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Page 102 of 977 Results 1011 - 1020 of 9762

Natalia Rovella, Gianfranco Ulian, Daniele Moro, Giovanni Valdrè
Synthesis of geopolymers as sustainable materials for applications in Cultural Heritage

Recently, the studies on the possible applications of geopolymers as a sustainable alternative to the traditional concretes and consolidants increased considerably in many fields such as Cultural Heritage. The potentialities linked to their production concern the lower CO2 emissions, the possibility to reuse processing waste and the encouraging results in durability, chemical stability, and mechanical resistance. In this work, an industrial silt, a waste product of quarry rocks washing, was recycled in the synthesis of a series of Na-polysialate (siloxo) geopolymer concretes. The mechanisms of synthesis of metakaolin-based geopolymers were investigated, along with the influence of water content, described by the molar ratio H2O/Na2O, on the final product. The results obtained suggest that all the activating solutions effectively produced a reaction between the precursor and the activators, developing different geopolymers, but only the compositions with a low water content achieved the expected high compressive resistance qualities.

Martina Bernabale, Flavio Cognigni, Lorenzo Nigro, Marco Rossi, Caterina De Vito
Conventional and advanced techniques for archaeological diagnostic of iron artefacts

In this paper, an overview of corrosion processes on iron-based artifacts from Motya (western Sicily, Italy) is proposed. A review of the research contributions is given concerning two main topics: (i) the study of the interaction between iron weapons and the lagoon-like environment of Motya by means of spectroscopic and microscopic analyses. The results are compared with those obtained from the study of armors found in the Punic Necropolis of Lilybaeum (4th century BC, Sicily), which permit to define different corrosion models; (ii) the characterization of corrosion of iron nail (IV century BC) through a multi-modal and multi-scale approach using a X-Ray tomographic technique to get a comprehensive understanding of the structure, morphology, stratification, chemical composition and corrosion mechanisms.

Andrea Aquino, Stefano Pagnotta, Marco Lezzerini
Simulating weather degradation through heating of a calcarenite from Volterra, Italy: effects on the stone and its consolidation

The Panchina stone of Volterra, like that of Livorno, has been, since Etruscan and Roman times, a typical building material widely used in centralsouthern Tuscany. Here, Panchina stone varies in colour from reddish white to yellowish to cerulean, and the grain varies from fine to medium-coarse, depending on the extraction area. In this study, part of a broader study on building stones and their properties, we focus on the chemical-mineralogical and petrophysical characterization of the Volterra Panchina stone and its response to thermal stress. After the artificial ageing treatment by heating, various consolidating products were applied to investigate their effectiveness.

Gloria Zaccariello, Elena Tesser, Rebecca Piovesan, Giulia Gasperuzzo, Riccardo Simionato, Fabrizio Antonelli
Climate change and land subsidence in the frame of Venezia 2021 project: the deterioration of architectural stone materials

The overflowing of the canals and the flooding of the pedestrian walkways are the consequences of the well-known periodic large water inflow into the Venetian lagoon (high water or acqua alta). These phenomena lead the strong degradation of the stone buildings over time. With the aim to better understand the effects of high water and support the best actions and practices for preserving the cultural heritage of Venice by Municipality and Superintendences, thirty samples of five varieties of carbonate lithotypes were exposed to natural weathering in different Venetian areas and on Torcello island. The specimens were periodically monitored and compared with samples made of the same lithologies subjected to accelerated artificial aging tests. The results concerning the main deterioration morphologies observed on all the samples after three years of exposure are here presented and commented.

Giuseppe Alì, Francesco Demarco, Pierpaolo Antonio Fusaro, Carmelo Scuro
Numerical model for damage identification in brittle materials monitored by Acoustic Emission acquisition systems

A numerical method for damage identification in brittle materials is presented. The method is based on the time of arrival of the elastic wave, generated by the damage formation, to a group of sensors positioned on the boundary of a material sample. The equations of motion for the elastic waves are the starting point, including a body force term which accounts for the sudden formation of a crack. Then a discretization scheme for the 2D equations of elasticity is developed, which allows to obtained a suitable numerical model. Some numerical experiments are performed, to assess the validity of the method, reproducing the readings of some sensor positioned on the boundary of the sample. The location of the damage and the time of formation are identified by an appropriate nonlinear least square problem.

Giancarlo Bilotti, Domenico Bruno, Renato S. Olivito
Masonry arches reinforced with CFRP: an experimental and numerical investigation

Masonry constructions have received great attention from many researchers both from a theoretical and a practical point of view. This owing to the complex behaviour of the masonry material and the structural modelling problem of real constructions. Furthermore, this type of construction represents most historical and monumental constructions in the world, in terms of historical buildings, masonry arch bridges and monuments. However, these constructions are deteriorating over time after being subjected to a prolonged exposure to unfavourable environmental conditions. It therefore becomes important to plan their strengthening to preserve these cultural heritages. In this paper a numerical and experimental investigation of masonry arches is developed with an analysis of the effects of strengthening by means of advanced composite materials. The focus of the analysis concerns the effects on the strength and stiffness improvement of damaged masonry arches by strengthening with carbon fibre reinforced plastic. An experimental investigation was developed aimed to study the behaviour of damaged solid clay brick masonry arches strengthened with carbon fiber reinforced plastic. In addition, a finite element model of the structure is developed accounting for the effective geometry of the brick–mortar components of the masonry arch and of the reinforcement layer.

Luciano Ombres, Pietro Mazzuca, Marielda Guglielmi
Effect of the elevated temperatures on the mechanical behaviour of PBO-FRCM systems

Over the last two decades, fabric reinforced cementitious matrix (FRCM) materials started to be used as a strengthening system in a wide variety of structural applications, especially where their firerelated advantages may offer an alternative to traditional composite materials (e.g. FRP materials). However, there is a major gap in the knowledge of FRCM composites: the lack of information about their mechanical response at elevated temperature. The main objective of this paper is to provide further insights about the influence of elevated temperatures on the mechanical properties of a Polypara-pheny lene-benzo-bisthiazole (PBO) FRCM system. Direct tensile (DT) tests and single lap direct shear tests (DS) were performed respectively on PBO FRCM specimens and PBO FRCM-concrete prisms, for temperatures ranging from 20 ºC up to 300 ºC. Specimens were first heated up to the target temperature, and then loaded up to failure at ambient temperature. The results obtained show that both tensile and bond strength suffer relatively low reductions up to 200 ºC. For increasing temperature, the degradation of the mechanical properties was more pronounced: at 300 ºC, the reductions of tensile and bond strength were 65% and 40%, respectively.

Peixuan Wang, Gabriele Milani, Carmelo Scuro
Novel 3D distinct element limit analysis model for the seismic vulnerability evaluation of historical masonry pagodas of major importance in China

A new distinct element DEM limit analysis approach is presented and applied to the seismic vulnerability evaluation of an ancient masonry pagoda in China. The numerical model relies on the assemblage of infinitely resistant hexahedral elements and rigid plastic four-nodded interfaces, where all the internal dissipation lumps, constraining cracks to spread between adjoining elements. So, it is neither an upper bound nor a lower bound, but rather a DEM limit analysis. A masonry pagoda, Huqiu pagoda located in China, was selected as a case study to benchmark the model under the application of a seismic load. It is an octagonal masonry pagoda with a total of 7 floors and a height of 48.2m. The results show that the failure mechanisms found by limit analysis are basically vertical splitting with bending at the base. The results obtained by this research method are consistent with the actual behavior of masonry pagodas, which shows its suitability in direct applications by practitioners.

Domenico Camassa, Anna Castellano, Mariateresa Chiapperino, Aguinaldo Fraddosio, Mario Daniele Piccioni
Dynamic damage identification of masonry lighthouse by radar interferometry technique

Our work addresses the capability of the radar interferometry technique to identify the dynamic behavior of an historical masonry lighthouse. To achieve this goal, we have performed a campaign of ambient vibration tests for characterizing the dynamic properties of the San Cataldo's lighthouse located in Bari using ground-based radar interferometry. Moreover, the experimental results were used to calibrate a numerical approach for the assessment of structural damage. Indeed, by analyzing five different damage scenarios, the ability of the radar interferometry technique to identify each damage was investigated.

Rosario Morello, Andrea M. Gennaro, Laura Fabbiano
An Emissivity-based Approach to Assess the Integrity State of Archaeological Discoveries by Thermography

In this paper the authors propose an innovative technique to evaluate the integrity state of archaeological discoveries by using thermography. The proposed approach is based on the concept of emissivity. The case study is a marble bust of a woman that dates back to ancient Rome. The emissivity of the bust material has been evaluated by using a standardized procedure. To assess the integrity state of the sculpture, the environment temperature has been kept under control to allow the bust to reach thermal equilibrium. By evaluating pixel by pixel, the temperature deviation around the known equilibrium value, it has been possible to map the emissivity changes in the sculpture due to different conservation or decay states: alveolisation process, erosion, damages, deposition of iron oxide, etc. The proposed approach has allowed us to correlate the changes of emissivity with the integrity state of the sculpture. Preliminary studies on the bust provide interesting information about the deterioration from the original condition.

Page 102 of 977 Results 1011 - 1020 of 9762