K. Van Balen

Nineteenth century hydraulic restoration mortars in the Saint Michael's Church (Leuven, Belgium) natural hydraulic lime or cement?

Abstract This research focuses on the characterization of nineteenth century hydraulic restoration mortars used in the Saint Michaels Church in Leuven (Belgium). The mortars were used as restoration mortars for weathered mortar joints. A historical study of old work descriptions and mineralogical, petrographical and chemical analyses have been used to characterize these hydraulic mortars. The different hydraulic phases are identified using petrographical analysis, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDX) and chemical analyses. Based on the presence of gehlenite (C2AS), the dominance of C2S, the large amounts of portlandite, the chemical analyses and on the historical sources, these hydraulic mortars are characterized as natural hydraulic lime mortars.

Atmospheric deterioration of ancient and modern hydraulic mortars

Different types of ancient and recent hydraulic mortars were collected from well-documented archaeological, historic and modern buildings in various geographical locations (urban, suburban, rural and maritime) of Italy, Spain and Belgium, representative of different environmental impacts, types and degrees of deterioration. A synthesis of the characteristics of the collected samples is presented, along with the identification of the formation products that occurred on the sample surfaces as a result of the reaction of the mortars with atmospheric pollutants. The analyses were performed by means of optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM-EDX) and ion chromatography (IC). The results obtained prove that sulphation processes takes place on hydraulic mortars, leading to gypsum formation on the external surface of the samples. Through the reaction of gypsum with the aluminate hydrate of the binder, ettringite formation was found to occur on a cement-based restoration mortar sampled in Antwerp.

Rilem TC 203-RHM: repair mortars for historic masonry. Performance requirements for renders and plasters

This article gives a summary of functional and performance requirements for renders and plasters for historic masonry (design, execution and maintenance). Specific attention has been paid to degradation effects, such as caused by salt crystallization and freeze–thaw cycling. Traditional as well as designed prefab mortars are considered for repair intervention.

Rilem TC 203-RHM: Repair mortars for historic masonry. Repair mortars for historic masonry: From problem to intervention: a decision

This article focuses on repair or replacement mortars for historical buildings. Both the decision process and questions arising are dealt with, in order to better define and illustrate technical requirements for mortars to be used for the repair or restoration of monuments and historic buildings (masonry mortars, plasters, renders…). The article summarizes a longer document, meant to help professionals in their decisions on the interventions, taking into account aspects, which are ranging from the ethics of restoration to the technical requirements.

Triaxial testing of historic masonry, test set-up and first results

In 1998 the Reyntjens Laboratory acquired a big size triaxial cell testing device for the testing of heterogeneous materials. The goal of the triaxial test set-up is to gather information about the material behaviour under a multi-axial stress state. In that it simulates the confining pressure of the surrounding material. In 1998 and 1999 the test set-up was developed. Meanwhile the first test results on the triaxial behaviour of lime mortar and masonry have been acquired. In the case of masonry cores, special attention is paid to the resulting biaxial yield-criterion. as this is of major importance for an assessment of the structural safety of the masonry. The study on lime mortar aims at determining its deformability in the case of a triaxial compression state. Especially the influence of the pore structure is evaluated. The research goal is the better understanding of the mechanical behaviour of ancient masonry, seeking for scientific explanation about the relative high mechanical strength of masonry built up with lime mortar that is considered to be a weak material. The test set-up is illustrated, the first test results and the resulting biaxial yield criterion for masonry based on cores are presented. Triaxial tests on both hydrated and hydraulic lime mortars as well as the mutual influence between the triaxial behaviour of the mortar and its pore structure are studied and discussed.

Quality management of interventions on historic buildings

The evaluation of the initial quality and long-term durability of an intervention on a historic building proves to be complex. On the one hand, technical and functional requirements can be defined which will lead to recipes and intervention methods. On the other hand, the heritage repair principles such as reversibility, compatibility and retreatability, should be respected. How are these aspects taken into account when defining an intervention in current practice? And how are they translated by the craftsmen into an actual intervention that meets their skills? The quality management approach presented in this paper was developed specifically for the cultural heritage sector and is based on a literature study and a study of current practice within Europe. Both literature and practice demonstrate that preservation of cultural heritage can be obtained by applying a planned preventive conservation approach and through a positive collaboration of all stakeholders. The proposed scheme will be confronted with the restoration of the fifteenth century enclosure of the Abbey of Tongerlo in order to understand its applicability in practice as a means for measuring the initial quality and long-term durability of interventions.

The stratified significance of a historic facade as a basis for a more durable conservation approach

Abstract In heritage conservation, a gap is often observed between the theory of conservation as a durable process that aims at the preservation of a historic building and the practice of restoration as a single intervention that aims at a fast and convincing result. This paper describes the proposed approach for the conservation of the main façade of the Shoemakers Chapel (in Dutch: Schoenmakerskapel) in Antwerp (Belgium), a listed monument since 1976. It serves as an example of how to develop a durable and realistic approach for the conservation of a sixteenth century façade. The basis for the conservation approach is the understanding that each intervention should take the stratified significance of the historic façade into account. In this paper, it will be shown how to combine a study of the façade from a technical point of view with an analysis of the façade as a carrier of cultural significance.

GEPATAR: A geotechnical based PS-InSAR toolbox for architectural conservation in Belgium

Ground displacements that cause structural damage to heritage buildings are precipitating cultural and economic value losses. The GEPATAR project (GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium) aims creating an online interactive geoinformation tool that allows the user to view and to be informed about the Belgian heritage buildings at risk due to differential ground movements. In the last decade, Persistent Scatterer SAR interferometry (PS-InSAR) has proven to be a powerful technique for analysing earth surface deformation. In order to identify the level of risk at national and local scales, this information is integrated with the Belgian heritage data by means of a GIS environment interactive toolbox and fusion modules. This paper presents a description of the methodology implemented in the project together with the case study of Saint-Vincent church, located in Zolder in a former colliery zone, for which damage is assessed.