L. Binda

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.

Definition of Structural Damage Patterns: A Structural Damage Atlas / Definition der Schadensmuster an Tragwerken: Ein Atlas der Tragwerksschäden

The paper proposes a Structural Damage Atlas. The atlas is to be part of the expert system MDDS (Monument Damage Diagnostic System) and is meant as a support for the identification and the explanation of structural damage. It contains a selection of well described and illustrated damage patterns, which may be formed by more than one damage type. They are ordered according to the most probable damaging process(es) causing them. The atlas serves as a reference for making sound hypotheses, which should be further supported by a thorough survey of the building, possibly tests, an analysis of the context in which the damage occurs and by information on the past and present state of the building.

Experimental Study on the Compatibility of a Polysiloxane Treatment with Substrates Loaded with Sodium Sulphate: Influence of the Physical Properties of the Substrates on the Salt Content Limit / Experimentelle Studie zur Verträglichkeit einer Polysiloxan-Behandlung mit einem porösen natriumsulfathaltigen Werkstoff: Einfluss der physikalischen Eigenschaften des Untergrundes auf den kritischen Salzgehalt

Within the framework of an EC program on the compatibility of salt with surface treatments (COST), crystallization tests were carried out on 20 different substrates (limestone, sandstone, brick, tuffeau, tuff and plaster) treated with a polysiloxane (Rhodia H224) or untreated. First, the samples were treated with the hydrophobic agent and the impregnation depth and product consumption were measured. Crystallization tests were carried out for each material using various initial salt contents. Both visual examination of the damage and weighing of loose materials (stone and salt) collected after the test (mass loss) were undertaken to provide qualitative and quantitative test evaluations. The influence of the protective treatment on the observed deterioration depends on the type of substrate. In general, treated samples result in worse spalling or flaking than that observed for untreated specimens. The treatment modifies the way the substrate dries and prevents surface efflorescence formation. But as salts crystallise deeper within the porous network, the treated material suffers other degradation phenomena and eventually, more damage.

Strukturelle Schäden in Mauerwerk: Beschreibung und Interpretation von Rissmustern, um die Schadensursache heraus zu finden / Structural Damage in Masonry, Description and Interpretation of Crack Patterns: Basis for Finding the Damage Causes

Before deciding on any repair technique for the conservation of damaged historic masonry structures a diagnosis based on experimental investigation and modelling has to be carried out. The first important step of this diagnosis is the survey and interpretation of the structural damages usually shown by a crack pattern. This operation is not always easy. In order to associate the damage symptoms to the damage causes it is necessary to describe the mechanical behaviour of masonry under different actions and to describe the possible causes of the structural damage. The aim of the paper is to define the basis for a structural damage atlas that will be further proposed as part of an expert system, MDDS, which has already been set up for the detection of physical damages to the masonry materials.