The effects of wetting and drying, and marine salt crystallization on calcarenite rocks used as building material in historic monuments

Abstract

The results of a study of the effect of marine salt crystallization on the physical and mechanical properties of Plio-Pleistocene calcarenites cropping out in southern Italy are presented here. Owing to their workability, aesthetic appeal and availability, the calcarenites have been widely used as building stones in many historic monuments. Samples of medium-grained packstones and fine-grained packstones-wackestones were prepared for the salt crystallization test defined by EN 12370, using sea water instead of a 14% solution of Na2SO4 · 10H2O. To determine the effect of imbibition alone on the performance of the calcarenites, the same procedure was followed with distilled water without soluble salts. Microfabric analysis, evaluation of index parameters and grain-size distribution were carried out as well. Particular attention was given to pore-size distribution by mercury intrusion porosimetry (MIP), loss of weight and uniaxial compressive strength determined before and after the tests, and after every five cycles of complete immersion in sea water and distilled water. The results suggest that detailed information on fabric and pore network are indispensable to predicting the weatherability of rocks. Crystallization tests that involve the complete immersion of the samples in a saline solution are not effective for an understanding of the real importance of salt damage on soft and porous calcarenites owing to a significant incidence of imbibition in accelerating deterioration rates and in influencing patterns and intensity of weathering.

An Integrated Procedure to Assess the Stability of Coastal Rocky Cliffs: From UAV Close-Range Photogrammetry to Geomechanical Finite Element Modeling

“…However, with reference to coastal rock cliff, a faster and more intense weathering process of these calcarenite rocks results from the cyclic alternation of wetting and drying processes due to rainfall infiltration as well as from the marine salt crystallization following the contact with salt water. This is due to both the direct impact of the sea waves and the sea spray phenomena associated with the sea storms hitting the coast portion [36]. The sea water weathering is generally considered intense and aggressive on these calcarenite rocks, due to an effect of salt crystallization and bonding breakage, which results in a cementation reduction and a strength reduction of the rock in a relatively short-time period [36].…”

“…This is due to both the direct impact of the sea waves and the sea spray phenomena associated with the sea storms hitting the coast portion [36]. The sea water weathering is generally considered intense and aggressive on these calcarenite rocks, due to an effect of salt crystallization and bonding breakage, which results in a cementation reduction and a strength reduction of the rock in a relatively short-time period [36]. Therefore, instability processes triggered by weathering-induced rock degradation are relatively faster with respect to other areas characterized by calcarenite outcrops not affected by salt weathering [35,37].…”

“…This reflects the process of reduction of the cementation as induced by environmental weathering in carbonate rocks [35,36,52], which can develop both in the short-term, that is after calcarenite saturation, and in the long-term, due to cyclic drying-wetting processes as well as after contact with salt water. In the proposed modeling, no different weathering rates has been assumed along the cliff surface and a uniform weathering degree for the whole cliff has been accounted for.…”

Diagnosing decay: the value of medical analogy in understanding the weathering of building stones

“…In this way one process acts as an essential precursor to another, whereas others may act in parallel and some may even work synergistically to accelerate decay beyond the sum of their individual effects. Understanding the role and importance of stress inheritance does not, therefore, lie simply in listing all the stresses to which a stone has been subject, but in establishing the sequence of events and understanding the superimposed interactions between the various stress factors (Andriani & Walsh 2007).…”

Application of protective products to “Noto” calcarenite (south-eastern Sicily): a case study for the conservation of stone materials

“…Aggressive atmospheric environmental pollutants, freeze-thaw cycles and crystallization of salt solutions are the main causes responsible for the deterioration of stone materials exposed to outdoor conditions (Amoroso and Fassina 1983; Andriani and Walsh 2007;Cardell et al 2003;Del Monte et al 1981;Grossi and Brimblecombe 2007;Lopez-Arce et al 2009;Primerano et al 2000;Simao et al 2006;Turkington et al 2003;Viles and Gorbushina 2003;Zappia et al 1998). Sulfatation is a typical degradation process in urban environments, leading to the formation of gypsum-rich black crusts on surfaces sheltered from water and attacked by a SO 2 -polluted atmosphere (Fobe et al 1995;Schiavon and Zhou 1996).…”