Bio-consolidation of the marble columns of the lions courtyard in the alhambra

Abstract

This study demonstrates the effectiveness of the MYXOSTONE M3P bio-consolidation treatment applied on the weathered marble of the columns of the Lions Courtyard of the Alhambra in Granada (Spain). The Lions courtyard is one of the most magnificent examples of the Nasrid dynasty and it is formed by galleries supported by 124 columns made of marble from Macael (Almeria, Spain). White marble from Macael has always been considered one of the most beautiful stones, for its colour and brightness, but it shows low durability towards thermal variations. The columns of the Lions Courtyard facing South are indeed extremely deteriorated, being scaling, swelling and material loss the most common deterioration patterns observed. Application of the MYXOSTONE M3P by means of poultice or spraying has shown to generate a tough bacterial cement of calcium carbonates nanoparticles embedded in bacterial exopolymeric substances that provides protection towards further weathering. This study also shows that the carbonatogenic activity of bacteria is still possible in low porous stones that present deterioration by-products such as gypsum, as well as surface deposits of clay minerals and previous (non-effective) alkoxysilane treatments. © 2018, University of Cantabria - Building Technology R&D Group. All rights reserved.