvement and transformation of general conservation foundations for that type of intervention it gives the answer to the question of urge to introducing a new artificial consolidant in the historic materials’ conservation field. Therefore the foundation of the thesis is to indicate in what ways, to what extent, and under what conditions multiple artificial consolidants used in the historic buildings influence the process and results of consolidation on different lime-based surfaces. The attempt to seek for the reasons of what are the main factors determining the treatment of specified stone, mortar, plaster or wall-painting surface by micro-consolidation is to be subjected. The assessment of different conditions, such as environmental impact, severe damage, vast cleaning, etc. will be evaluated and confronted with a different diagnostics campaigns and monitoring observations. The core part of this thesis is devoted to the investigation of the possible use of a novel inorganic consolidant – DAP – on the lime-based mortar surfaces. This aim is supported by an experimental laboratory testing and on site trials allowing to assess its effectiveness and optimize further activities concerning its use. The examination provides the information regarding crucial characteristics of the treatment, particularly in terms of mechanical properties’ change, consolidant’s penetration depth, superficial color modification, water absorption rate alteration and its behavior towards weathering action. Additional on site application performed on the historic artwork provides an essential complement of the actual usability of the proposed treatment. DAP consolidation effect, tested firstly on the original samples compared to the control group is – in the subsequent parts of this thesis – as well evaluated on the highly degraded surfaces, obtained by accelerated ageing (freeze/thaw and salt crystallization cycles). The treatment method is subdivided into two parallel application processes, from which the first one concerns only DAP treatment, while the other adds as well limewater application as a second step. The results of those two adapted treatment methods indicate significant differences particularly in case of field studies. The outcomes of the research provide the first deepen insight on the DAP treatment of mortar surfaces and clearly indicate, that the proposed method of consolidation pose multiple advantages. Particular effectiveness of the treatment was observed in case of mechanical properties’ improvement (microstructure strengthening and enhancement of surface cohesion), mainly in case of the samples suffering from previous weathering degradation. This dependency was observed both in laboratory conditions and on site. Minor color change deriving from the treatment was observed in each of the proposed modality, which issue is considered as the quality that ought to be overcome in further studies.