The restoration of Mercato Coperto external façades fits in interventions of landscape guardianship finalized to the safeguard and maintenance of the peculiar aspects of the urban landscape. It is also necessary to preserve, retrain and valorize the historical building.
The planned intervention is compatible with the area, producing positive effects on the environmental system and an improvement of the urban quality, the development of public spaces and, in an indirect way, the retraining of the historical city.
Among the principal causes of the external façades degradations, there is undoubtedly the water mechanical action and the meteoric running water with the aerosol effect of the frequent fogs, typical of this geographical area and of the habitat in which the building is situated. The two phenomena, accented by the freezing cycles during the winter season, have determined, in the time, a strong degradation of the interstitial fillers of the ashlars, allowing the water to infiltrate among the parts and to bait the formation of other pathologies of deterioration.
The particular location of the building inside the urban fabric in Ravenna, present the principal façade opened on a public plaza. The other façades are looking towards roads of average width. This orientation of the building has brought to a differentiation of each degradation, since the action of the water intensified by the presence of different drafts of air that skirt the surfaces depending on their orientation.
Moreover, the conformation of each wall module and the choice of the constituent materials (stone/decorative cement – tile - stone/decorative cement), each one defined by proper physical and chemical characteristics, has determined the geometry with which the different degradations are visible today. Such considerations have also confirmed from the diagnostic investigations effected in situ.
Before the design of the restoration project, it has been performed a careful and detailed diagnostic analysis, with the aim to individualize the degradations and the vulnerabilities which can compromise the correct functionality of the building and allow a suitable design of the restoration project.
The analysis of the façades has underlined the presence of different and characteristic morphologies of degradation:
- biological patina; strongly superficial deposit; chromatic alteration; black crust; efflorescence; erosions, scaling, traces of ferrous oxidation; fracturing / cracking; encrustation; lack; repainting; anthropogenic degradation (graffiti); loss of the mortar joint among bricks and ashlars.
After the individualization of the degradations, chemical - physics investigations on five materials samples withdrawn from the external façades were carried out from Doct. Roberto Mambelli: stone of Istria, black crust, fillers, brick, base of the paraste. On these elements have been effected observations with the stereomicroscopio and electronic microscope, X rays diffraction, analysis SEM - EDS with the electronic microscope and measures of the low pressure water absorption.
Also the interior elevations have been subject to a stratigraphical investigation with the objective to individualize the original cromia, the material typologies and the restitution of the construction processes that have interested walls, ceilings, metallic structures (pillars, capitals, trellis) and metallic window and door frames.
The intervention of restoration contains the characteristics of a conservative intervention: the surfaces object of the intervention have suffered, over time, different processes of degradation. Therefore the choice of the phases and the typologies of intervention, their chronology and the materials that will be used, hold in consideration the environmental problems which the materials will continue to be submitted to and the typology of the architectural element, with the purpose to improve its future maintenance.
[by Elisabetta Pizzari, Anna Claudia Cicognani]