Activities of EMASST for the restoration of the Crypt of Sant’Agnese in Agone in Rome.
EMASST is involved in the preliminary activity of scientifical research, aimed to evaluate the state of preservation of the Crypt of Sant’Agnese in Agone in Rome.
The Crypt of Sant’Agnese in Agone is placed at Piazza Navona, one of the main urban spaces in the historic centre of the city and the crypt is the site where the Early Christian Saint Agnes was martyred in the ancient Stadium of Domitian. In fact the Crypt was built on the rests of Stadium of Domitian.
The crypt is currently closed to the tourists since, after its last renovation in the 1893, it was undergone to natural catastrophic events (floods of Tiber river, intense rains, etc…) that ruined the ancient frescoes present on the walls and ceiling of the Crypt.
There were big floods of Tiber river after the last renovation. In particular there were 3 floods higher than 16 meters on the sea level that certainly flooded and hurt the frescoes of the Crypt (1900, 1915 and 1937). In fact the water can enter in the Crypt from the floor and from the opened windows that are placed at the level of floor of Piazza Navona.
In addition from geological and hydrogeological analysis was demonstrated that Piazza Navona (and the Crypt) is placed in the alluvial plain of the Tiber River (Pleistocene Medium -
The analysis showed that the Crypt is placed at 12 meters on the sea level, the ground floor of Piazza Navona is at 15 meters on the sea level. The aquifer was measured in Piazza Navona in 3 points of measurements and it is placed between 8 and 10 meters on the sea level.
In addition under Piazza Navona, an ancient network of channels for the outflow of the water was identified at 13 meters on the sea level.
All of these information confirm that the water enters in the Cript not only during the rains but also from the perimeter walls of the Crypt and from the subsoil. In addition in the Crypt there is an high value of relative humidity in the indoor ambient.
The georadar analysis on the walls showed the presence of water until a depth of 3-
The adsorption from indoor ambient (as vapor water);
The capillarity (of liquid water from subsoil);
The downhill (of liquid water due to the rains).
The chemical and morphological analyses showed the presence of dehydrate Calcium sulphate (gypsum) on the frescoes that involved the exfoliations, efflorescence and detachments of frescoes from the plaster.
The presence of gypsum is due to the high content of water adsorbed from the indoor ambient (Relative Humidity higher than 90%) and adsorbed from the subsoil and perimeter walls.
Also the materials used to built the Cript influence the state of frescoes.
In fact from the analysis carried out, it was demonstrated that the entire cript was realized with pieces of various recovery stones: tuff, calcarenite, opus latericium, etc…
Each stone has a different behavior with water respect to the others, due to the different absorption capacity. In addition the deterioration of these materials (in particular the calcarenite) due to the water causes the production of gypsum as showed during the chemical analysis on the frescoes.
Following to these results the actions are to:
Promote the ventilation;
To limit the access of meteoric water;
Control the humidity and temperature;
To sanitize the air of indoor ambient.
In order to reach this goal it was suggested to realize a system to manage and control the climate in the Crypt. This goal could be reached using:
Air conditioning systems located close to the existing openings, so that the necessary air recharges and the disposal of the thermal load can be permitted.
Systems that can reduce water and water vapor content in the structure's materials to ensure acceptable hygrometer conditions.
Charge Neutralization Technology (CNT) systems for the neutralization of the electric charge of the water on the floor in contact with the walls (to avoid the capillary lift).
Sanitation system based on the use of a cold plasma in the gas phase, which when placed in the environment together with the air can reduce volatile organic compounds (VOCs), atmospheric particulate matter and many varieties of viruses, bacteria, molds and fungi .
After the realization of these systems it will be possible to provide an environment conducive to the preservation of frescoes in a non-
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