I. Papayianni

Investigative methods for the characterisation of historic mortars—Part 1: Mineralogical characterisation

The mineralogical characterisation of historic mortars is performed for a number of reasons related to the conservation of traditional structures. The reasons for analysis and the questions posed during the conservation, repair or restoration of an old building determine the analysis methods that will be chosen. A range of mineralogical characterisation methods is available for the study of historic masonry mortars. These include X-ray Diffraction (XRD), Optical Microscopy, Scanning Electron Microscopy (SEM), Thermal and Infra-Red methods. Sample preparation is important; adequate separation of binder from aggregate is required for instrumental as opposed to microscopic investigation methods. An ordered scheme of analysis can be developed and is presented in flowchart form. It is difficult, and perhaps unwise, to analyse a mortar with only one method of characterisation. Corroboration of evidence of identification and quantification for mineralogical composition is best supported by a combination of methods, including chemical analysis methods. All methods of characterisation require qualified and experienced people to cary out the analyses.RésuméLa caractérisation minéralogique des mortiers historiques est exécutée pour des raisons différentes qui sont liées à la conservation des constructions traditionnelles. Les raisons de l’analyse et les questions posées lors de la conservation, la réparation ou la restauration d’une construction historique déterminent les méthodes d’analyse choisies. Une gamme de méthodes de caractérisation minéralogique est disponible pour l’étude des mortiers historiques de maçonnerie. Celles-ci comprennent la diffractométrie par rayon X (DRX), la microscopie optique, la microscopie électronique de balayage (MEB), les méthodes thermiques et infrarouge. La préparation de l’échantillon est importante: la séparation adéquate du liant et du granulat est obligatoire pour des méthodes instrumentales (comme les analyses chimiques), ce qui n’est pas le cas pour les méthodes d’investigation microscopiques. Il est difficile, et peut-être peu judicieux, d’analyser un mortier avec une seule méthode de caractérisation. Un schéma systématique relatif aux analyses à exécuter peut être développé et est présenté sous forme d’organigramme. Toutes les méthodes de caractérisation exigent du personnel qualifié et expérimenté pour exécuter les analyses.

Characterisation and damage analysis of old mortars

The scope of Rilem Committee TC167-COM is the characterisation of old mortars, with respect to their repair. For damage analysis of historic buildings, the characterisation of the old mortars may represent an essential part of the investigations. This statement can also be inverted, keeping in mind the scope of the committee and more specifically the second part ‘with respect to their repair’. It is essential to have knowledge of the condition of the old mortar and of the causes of any decay that has occurred (VAN HEES et al., 2000). The aim of this article is to underline the importance of knowledge on the factors that influence the way in which degradation of materials- and especially mortars in monuments - occurs. The most common forms of degradation of mortar in monuments, as well as the type of investigation, which is necessary to understand the cause of the damage, are described. On the basis of the assessed decay form and decay process, the most adequate repair method and the most suitable repair mortar can be chosen. The diagnosis of the damage is very often forgotten in practice, even though this is a fundamental step to guarantee a compatible and durable restoration. Such negligence can lead to major incompatibility problems in the case of repair mortar application. The approach discussed in this document can result in a better understanding of the causes of incompatibility and in guidelines for compatible repair mortars, based on the specific conditions of the individual monument. This article describes the approach, as proposed by Rilem TC167-COM .

Advances in chemical and physical properties of electric arc furnace carbon steel slag by hot stage processing and mineral mixing

Slags are recognised as a highly efficient, cost effective tool in the metal processing industry, by minimising heat losses, reducing metal oxidation through contact with air, removing metal impurities and protecting refractories and graphite electrodes. When compared to natural aggregates for use in the construction industry, slags have higher specific weight that acts as an economic deterrent. A method of altering the specific weight of EAFC slag by hot stage processing and mineral mixing, during steel production is presented in this article. The method has minimal interference with the production process of steel, even by limited additions of appropriate minerals at high temperatures. Five minerals are examined, namely perlite, ladle furnace slag, bauxite, diatomite and olivine. Measurements of specific weight are accompanied by X-ray diffraction (XRD) and fluorescence (XRF) analysis and scanning electron microscopy spectral images. It is also shown how altering the chemical composition is expected to affect the furnace refractory lining. Additionally, the process has been repeated for the most suitable mix in gas furnace and physical properties (FI, SI, LA, PSV, AAV, volume stability) examined. Alteration of the specific weight can result in tailoring slag properties for specific applications in the construction sector.

Mortars for intervention in monuments and historical buildings

The main problem in designing repair mortars for monuments and historical buildings is their compatibility with the old ones. Many parameters such as colour, texture, porosity, composition, size and type of aggregates as well as mechanical characteristics influence this compatibility. In the framework of many research projects sponsored by the Greek Ministry of Culture and European Committee, a great number of ancient mortars (from monuments of different historical periods) have been analyzed at the Laboratory of Building Materials of Aristotle University of Thessaloniki. Their composition, the physicochemical properties as well as their behaviour were found and studied systematically. Therefore, much experience has been accumulated. Based on this experience a long-term experimental study has been performed concerning the design and the quality of the repair mortars. In this paper the characteristics of a series of lime-based mortar compositions are presented. The research is focused on the effect of the binding system on the microstructure, the porosity and on the strength.

Cost-effective mixtures for concrete pavements

In concrete pavement construction large quantities of industrial by-products could be absorbed for the benefit of economy and sustainability, especially when large infrastructure projects are in progress. In Greece, a great amount of high calcium fly ash (12 million tons per year) and steel slag (2.5 million tons per year) is produced. The current utilization rate of the above by-products is relatively low. Before their utilization, the local industrial by-products should be tested and used properly to achieve optimum concrete mixtures for pavements. In this paper, local steel slag is used as aggregate in combination with a cement-fly ash binding system for the production of concrete mixtures whose strength ranges from 20 to 70 MPa. Apart from compressive strength, flexural tensile strength, elastic modulus of elasticity, fracture toughness, fatigue strength, and resistance to abrasion have been measured in a series of concrete compositions. Based on the results, it seems feasible to design and apply low-cost concrete mixtures for pavements, since they may contain a considerable amount of by-product for which the main cost is their transportation. The technical benefits related to their use in concrete are also presented.

Experimental study of nano-modified lime-based grouts

Grouts are fluid mixtures of binders with water, for the filling and strengthening of masonry or the consolidation and preservation of mortar stratification. In this paper, totally 15 compositions of lime-based grout mixtures containing admixtures and silica nano-particles were designed, manufactured and experimentally tested in order to evaluate their properties in fresh (fluidity, permeability, volume stability) and hardened state (shrinkage deformations, mechanical strength). Conclusive remarks were attained regarding the influence of silica nano-particles in grouts performance.

Grouts for Injection of Historical Masonries: Influence of the Binding System and Other Additions on the Properties of the Matrix

Grouting of historical masonries has been a widely used technique for regaining their integrity or strengthening them. Since cement-based grouts proved very strong, and in some cases destructive for these old masonries, grouts based on a lime-pozzolan binding system have been developed by researchers as an alternative, meeting compatibility issues required for repair interventions. In this paper, a number of grout compositions based on lime and other traditional binders are studied, with and without additions of limestone filler and nanoparticles of silica. In some, a small quantity of white cement (15 wt.%) was incorporated into the system. Apart from the different constituents of the binding system, the addition of admixtures was used for improving the properties of grouts. Rheological properties, such as fluidity, volume stability and penetrability of the grouts, were measured in the fresh state. Mechanical properties of dried grouts and grouted sand were checked. Volume changes due to drying shrinkage of grouts were recorded after demoulding and up to 28 days. The microstructure of the dried grouts of the control mixture and of that with silica nanoparticles was examined by stereoscope, image analysis, and DTA-TG methodology.

Feasibility Study and Criteria for EAF Slag Utilization in Concrete Products

The use of industrial byproducts in concrete applications is a scientific area of great interest over the past several years, and steel slags are acknowledged as having great potential for such use; however, the utilization rates are relatively low. The main barriers identified for this occurrence are failure to quantify benefits in terms of quality of the final product, environmental benefits, as well as cost reduction. The present research attempts to quantify these aspects for five different concrete applications examined as case studies. Laboratory-produced alternative concrete mixtures with steel slags are compared with ordinary reference concrete mixtures for their performance regarding mechanical characteristics and durability, environmental benefits using life cycle assessment, and cost estimation. The results show that there is great potential for the use of steel slag in concrete, but the benefits need to be determined for each specific use, since the values observed vary greatly depending on the application. Industrial pavement and heavyweight concretes seem to be the most favorable applications for steel slag, while the shotcrete and repair mortars examined benefited less from the use of slag.

Design and application of a data system for the comparative study of historic mortars

Mortars are among the first building materials used in constructions and have played a significant role in building technology’s evolution. A large number of mortar samples were systematically analyzed, leading to the need of a flexible data system in order to evaluate and comparatively study all results. This system allowed recording and classifying the data input (physico-mechanical, chemical characteristics), according to the mortar type (structural, renders-plasters, mosaic-mural substrates). With a specific toolbox all information could be easily sorted and comparatively - statistically evaluated, while the data input could be updated for future needs. The basic goal of the data system was to manage the information regarding historic mortars, but throughout its use it seems that a lot of other parameters could be also envisaged. It could therefore become a necessary tool for any scientist engaged to the field of restoration materials and techniques.

Survey of Repaired and Artificial Stones of the Archaeological Site of Pella Five Years After Application

An extensive restoration project was realized in the Archaeological site of Pella, in order to consolidate ancient stone remnants by filling them with mortar and manufacture artificial units of stone for anastylosis purposes. Samples of ancient stones were analyzed, regarding their morphological, physico-mechanical and chemical properties. Based on the evaluation of the analysis results, repair mortars were designed and tested for their compatibility with old stones. An in situ monitoring of the repair works took place, while samples for testing were taken from the site 2 and 5 years after the interventions. In this paper the results of the analysis of an adequate number of repaired and artificial stones are presented. The survey showed some cracks on few large stone units (100 \(\times\) 50 \(\times\) 30 cm) precast or cast in place. The analysis followed comprised color determination, measurement of compressive strength, modulus of elasticity and porosity properties. Microstructure examination was made, assisted by stereoscope and SEM-EDS, while soluble salt content and residual resistance to wetting-drying cycles were also carried out. The results were compared with the previous ones at earlier age, as well as with those of the authentic stone of Pella. Based on them, it seems that properly designed mortars are effective for consolidating or for completing missing parts of old stones without problems related with the existing microstructure and the resisting environmental cycling of the area. The characteristics of the designed repair mortars seem to be compatible with those of the old stones. The cracks appeared in some artificial stone units could be attributed to thermal load effects, as well as to lack of adequate curing.