THE “PALOMBARO” (“SASSI” OF MATERA, ITALY): THE INTERACTION BETWEEN WATER AND CONSTRUCTION MATERIALS

The “Long Palombaro”, part of the network of underground structures and courtyards that was covered by the modern Piazza Vittorio Veneto above it, was once a fully functioning cistern up until the 19th Century. Previously there was an enormous cavity with water proof walls, limestone plastering and a series of dug-out and interconnected caves and tunnels, served by numerous, old, bell-shaped cisterns located underneath the piazza. This research is meant to identify the development phases and the building culture of the 16th Century cisterns and the strong relationship between this “water architecture” and the city. It is intended to make this great, carved architecture “usable” once again, even if other than its original use, preserving all its shape and material characteristics. The cistern represents an emblematic example of “negative” architecture, in which spaces are created by taking away material, contrary to “positive” architecture, where material is added. “Negative” architecture is created in successive phases of rock elimination and modelling, obliterating the material evidence of its building history. Here, remain the traces of carving on the vaulted ceiling intrados and on the rock walls, which, when not erased by finishing interventions, represent an important key in providing precious information about the carving techniques and the chronology of the relative building phases. In addition, this research is also aimed to make a cement mortar with an increased chemical resistance, capable of being used in cases of existing structure degradation, exposed to different environments, even aggressive. Moreover, the physical-chemical properties will be determined in order to optimize adhesion of the new mortar, as well as the physical, chemical and mechanical properties of mortar already in use. Experiments will mainly be based on analyses and comparison of mortar samples taken from specific spots in the Long Palombaro cistern and inert natural additive based mortars (e.g. sand, pozzolan and limestone). The first research phase will identify the most suitable constituents to be used to make mortars with good adhesion and permeability (of water and vapour), which should develop hydrous phases in different seasonal conditions and, most of all, potentially suitable to replace the pre-existing mortars.