Publisher Summary This chapter describes the research conducted to study the main characteristics... more Publisher Summary This chapter describes the research conducted to study the main characteristics that influence the changes in highly porous stone materials and the parameters that most clearly quantify this degradation. Two blocks of quarry carparo (highly porous calcarenite) from Casalabate and Gallipoli were used. The laboratory study was carried out by examining their characteristics before and after artificial aging. Observations by optical microscopy, X-ray diffraction (XRD) analyses, porosimetric measurements, permeability and evaporation tests, absorption by capillarity and immersion tests, and measurement of ultrasonic wave velocity were carried out on samples from quarries. The same samples were then exposed to artificial aging with sodium sulfate, which effectively produced deterioration comparable with the "in situ" calcarenite stones. All the measurements that were carried out before aging procedure were repeated on the samples. On examination of the results obtained, the porosimetric analysis and the petrographic analysis on thin section provided best conclusions in understanding the diverse reaction of materials to this type of weathering. From the analyses, it can be concluded that pore size distribution and textural characteristics of cement are not quantifiable to the deterioration measurement because of its superficial location. On the contrary, the most significant parameter for the evaluation of durability is weight variation because of loss material.
The paper presents a new procedure to assess the compressive strength of regular masonry starting... more The paper presents a new procedure to assess the compressive strength of regular masonry starting from results of non-destructive ultrasonic pulse velocity tests (UPV) on the constituent materials. The procedure has been calibrated on a soft calcarenitic stone used in the heritage masonry of Southern Italy, and starts from the knowledge of the regression between UPV and the compressive strength (UCS) of the material, determined by means of a wide experimental campaign on different varieties of quarry samples. Through an improved cross validation technique, the proposed method allows to estimate the compressive strength of new samples by making only non-destructive measurements without the need to conduct compression tests. The quality of the procedure was assessed both at the block scale and at the wall scale by comparing the estimated results with those obtained experimentally. In particular, the experiments were performed using new quarry stone blocks and blocks taken from existing walls of two ancient buildings during restoration works. The proposed method has proven to be reliable for the investigated material and it is easy to apply also for other materials as soon as it is possible to carry out a preliminary calibration in the laboratory, which allows knowing the UPV-UCS relationship over a wide range of strengths. Keywords Non destructive test Á Mechanical characterization of masonry Á Soft building limestone Á Cross validation procedure Á Predictive performance of regression models Á Ultrasonic pulse velocity
The tobacco industry in Puglia has been for about a century the main economic resource for the fa... more The tobacco industry in Puglia has been for about a century the main economic resource for the farmers and the dealers. The first processing with Levantine tobacco began in Terra d'Otranto (the current provinces of Lecce, Brindisi and Taranto) between the late XIX and early XX centuries and were linked to the Agricultural Consortium of the Capo di Leuca territory (from 1938 Acait-Società Cooperativa Agricola Industriale del Capo di Leuca). Acait was the first cooperative agricultural consortium of the Terra d'Otranto born in Tricase (Lecce, Italy) in December 1902. In 2003 the municipality of Tricase acquired the historic factory, considered a "monument" of the industrial heritage of southern Italy, as a peculiar economic, social and human testimony of the territory. In 2018, the southern part of building was affected by a collapse. Given the high value of this industrial heritage artifact, a restoration project of the entire building was promoted. The paper illustrates some results of an ongoing study that combines data from historical-archival research with an architectural survey campaign and diagnostic analyses on the state of conservation.
Several lime mortars for the repair of painted plasters of the rock cut church of Ss. Pietro and ... more Several lime mortars for the repair of painted plasters of the rock cut church of Ss. Pietro and Paolo in Matera were studied. They were designed taking into account both aesthetic criteria that need to be fulfilled in the field of paintings restoration, and physical-mechanical compatibility with the original materials on site, i.e. the pre-existing plasters and the supporting rock. Mixes with calcareous and silica aggregates, based on different grain size proportions, were prepared for filling missing portions of the original painted plaster. The effects of the mineralogical nature and size of the aggregates on the characteristics and properties of the mixes were investigated in relation to the microstructure, physical-mechanical features and resistance to salt ageing. At the end of the experimental campaign, the overall performances were evaluated.
6th International Meeting on Retouching of Cultural Heritage. RECH6
This study was carried out during the ICR conservation project involving two of the mural paintin... more This study was carried out during the ICR conservation project involving two of the mural paintings of the Saint Peter and Paul’s hypogeum in Matera. Retouching mural paintings preserved in such a peculiar environment as hypogea is not an ordinary operation. In these contexts, relative humidity approximating to 100% makes hygroscopic materials less durable, favouring biological growth on them. In addition, severe climatic conditions can lead to a fast degradation of retouching materials. Watercolours, extensively employed for retouching mural paintings, are not completely recommendable in such humid environments, so a research was planned to find a compatible and alternative binding media. A study was carried out on laboratory samples to select the most suitable binding media among the following: two synthetic resins, Laropal A81 and Regalrez 1094, and two natural products, Funori and arabic gum. Each binder was blended with two different pigments. For each binder four different di...
Approach to the study of conservation of historical masonry mortars by means of the correlation b... more Approach to the study of conservation of historical masonry mortars by means of the correlation between porosimetry and penetrometric test. First results Angela Calia1; Domenico Liberatore2; Nicola Masini3 1 CNR-IBAM (Istituto per i Beni Archeologici e Monumentali), Lecce, Italy; 2 University la Sapienza, Rome, Italy; 3 CNR-IBAM (Istituto per i Beni Archeologici e Monumentali), Potenza, Italy
The ultrasonic pulse velocity (UPV) method can be conveniently used for non-destructive testing o... more The ultrasonic pulse velocity (UPV) method can be conveniently used for non-destructive testing of physical-mechanical properties of the stones within historical masonry, as well as to check the state of damage and microcracking. Before to proceed with in situ measurements, it is important to assess the contribution that both intrinsic characteristics of the stones and external factors may give to the ultrasonic response. In this work the effect of different wave frequencies, sample geometry and application of a compression load on the response of a natural stone to UPV test has been investigated. An extensive experimental campaign in laboratory conditions was carried out on a soft limestone, used in the historical building heritage of the Southern Italy. A negligible UPV dispersion was found at the used frequencies of 1 MHz, 120 and 55 kHz when a compression load was not applied; the measured velocities were found to be influenced by the stone inhomogeneity rather than by the sample size. They showed a slight decrease and still negligible dispersion under load up to the visible damage. Dispersion increased with the cracking progression. This indicates that enhanced capability of UPV, in checking material quality and damage conditions, can be obtained by combining the use of different wave frequencies.
A colloidal route was exploited to synthesize TiO2 anisotropic nanocrystal rods in shape (TiO2 NR... more A colloidal route was exploited to synthesize TiO2 anisotropic nanocrystal rods in shape (TiO2 NRs) with a surface chemistry suited for their dispersibility and processability in apolar organic solvents. TiO2 NRs were dispersed in chloroform and n-heptane, respectively, and the two resulting formulations were investigated to identify the optimal conditions to achieve high-quality TiO2 NR-based coatings by the spray-coating application. In particular, the two types of TiO2 NR dispersions were first sprayed on silicon chips as a model substrate in order to preliminarily investigate the effect of the solvent and of the spraying time on the morphology and uniformity of the resulting coatings. The results of the SEM and AFM characterizations of the obtained coatings indicated n-heptane as the most suited solvent for TiO2 NR dispersion. Therefore, an n-heptane dispersion of TiO2 NRs was sprayed on a highly porous limestone—Lecce stone—very commonly used as building material in historic co...
Over the last few years, photocatalytic titanium dioxide coatings have been explored in laborator... more Over the last few years, photocatalytic titanium dioxide coatings have been explored in laboratory conditions to create building materials with self-cleaning and depolluting abilities. Assessing the performances of the photocatalytic surfaces under real conditions may provide basic knowledge to evaluate the potential of real applications of TiO 2 coatings in buildings. In this study, the performance of photocatalytic limestone surfaces obtained through coating with waterdispersed TiO 2 nanoparticles were investigated in an urban environment. Coated and uncoated samples were exposed to an urban site for one year. Before the exposure and periodically afterwards, optical microscopy observations, colour and contact angle measurements were performed on the sample surface. At the end of the exposure period, samples underwent a capillary water absorption test and self-cleaning efficiency was evaluated by a Rhodamine B photodegradation test. Ti and soluble fraction amounts on the sample surfaces were determined by X-ray Fluorescence (XRF) and ion chromatography, respectively. The overall results showed the TiO 2 coating was better able to preserve the surface colour properties early after exposure. After eight months, this effect was lost and the self-cleaning efficiency was reduced to negligible final rates. No clear wettability results and no meaningful capillary behaviour were recorded. A decrease of the photocatalytic activity was due to both partial titania loss and deactivation phenomena. The role of soluble salt ions either adsorbed from the environment or produced by the photocatalytic abatement of pollutants was recognized in the deactivation of the photocatalysts and their accumulation deserves attention for possible stone damage risk implications.
Field study of hydrophobic and selfcleaning TiO 2 NPs/fluoropolymer stone coatings • On the long ... more Field study of hydrophobic and selfcleaning TiO 2 NPs/fluoropolymer stone coatings • On the long run TiO 2 NPs did not interfere with the hydrophobicity of the polymer. • TiO 2-based coatings preserved cleaner surface than the mere fluoropolymer coating. • Photocatalytic efficiency reduced depending on the TiO 2 amounts in the mixtures. • TiO 2 embedded in the polymer limited salt ion loads absorbed by NPs on the surface.
h i g h l i g h t s UPV, Rebound and compressive microcore tests for stone masonry strength estim... more h i g h l i g h t s UPV, Rebound and compressive microcore tests for stone masonry strength estimation. Statistical evaluation of accuracy of each test measurements is performed. Multivariable methods improves correlation models between direct and indirect tests. Iterative cross-validation is effective in evaluating model predictive performances. Combined UPV and microcore strength tests gives the best estimation of UCS.
Rod-shaped TiO 2 nanocrystals (TiO 2 NRs), capped by oleic acid molecules (OLEA), were synthesize... more Rod-shaped TiO 2 nanocrystals (TiO 2 NRs), capped by oleic acid molecules (OLEA), were synthesized with controlled size, shape and surface chemistry by using colloidal routes. They were investigated for application as coating materials for preserving architectural stone of monumental and archaeological interest, in consideration of their self-cleaning and protection properties. For this purpose, two different deposition techniques, namely casting and dipping, were tested for the application of a nanocrystal dispersion on a defined stone type, as a relevant example of porous calcarenites, namely the Pietra Leccese, a building stone widely used in monuments and buildings of cultural and historic interest of the Apulia region (Italy). The physical properties of the stone surface were investigated before and after the treatment with the prepared nanostructured materials. In particular, colour, wettability, water transfer properties and stability of the coating were monitored as a function of time and of the application method. The self-cleaning properties of the TiO 2 NRs coated surfaces were tested under simulated and real solar irradiation. The obtained results were discussed in the light of the specific surface chemistry and morphology of TiO 2 NRs, demonstrating the effectiveness of TiO 2 NRs as an active component in formulations for stone protection.
Coating with nanostructured Titanium dioxide is able to enhance natural stone surface with self-c... more Coating with nanostructured Titanium dioxide is able to enhance natural stone surface with self-cleaning and depolluting abilities; nonetheless, the durability of the coatings is a crucial issue to be assessed in relation to their potential for use in the context of the building heritage. In this paper, the resistance of coatings applied on a compact and a soft limestone, which differ in roughness, porosity and cohesion features, has been investigated. A peeling and a water impact test were performed and their effect on the coated surface was evaluated as film loss by qualitative/quantitative ESEM-EDS analyses. Self-cleaning effectiveness was assessed by performing a photodegradation test of Rhodamine B. Crack-free and conformable films showed a good anchorage to both limestones; after the durability tests the coated surfaces exhibited almost unchanged Ti/Ca ratios and self-cleaning efficiencies. Large adhesion failures and decreased Ti amounts were recorded where coatings were fissured; they especially occurred on the surface of the compact limestone, along with a reduced self-cleaning ability. High surface roughness accounted for a better adhesion of both crack-free and fissured films to the soft limestone, but some erosion of the coated surface, which affected this friable stone under the water impact, compromised their preservation. Nonetheless, good self-cleaning performances were still provided due to the retention of nanoparticles under the surface. The overall results support that preservation of nanostructured TiO 2 coatings on the stone surface depends on the inherent characteristics of both films and supports; durability of the stone itself can play an important role.
Abstract In this work Ultrasonic Pulse Velocity (UPV), Schmidt Hammer Rebound (SHR) test and stre... more Abstract In this work Ultrasonic Pulse Velocity (UPV), Schmidt Hammer Rebound (SHR) test and strength assessment on microcores (UCS m ) and standard cubic samples (UCS c ) were used to detect the uniaxial compressive strength of stone masonry units. The analysis of the variability of the measurements allowed to investigate the significance of each test to differentiate the masonry blocks. The latter was evaluated by a Variability Index (VI), as the ratio between the variances at block scale and among the blocks. VI was found higher for UCS c and UPV than for UCS m and SHR measurements. A regression analysis aimed to the correlation of uniaxial compressive strengths evaluated by conventional destructive test on stone cubes with the other test results. The findings showed a good linear correlation among UCS c and UPV values (R 2 = 0.83), thus supporting the reliability of UPV to screen the masonry units and to estimate their uniaxial compressive strength. The correlation of UCS c with UCS m was reasonable (R 2 = 0.76), while it was low with SHR results; some limits related to the use of SHR and UCS m tests are also discussed.
Bulletin of Engineering Geology and the Environment, 2015
Many building materials have been functionalized to achieve photocatalytic properties, namely sel... more Many building materials have been functionalized to achieve photocatalytic properties, namely self-cleaning and depolluting abilities, through the application of photocatalytic TiO2 nanoparticles to those materials. These nanoparticles are able to preserve building façades by blocking the deposition of airborne particulates in polluted urban environments, and they are able to purify the air, thus benefiting the environment. In this study, the application of nanostructured TiO2 as a photoactive coating on two types of natural stone was investigated. A TiO2 sol obtained by sol–gel synthesis followed by hydrothermal processing was applied via spray deposition onto a compact limestone and a highly porous calcarenite. The effects of this coating on some basic properties of the stone, such as its color and water absorption, and the photocatalytic effectiveness of the coated surface were then studied. Scanning electron microscopy and energy-dispersive X-ray spectroscopy showed that the coating presented a uniform morphology on both types of stone, with the TiO2 nanoparticles penetrating <1 µm into the stone. The coating was found to be compatible with the properties of the investigated types of stone. Colorimetry indicated that the change in the color of the stone due to the coating was negligible. Measurements of the static contact angle and the results of the capillary water absorption test showed that photoinduced superhydrophilicity did not increase the amount of the water absorbed by the coated stone. A photodegradation test of rhodamine B demonstrated the self-cleaning ability of the coating on both types of stone. Conversely, the photocatalytic effectiveness of the coating—as measured by a nitrogen oxide abatement test—was found to be higher for the porous calcarenite than for the compact limestone, and to depend on the porosity and roughness of the substrate.
Publisher Summary This chapter describes the research conducted to study the main characteristics... more Publisher Summary This chapter describes the research conducted to study the main characteristics that influence the changes in highly porous stone materials and the parameters that most clearly quantify this degradation. Two blocks of quarry carparo (highly porous calcarenite) from Casalabate and Gallipoli were used. The laboratory study was carried out by examining their characteristics before and after artificial aging. Observations by optical microscopy, X-ray diffraction (XRD) analyses, porosimetric measurements, permeability and evaporation tests, absorption by capillarity and immersion tests, and measurement of ultrasonic wave velocity were carried out on samples from quarries. The same samples were then exposed to artificial aging with sodium sulfate, which effectively produced deterioration comparable with the "in situ" calcarenite stones. All the measurements that were carried out before aging procedure were repeated on the samples. On examination of the results obtained, the porosimetric analysis and the petrographic analysis on thin section provided best conclusions in understanding the diverse reaction of materials to this type of weathering. From the analyses, it can be concluded that pore size distribution and textural characteristics of cement are not quantifiable to the deterioration measurement because of its superficial location. On the contrary, the most significant parameter for the evaluation of durability is weight variation because of loss material.
The paper presents a new procedure to assess the compressive strength of regular masonry starting... more The paper presents a new procedure to assess the compressive strength of regular masonry starting from results of non-destructive ultrasonic pulse velocity tests (UPV) on the constituent materials. The procedure has been calibrated on a soft calcarenitic stone used in the heritage masonry of Southern Italy, and starts from the knowledge of the regression between UPV and the compressive strength (UCS) of the material, determined by means of a wide experimental campaign on different varieties of quarry samples. Through an improved cross validation technique, the proposed method allows to estimate the compressive strength of new samples by making only non-destructive measurements without the need to conduct compression tests. The quality of the procedure was assessed both at the block scale and at the wall scale by comparing the estimated results with those obtained experimentally. In particular, the experiments were performed using new quarry stone blocks and blocks taken from existing walls of two ancient buildings during restoration works. The proposed method has proven to be reliable for the investigated material and it is easy to apply also for other materials as soon as it is possible to carry out a preliminary calibration in the laboratory, which allows knowing the UPV-UCS relationship over a wide range of strengths. Keywords Non destructive test Á Mechanical characterization of masonry Á Soft building limestone Á Cross validation procedure Á Predictive performance of regression models Á Ultrasonic pulse velocity
The tobacco industry in Puglia has been for about a century the main economic resource for the fa... more The tobacco industry in Puglia has been for about a century the main economic resource for the farmers and the dealers. The first processing with Levantine tobacco began in Terra d'Otranto (the current provinces of Lecce, Brindisi and Taranto) between the late XIX and early XX centuries and were linked to the Agricultural Consortium of the Capo di Leuca territory (from 1938 Acait-Società Cooperativa Agricola Industriale del Capo di Leuca). Acait was the first cooperative agricultural consortium of the Terra d'Otranto born in Tricase (Lecce, Italy) in December 1902. In 2003 the municipality of Tricase acquired the historic factory, considered a "monument" of the industrial heritage of southern Italy, as a peculiar economic, social and human testimony of the territory. In 2018, the southern part of building was affected by a collapse. Given the high value of this industrial heritage artifact, a restoration project of the entire building was promoted. The paper illustrates some results of an ongoing study that combines data from historical-archival research with an architectural survey campaign and diagnostic analyses on the state of conservation.
Several lime mortars for the repair of painted plasters of the rock cut church of Ss. Pietro and ... more Several lime mortars for the repair of painted plasters of the rock cut church of Ss. Pietro and Paolo in Matera were studied. They were designed taking into account both aesthetic criteria that need to be fulfilled in the field of paintings restoration, and physical-mechanical compatibility with the original materials on site, i.e. the pre-existing plasters and the supporting rock. Mixes with calcareous and silica aggregates, based on different grain size proportions, were prepared for filling missing portions of the original painted plaster. The effects of the mineralogical nature and size of the aggregates on the characteristics and properties of the mixes were investigated in relation to the microstructure, physical-mechanical features and resistance to salt ageing. At the end of the experimental campaign, the overall performances were evaluated.
6th International Meeting on Retouching of Cultural Heritage. RECH6
This study was carried out during the ICR conservation project involving two of the mural paintin... more This study was carried out during the ICR conservation project involving two of the mural paintings of the Saint Peter and Paul’s hypogeum in Matera. Retouching mural paintings preserved in such a peculiar environment as hypogea is not an ordinary operation. In these contexts, relative humidity approximating to 100% makes hygroscopic materials less durable, favouring biological growth on them. In addition, severe climatic conditions can lead to a fast degradation of retouching materials. Watercolours, extensively employed for retouching mural paintings, are not completely recommendable in such humid environments, so a research was planned to find a compatible and alternative binding media. A study was carried out on laboratory samples to select the most suitable binding media among the following: two synthetic resins, Laropal A81 and Regalrez 1094, and two natural products, Funori and arabic gum. Each binder was blended with two different pigments. For each binder four different di...
Approach to the study of conservation of historical masonry mortars by means of the correlation b... more Approach to the study of conservation of historical masonry mortars by means of the correlation between porosimetry and penetrometric test. First results Angela Calia1; Domenico Liberatore2; Nicola Masini3 1 CNR-IBAM (Istituto per i Beni Archeologici e Monumentali), Lecce, Italy; 2 University la Sapienza, Rome, Italy; 3 CNR-IBAM (Istituto per i Beni Archeologici e Monumentali), Potenza, Italy
The ultrasonic pulse velocity (UPV) method can be conveniently used for non-destructive testing o... more The ultrasonic pulse velocity (UPV) method can be conveniently used for non-destructive testing of physical-mechanical properties of the stones within historical masonry, as well as to check the state of damage and microcracking. Before to proceed with in situ measurements, it is important to assess the contribution that both intrinsic characteristics of the stones and external factors may give to the ultrasonic response. In this work the effect of different wave frequencies, sample geometry and application of a compression load on the response of a natural stone to UPV test has been investigated. An extensive experimental campaign in laboratory conditions was carried out on a soft limestone, used in the historical building heritage of the Southern Italy. A negligible UPV dispersion was found at the used frequencies of 1 MHz, 120 and 55 kHz when a compression load was not applied; the measured velocities were found to be influenced by the stone inhomogeneity rather than by the sample size. They showed a slight decrease and still negligible dispersion under load up to the visible damage. Dispersion increased with the cracking progression. This indicates that enhanced capability of UPV, in checking material quality and damage conditions, can be obtained by combining the use of different wave frequencies.
A colloidal route was exploited to synthesize TiO2 anisotropic nanocrystal rods in shape (TiO2 NR... more A colloidal route was exploited to synthesize TiO2 anisotropic nanocrystal rods in shape (TiO2 NRs) with a surface chemistry suited for their dispersibility and processability in apolar organic solvents. TiO2 NRs were dispersed in chloroform and n-heptane, respectively, and the two resulting formulations were investigated to identify the optimal conditions to achieve high-quality TiO2 NR-based coatings by the spray-coating application. In particular, the two types of TiO2 NR dispersions were first sprayed on silicon chips as a model substrate in order to preliminarily investigate the effect of the solvent and of the spraying time on the morphology and uniformity of the resulting coatings. The results of the SEM and AFM characterizations of the obtained coatings indicated n-heptane as the most suited solvent for TiO2 NR dispersion. Therefore, an n-heptane dispersion of TiO2 NRs was sprayed on a highly porous limestone—Lecce stone—very commonly used as building material in historic co...
Over the last few years, photocatalytic titanium dioxide coatings have been explored in laborator... more Over the last few years, photocatalytic titanium dioxide coatings have been explored in laboratory conditions to create building materials with self-cleaning and depolluting abilities. Assessing the performances of the photocatalytic surfaces under real conditions may provide basic knowledge to evaluate the potential of real applications of TiO 2 coatings in buildings. In this study, the performance of photocatalytic limestone surfaces obtained through coating with waterdispersed TiO 2 nanoparticles were investigated in an urban environment. Coated and uncoated samples were exposed to an urban site for one year. Before the exposure and periodically afterwards, optical microscopy observations, colour and contact angle measurements were performed on the sample surface. At the end of the exposure period, samples underwent a capillary water absorption test and self-cleaning efficiency was evaluated by a Rhodamine B photodegradation test. Ti and soluble fraction amounts on the sample surfaces were determined by X-ray Fluorescence (XRF) and ion chromatography, respectively. The overall results showed the TiO 2 coating was better able to preserve the surface colour properties early after exposure. After eight months, this effect was lost and the self-cleaning efficiency was reduced to negligible final rates. No clear wettability results and no meaningful capillary behaviour were recorded. A decrease of the photocatalytic activity was due to both partial titania loss and deactivation phenomena. The role of soluble salt ions either adsorbed from the environment or produced by the photocatalytic abatement of pollutants was recognized in the deactivation of the photocatalysts and their accumulation deserves attention for possible stone damage risk implications.
Field study of hydrophobic and selfcleaning TiO 2 NPs/fluoropolymer stone coatings • On the long ... more Field study of hydrophobic and selfcleaning TiO 2 NPs/fluoropolymer stone coatings • On the long run TiO 2 NPs did not interfere with the hydrophobicity of the polymer. • TiO 2-based coatings preserved cleaner surface than the mere fluoropolymer coating. • Photocatalytic efficiency reduced depending on the TiO 2 amounts in the mixtures. • TiO 2 embedded in the polymer limited salt ion loads absorbed by NPs on the surface.
h i g h l i g h t s UPV, Rebound and compressive microcore tests for stone masonry strength estim... more h i g h l i g h t s UPV, Rebound and compressive microcore tests for stone masonry strength estimation. Statistical evaluation of accuracy of each test measurements is performed. Multivariable methods improves correlation models between direct and indirect tests. Iterative cross-validation is effective in evaluating model predictive performances. Combined UPV and microcore strength tests gives the best estimation of UCS.
Rod-shaped TiO 2 nanocrystals (TiO 2 NRs), capped by oleic acid molecules (OLEA), were synthesize... more Rod-shaped TiO 2 nanocrystals (TiO 2 NRs), capped by oleic acid molecules (OLEA), were synthesized with controlled size, shape and surface chemistry by using colloidal routes. They were investigated for application as coating materials for preserving architectural stone of monumental and archaeological interest, in consideration of their self-cleaning and protection properties. For this purpose, two different deposition techniques, namely casting and dipping, were tested for the application of a nanocrystal dispersion on a defined stone type, as a relevant example of porous calcarenites, namely the Pietra Leccese, a building stone widely used in monuments and buildings of cultural and historic interest of the Apulia region (Italy). The physical properties of the stone surface were investigated before and after the treatment with the prepared nanostructured materials. In particular, colour, wettability, water transfer properties and stability of the coating were monitored as a function of time and of the application method. The self-cleaning properties of the TiO 2 NRs coated surfaces were tested under simulated and real solar irradiation. The obtained results were discussed in the light of the specific surface chemistry and morphology of TiO 2 NRs, demonstrating the effectiveness of TiO 2 NRs as an active component in formulations for stone protection.
Coating with nanostructured Titanium dioxide is able to enhance natural stone surface with self-c... more Coating with nanostructured Titanium dioxide is able to enhance natural stone surface with self-cleaning and depolluting abilities; nonetheless, the durability of the coatings is a crucial issue to be assessed in relation to their potential for use in the context of the building heritage. In this paper, the resistance of coatings applied on a compact and a soft limestone, which differ in roughness, porosity and cohesion features, has been investigated. A peeling and a water impact test were performed and their effect on the coated surface was evaluated as film loss by qualitative/quantitative ESEM-EDS analyses. Self-cleaning effectiveness was assessed by performing a photodegradation test of Rhodamine B. Crack-free and conformable films showed a good anchorage to both limestones; after the durability tests the coated surfaces exhibited almost unchanged Ti/Ca ratios and self-cleaning efficiencies. Large adhesion failures and decreased Ti amounts were recorded where coatings were fissured; they especially occurred on the surface of the compact limestone, along with a reduced self-cleaning ability. High surface roughness accounted for a better adhesion of both crack-free and fissured films to the soft limestone, but some erosion of the coated surface, which affected this friable stone under the water impact, compromised their preservation. Nonetheless, good self-cleaning performances were still provided due to the retention of nanoparticles under the surface. The overall results support that preservation of nanostructured TiO 2 coatings on the stone surface depends on the inherent characteristics of both films and supports; durability of the stone itself can play an important role.
Abstract In this work Ultrasonic Pulse Velocity (UPV), Schmidt Hammer Rebound (SHR) test and stre... more Abstract In this work Ultrasonic Pulse Velocity (UPV), Schmidt Hammer Rebound (SHR) test and strength assessment on microcores (UCS m ) and standard cubic samples (UCS c ) were used to detect the uniaxial compressive strength of stone masonry units. The analysis of the variability of the measurements allowed to investigate the significance of each test to differentiate the masonry blocks. The latter was evaluated by a Variability Index (VI), as the ratio between the variances at block scale and among the blocks. VI was found higher for UCS c and UPV than for UCS m and SHR measurements. A regression analysis aimed to the correlation of uniaxial compressive strengths evaluated by conventional destructive test on stone cubes with the other test results. The findings showed a good linear correlation among UCS c and UPV values (R 2 = 0.83), thus supporting the reliability of UPV to screen the masonry units and to estimate their uniaxial compressive strength. The correlation of UCS c with UCS m was reasonable (R 2 = 0.76), while it was low with SHR results; some limits related to the use of SHR and UCS m tests are also discussed.
Bulletin of Engineering Geology and the Environment, 2015
Many building materials have been functionalized to achieve photocatalytic properties, namely sel... more Many building materials have been functionalized to achieve photocatalytic properties, namely self-cleaning and depolluting abilities, through the application of photocatalytic TiO2 nanoparticles to those materials. These nanoparticles are able to preserve building façades by blocking the deposition of airborne particulates in polluted urban environments, and they are able to purify the air, thus benefiting the environment. In this study, the application of nanostructured TiO2 as a photoactive coating on two types of natural stone was investigated. A TiO2 sol obtained by sol–gel synthesis followed by hydrothermal processing was applied via spray deposition onto a compact limestone and a highly porous calcarenite. The effects of this coating on some basic properties of the stone, such as its color and water absorption, and the photocatalytic effectiveness of the coated surface were then studied. Scanning electron microscopy and energy-dispersive X-ray spectroscopy showed that the coating presented a uniform morphology on both types of stone, with the TiO2 nanoparticles penetrating <1 µm into the stone. The coating was found to be compatible with the properties of the investigated types of stone. Colorimetry indicated that the change in the color of the stone due to the coating was negligible. Measurements of the static contact angle and the results of the capillary water absorption test showed that photoinduced superhydrophilicity did not increase the amount of the water absorbed by the coated stone. A photodegradation test of rhodamine B demonstrated the self-cleaning ability of the coating on both types of stone. Conversely, the photocatalytic effectiveness of the coating—as measured by a nitrogen oxide abatement test—was found to be higher for the porous calcarenite than for the compact limestone, and to depend on the porosity and roughness of the substrate.
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Papers by Angela Calia