Conservation of Granitic Rocks and Application to Megalithic Monuments

Contract No : STEP-CT90-0110 EC

contribution : 895 000 EUROS

Starting date: 01 April 1991

Duration : 36 months

https://cordis.europa.eu/pub/eesd/docs/ka_review_eu_research_env_protection.pdf

Objectives: To improve knowledge of the degradation phenomena and to support the development of more effective procedures for the conservation of granitic materials, in general, and of the specific aspects related to the megalithic monuments, in particular.

Brief description of the Research Project: The technical work consists of in-situ inspections of monuments, identification and description of pathologies and selection of monuments for detailed studies. Laboratory work is carried out on material sampled directly in the monuments and in surrounding outcrops and existing quarries.

In-situ trials with non-destructive characterising methods are performed. Identification of differentially decayed zones, mapping of results and the development of a suitable technique for discriminating zones in different weathering stages in granitic rocks will lead to discussion on conservation operations.

To understand the multiple phenomena involved in stone degradation, some research on the basic principles of moisture and heat transport in porous media and their application to granitic rocks will be carried out. Laboratory studies will be conducted on the identification and description of irreversible phenomena in stones under current environment and service conditions, physical and mathematical modelling of effects induced by heat and fluids acting in the stone aiming at finding explanations for actual decay forms found in granitic rocks.

Biodegradation of granite rocks is also studied. The classification of colonising species and their habitats as well as the identification of existing signs of biotic attack and their interpretation in terms of physical and chemical transformations underwent by crystals, will be carried out. The efficacy of some selected biocide will be tested.

Stone treatment is an important part of this project. Technologies are developed for identification and characterisation of treatment products by physical and chemical means; the identification of transformation after curing “in vitro” and when applied to stones; the role of specific mineral components (feldspars and biotites); and the detection of different adhesion properties to these basic constituents of granites. The work also includes the characterisation of moisture behaviour inside the stones; evaluating the efficacy of some selected products; the definition of the most adequate criteria for performance evaluation and the assessment of durability of treated stones in extreme conditions (acid attack, salt crystallisation and freezing).

Investigations are carried out of construction technology used in megalithic monuments and acquisition of information about past interventions. Photographic and topographic survey of monuments and archaeological digs for investigating possible actions of the ground on the monuments are also performed.

The final results of this project were presented, jointly with those of the STEP project CT90- 0101 in the Workshop held in Santiago de Compostela (SP) on November 28-30 of 1994.