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ABSTRACT Fiber-reinforced cementitious matrix (FRCM) composites are a new category of composites recently proposed for seismic strengthening of historical masonry structures, to provide a more compatible solution compared with fiber-reinforced [...]

ABSTRACT Fiber-reinforced composites with inorganic matrix (FRCMs) have been recently proposed as a more compatible and durable route to strengthen masonry structures with respect to FRPs (fiber-reinforced polymers), but their [...]

ABSTRACT To increase the water resistance of gypsum-based stuccoes (i.e., pastes and mortars), the possible conversion of gypsum into less soluble calcium phosphates (CaP), by reaction with an aqueous solution [...]

ABSTRACT When consolidants are applied to porous stones, redistribution may occur inside the pore system after the treatment application, which influences their final penetration depth and performance. In this paper, [...]

ABSTRACT The durability of a new phosphate consolidant for limestone, based on formation of hydroxyapatite (HAP), was investigated in comparison with ethyl silicate (ES). Untreated, HAP- and ES-treated samples were [...]

ABSTRACT For consolidation of weathered carbonate materials (such as marble, limestone and lime-based mortars) no fully satisfactory treatment currently exists. In this paper, an innovative phosphate treatment was investigated as [...]

ABSTRACT Mechanical behaviour of old masonry may differ from the theoretical one to a great extent, hence it needs to be properly evaluated for quantifying the safety and serviceability of [...]

ABSTRACT In this paper an experimental study conducted on fired-day brick masonry triplets built with cement- and hydraulic lime-based mortars and subjected to artificial weathering cycles is presented. A cycle [...]

ABSTRACT Rising damp is one of the main problems affecting historical masonry structures all over the world, as it jeopardises materials integrity, inhabitants' health and performances of the building envelope. [...]

ABSTRACT Salt weathering is one of the most common deterioration mechanisms in porous materials and may lead to severe damage in buildings and artworks. In last decades, a lot of [...]

AB5TRACT The investigation of the electrical effects accompanying capillary water rise from ground in old masonries is of great practical interest, as such effects might be exploited for both measurement [...]

ABSTRACT A purposely designed experimental fixture for simultaneous and reliable monitoring of moisture, salts and spontaneous electrical polarization in masonry walls is proposed, based on the combined use of permanent [...]

High strength steel bars are widely used for the strengthening of masonry buildings, in particular to improve the connection between different structural elements, such as orthogonal walls and multi-leaf walls. A particular type of steel connector is the twisted bar, which due to its particular shape works as a self-threading screw, anchoring to the support material without any binder. The effectiveness of such technique mainly relies on the bond between the bar and the substrate, where adhesion, mechanical interlocking and friction play an important role. In this paper, a preliminary experimental study on pull-out behavior of twisted steel connectors inserted in brick units of different materials that can be commonly found in existing masonry buildings in Italy and in Europe is presented. Additionally, mechanical characterization of the materials is conducted to understand the influence of the compression strength and elastic modulus on the adhesion between the connector and the substrate. Preliminary results show that the pull-out response strongly depends on the mechanical properties of the substrate material.

In recent years, steel reinforced polymer (SRP) composites have emerged as a new technology for structural strengthening, and several researches have validated the effectiveness of SRP for masonry strengthening. Research has been carried out to study the bond behavior of SRP composites applied to a masonry substrate. However, how the moist and salt on masonry surface will affect bond, which is the weak link in real strengthening applications, is little known yet. This study aims at investigating the bond behavior of SRP composites applied to moist and salt-laden masonry blocks that were subjected to an artificial weathering protocol. Single-lap shear tests were conducted to determine the bond behavior, while ion chromatography provided the salts distribution of weathered specimens to interpret some results of the shear tests.

This paper presents the results of single-lap direct shear tests on steel reinforced grout (SRG) strips bonded to fired-clay brick and tuff masonry blocks. For this experimental campaign, fifteen masonry blocks were constructed and reinforced with SRG composite strips. Fired-clay bricks and tuff blocks herein employed were collected from demolished historical structures in Modena and Naples (Italy), respectively. Eight out of fifteen blocks were subjected to an artificial weathering procedure to induce salt crystallization, and therefore reproduce the degradation conditions that the buildings could be subjected to during their life. Bond behavior of unconditioned strengthened specimens (i.e. SRG-masonry joints) was compared with the behavior of conditioned joints. Salt distribution, open porosity, and water absorption of brick and tuff masonry units as well as of the SRG composite matrix were analyzed to understand if and how the salt crystallization influenced the adhesion between the SRG strip and the block.

For preservation of stones used in Cultural Heritage, affected by weathering processes that threaten their cohesion and mechanical properties, the application of consolidants is a common practice. However, available consolidating products generally exhibit some drawbacks that hinder their performance, in terms of either mechanical efficacy, compatibility with the substrate and/or durability. Ethyl silicate is currently the most widely used among stone consolidants; nevertheless, its reduced efficacy on calcitic substrates, together with its temporary hydrophobicity, its tendency to crack and its common formulation with volatile organic solvent, make the research for alternative consolidants for carbonate stones necessary. In this paper, a recently proposed new consolidation treatment based on the formation of hydroxyapatite inside the stone was tested on two different porous carbonate stones (Globigerina Limestone and Giallo Terra di Siena), and compared with TEOS-based treatments, frequently used for the consolidation of these lithotypes. The results show that the hydroxyapatite treatment exhibits a good efficacy in terms of mechanical properties and, compared to TEOS, it causes less pronounced alterations in open porosity and water transport properties. This makes the new treatment a potentially valid alternative to TEOS, especially in those situations where the possible presence of water behind the consolidated layer (e.g. in case of rising damp, condensation or infiltration) might threaten the durability of the consolidation intervention.

Soiling of external surfaces is an increasing issue for conservation of architectural heritage. Providing architectural surfaces with self-cleaning ability is one of the most promising routes of preventive conservation. To this aim, several methods have been proposed in the literature, based on the use of photocatalytic TiO2 nanoparticles, either directly applied onto the surfaces or incorporated in protective coatings. However, when nano-TiO2 is directly applied onto architectural surfaces, the particles are easily removed by rain. When TiO2 is incorporated in polymeric coatings, durability issues arise as well, because the photoactivity of TiO2 nanoparticles can promote degradation of the polymer. Here, we present an innovative alternative method, based on combination of TiO2 nanoparticles and hydroxyapatite (HAP). The incorporation of nano-TiO2 into an HAP coating protects the nanoparticles from leaching by rain, thanks to the chemical bonding between TiO2 and HAP, without diminishing their photoactivity. As a result, marble treated with HAP-TiO2 composites exhibits high self-cleaning ability and high durability, with results superior to those achieve by direct application of nano-TiO2 onto the surface, as frequently performed on site.

In this study, we investigated by FIB-SEM the microstructure of protective coatings formed by two inorganic treatments (namely, ammonium oxalate and ammonium phosphate solutions), with the aim of identifying the factors limiting the protective efficacy of the coatings and outlining possible improvement strategies. In the case of the oxalate treatment, the resulting layer of whewellite was found to contain vertical channels, which can allow water to reach the marble surface and trigger dissolution. Possible prevention of the formation of these channels by addition of a calcium source to the oxalate solution was attempted, but even micromolar additions led to rapid precipitation in the solution. In the case of the phosphate treatment, the resulting hydroxyapatite and octacalcium phosphate coating was found to be cracked and porous. To prevent cracks and pores, diminishing the ammonium phosphate concentration and adding ethanol to the solution were found to be effective strategies, as cracks were prevented and pores were reduced almost to zero. The resulting protective efficacy of the coating was found to be significantly improved, although still not perfect.

This study presents an intermingled fractal model capable of simulating the porous microstructure of natural stones used in historical buildings. The developed model is aimed at predicting, by an analytical approach, the sorptivity of these materials. To verify the actual ability of the proposed method to predict stone sorptivity, in this study the intermingled fractal units model was applied to eight types of natural stones. The results are in very good agreement with sorptivity values obtained by experimental tests on the investigated stones. Compared to other analytical formulas proposed in the literature for predicting the sorptivity of porous materials, the newly proposed method better matches with the experimental results, and this can be attributed to that fact it takes into consideration the whole pore size distribution of the analyzed material, rather than the average pore radius only. Thanks to the proposed method, the sorptivity of natural stones used in historical buildings can be calculated from their pore size distribution determined by MIP, which, contrary to standard tests for sorptivity determination, only requires small and irregular samples. [ABSTRACT FROM AUTHOR]