Influence of the petrophysical and durability properties of carbonate rocks on the deterioration of historic constructions in Tebessa (northeastern Algeria)

Abstract

A thorough investigation of the weathering phenomena affecting a Byzantine Wall has been carried out. This Wall is a representative example of historic constructions in Tebessa (northeastern Algeria), in which limestone and carbonate tufa were the main materials used. Field investigations showed several weathering forms, including flaking, alveolisation, efflorescence, discolouration, fracturing, material loss and powdering. These weathering forms were mainly produced by salt action (gypsum and halite) and were related to the textural and petrophysical properties of the limestone and carbonate tufa. The quantification of the degree of deterioration using a Schmidt hammer revealed damage ranging from medium to severe. Petrophysical and durability properties were measured for both stone types extracted from ancient quarries. Pore structure, capillarity imbibition, P wave velocities and uniaxial compressive strength were used to characterise the petrophysical properties of the stones, and salt crystallisation tests were used to estimate their durability. These properties are closely linked to the stone microstructure. Carbonate tufas show excellent durability under salt crystallisation and a lower mechanical strength than limestone. Limestone, on the other hand, despite its low porosity and better mechanical strength, shows lower durability values. While micropores contribute to the relatively lower durability values of limestone, in tufa, macropores reduce the salt crystallisation effectiveness and improve the durability. According to our investigation, the Byzantine Wall requires urgent preservation measures. In the built heritage of Tebessa, limestone is expected be more prone to deterioration than carbonate tufa.