Some mechanisms of microstructure weakening in high-porous calcareous stones

Certain kinds of stone used in buildings of archaeological, historic and architectural significance resemble aggregate of micrometre size, of weakly cemented, essentially calcite particles, containing numerous voids. Below the results are presented of an experimental investigation conducted for the purpose of determining the water-induced weakening effects on such stone. A calcarenite of the Sardinian Miocene (Cagliari pietra cantone) has been selected as model material for the investigation. Its microstructure is characterized by means of XRD, ESEM and MIP techniques. Compression strength, ultrasound propagation velocity and elongation provide an indication of the role played by various fluids (water, aqueous sodium chloride solution, kerosene) in weakening the interparticle bonding forces of the calcite grains. Permeability, pH and calcium ions concentration in the permeating water, on the other hand, point to the dissolution behaviour and hence weakening effects of water permeating through this type of microstructure.