Intrinsic factors determining the physical behaviour and durability of the Miocene sandstones used to build the Zaghouan-Carthage aqueduct (Tunis)

The present paper addresses the relationship between the intrinsic factors, physical behaviour and durability of Miocene Age sandstone used to build Tunisian Heritage Monuments, and more specifically the Zaghouan-Carthage aqueduct. A petrographic study (optical microscopy and mercury intrusion porosimetry) was conducted to characterise the porous system of the rock. Stone hydric behaviour was also determined by finding vacuum saturation, desorption, capillary and water vapour transmission. Finally, mechanical strength (compressive strength, abrasion resistance) and durability (via accelerated sodium sulfate crystallisation ageing) were also found. The results obtained were indicative of good hydric performance due to the macroporous nature of the stone and the connectivity of its porous system. This rock was also found to have very low mechanical strength due to its scant lithification, making it particularly susceptible to salt weathering. It was also observed to be highly resistant to chemical alteration, given the absence of chemically unstable minerals in its composition. The durability of the material was consequently found to depend directly on the presence or absence of salts in the monument.