Microscopic and macroscopic characterization of the porosity of marble as a function of temperature and impregnation

Sugaring marble in the Monumental Cemetery in Bologna (Italy): characterization of naturally and artificially weathered samples and first results of consolidation by hydroxyapatite

“…Even if the origins of marble bowing are rather controversial and multiple processes have been hypothesized to initiate it (e.g., the release of locked residual stresses [1,9], moisture presence [9] and acid rain attack [1]), a fundamental role of thermal excursions has definitely been assessed [1,6,9,10] and bowed marbles are certainly associated with new micro-crack development and porosity increase [9,10]. As in the case of sugaring, bowing affects both historical gravestones (as illustrated in Fig.…”

“…In particular, in the case of the Finland Hall, where the façade was entirely clad with thin Carrara marble slabs, a gradient in decohesion of calcite grains through the slab thickness was hypothesized as the cause of the dramatic marble bowing [1] that has caused the original slabs to be replaced [10]. Even if the origins of marble bowing are rather controversial and multiple processes have been hypothesized to initiate it (e.g., the release of locked residual stresses [1,9], moisture presence [9] and acid rain attack [1]), a fundamental role of thermal excursions has definitely been assessed [1,6,9,10] and bowed marbles are certainly associated with new micro-crack development and porosity increase [9,10].…”

“…This latter aspect further threatens marble durability, because, through the newly developed micro-cracks, clean and acid rainwater, salts-rich rising damp, as well as atmospheric gaseous pollutants, can penetrate into marble, thus worsening the related weathering phenomena (e.g., calcite dissolution, gypsum formation and salt crystallization) [5,7,[10][11][12][13]. Moreover, in the presence of moisture and/or liquid water, thermal weathering itself is accelerated, because, upon heating, water exerts a pressure against capillary pores, resulting in tensile stress inside marble [2,9,10,14,15].…”

“…Such alterations in the pore structure are, in turn, responsible for a reduction in strength and an increase in water absorption [5,10]. This latter aspect further threatens marble durability, because, through the newly developed micro-cracks, clean and acid rainwater, salts-rich rising damp, as well as atmospheric gaseous pollutants, can penetrate into marble, thus worsening the related weathering phenomena (e.g., calcite dissolution, gypsum formation and salt crystallization) [5,7,[10][11][12][13].…”

Thermal Effects on Compressive Strength of Local Limestone and Claystone

“…Porosity is further reduced by the precipitation of minerals into the remaining pore spaces as stated by Boggs, (2006). A comprehensive study of porosity can provide valuable information to determine whether a given type of natural stone is susceptible to thermal stresses or not (Malaga-Starzec, et al, 2006). The compressive strength results for the limestone and claystone cores after exposure to different temperatures as a function of porosity as shown in Table II.…”