Challenges in the Preventive Maintenance of Early 20th-Century Reinforced Concrete Architectural Sculptures

Abstract

“Twentieth-century building materials and construction techniques may often differ from traditional materials and methods of the past. There is a need to research and develop specific repair methods appropriate to unique types of construction.”

Approaches for the Conservation of Twentieth-Century Architectural Heritage, Madrid Document 2011, ICOMOS.

Natural deterioration caused by the ageing of the materials and their exposure to severe environmental conditions leads to a significant increase in the vulnerability of constructions. The conservation of reinforced concrete structures of the early 20th century brings challenges due to the specific characteristics of their construction processes. If at the structural level these processes are already somehow identified and linked to the systems of construction engineers such as Hennebique, Coignet, etc., at the level of decorative elements like ornaments, sculptures or others, their conservation deals with unknown techniques and requires greater care to maintain their authenticity and integrity.

Reinforced concrete, which is made of cement and steel, forms a material with a reduced lifespan when compared to natural and traditional construction materials such as stone or timber. Among other sources, the degradation of reinforced concrete is often caused by the corrosion of embedded steel, responsible for important losses of material which become particularly critical in sculptural elements.

When facing the need to make conservation interventions to preserve, rehabilitate, or restore degraded cultural heritage elements, several restrictions must be dealt with. Such restrictions are related to the safeguarding of the heritage’s cultural value and significance that must be weighed against safety and durability needs, as well as against the duration and budget constraints of the intervention. To assist the decision-making process about the type of interventions that can be carried out, an adequate balance of the several constraints must be sought. Therefore, in this paper, a two-step approach that can be integrated within the maintenance plan is proposed. The first step consists of a method to determine a case-by-case intervention index that gauges the referred criteria influencing the type of intervention. The referred index weighs the influence of several qualitative and quantitative criteria which are graded according to the characteristics of the cultural heritage element under analysis. The second step focuses on the development of maintenance indicators that can be used to assess the performance of the interventions that are carried out. This procedure was developed and implemented in the decision-making process related to the conservation of the decorative elements of a 20th-century building theatre in Portugal. A detailed analysis of the selected criteria for the intervention index and maintenance indicators is presented, as well as the advantages that might come from implementing the proposed procedure for the development of a sustainable conservation plan. A preliminary assessment of the maintenance indicators confirms that preventive measures decrease the number of repairs that are needed over time, meaning that the intervention index is correctly assessing the level of intervention required for a given decorative or sculptural element.