Physico-mechanical characterization of the limestone used in Cartagena walls and a proposal for their restoration process

Abstract

The defensive walls of Cartagena de Indias, UNESCO cultural heritage since 1984, surround the historic centre of the Colombian City. Nowadays, the walled city represents the main tourist attraction of the Colombian Caribbean Sea and is also a world destination. Despite this importance, due to anthropogenic and environmental factors, the walĺs structure is highly deteriorated, with widely damaged sections at distinct risk of collapse, where replacement of deteriorated stone blocks is carried out without a technical criterion. The main purpose of this paper was to determine some criteria for selecting the most appropriate limestone to be used in the restoration process, based on empirical relations among ultrasound wave speed, mechanical strength, porosity, bulk density and elastic modulus of different limestones taken from five quarries located around the city. Analyzed physical properties showed that the current wall’s stone open porosity ranges between 18% and 25%, while the quarry stone range is between 7% and 44%. As for the quarry stone, the uniaxial compressive strength (UCS) variation varied from 1.88 MPa to 21 MPa. Results showed that in order to select the best stone to be used as a replacement, samples should have an ultrasound P-wave speed between 3844 and 4195 ms−1, and a dry mass between 223 and 251 g in a 5 cm cubic sample. A valid tool is proposed to the relevant authorities in the subject-matter to identify the right range of porosity and mass of the quarry stone to be employed in substitution of the deteriorated wall blocks, thus facilitating the restoration practices.