Vasiliki Pachta

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.

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.

Content and topography of salts in historic mortars

Salt crystallization induces deterioration phenomena to masonry materials especially under favorable conditions which depend on a triple-fold system of factors: the salts’ nature, the materials’ type and structure and finally the environmental aspects. Among the oldest building materials, the lime-based mortars have been used for different construction purposes and exhibited admirable durability. The present paper presents the results of a statistical process of more than 1000 mortars from different monuments and historic periods in an effort to correlate salt formation with macroscopic and microscopic properties. Instrumental analysis of liquid ion chromatography has been applied for recording the type of soluble salts found into the mortar’s structure; moreover, the location and the form of crystallization as well as the mechanical and physical properties of these mortars have been determined. The evaluation of the combined analysis shows that lime-based mortars sustained a significant load of salts without being destroyed.

Evolution of Building Materials and Philosophy in Construction: A Process of Digitalization and Visualization of the Accumulated Knowledge

The long-term research on the constructional materials and techniques of monuments and historic buildings, allowed the accumulation of significant knowledge which could be further disseminated. The masons of antiquity followed principles in designing and building, established by their intuition and experience. The selection of raw materials, the way they upgraded them in constructing foundations, walls, domes, is still remarkable. In the paper, a process of using digital technology tools for making knowledge acquisition attractive is presented. By developing a specific platform, all relevant scientific knowledge can be sorted, while with a series of digital applications, the diachronic principles of construction, the ancient technology and the achievements of the past can be exploited in a friendly and interactive environment. By this way it is expected that the values of building philosophy in the context of safety, sustainability and economy will be forwarded to new generations.