This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and w... more 3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and without metakaolin to produce sustainable multifunctional diatomite-based geopolymeric foams. Suitable amount of Silicon powder and vegetable surfactant were used as foaming agents, while polysilicate solution was used as reactive crosslinker. The resulting porous materials, characterized by hierarchical porosity ranging from macro to nano-scale, were fabricated at 40°C for 24 h and characterized by means of chemical and morphological investigations, contact angle, thermal and acoustic properties and fire reaction. The presence of diatomite in the produced foams provides an increase of thermal inertia, and the thermal insulation performance firstly due to the intrinsically low thermal conductivity of diatomite and also because silicon and vegetable surfactant are able to promote the formation of a cocontinuous mesoporous structure. Furthermore, the created morphological structure provides a good acoustic absorption coefficient in a wide range of frequency. Finally, due to their hydrophilicity/oleophobicity character, diatomite-based geopolymeric foams could, potentially, be proposed as oil/water separation membranes.
The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and... more The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and Al initially dissolved is essential for the following polycondensation and can strongly influence physical and mechanical performances of the final product. In order to set up a method to test the ability of a material to react in alkaline media, different aluminosilicate sources have been selected: a mineral resource (a zeolitized tuff), an industrial by product (silt from washing process of construction and demolition wastes), a heat treated clay sediment and a calcined clay (metakaolin). Two test methods, static and dynamic, have been applied to evaluate the attitude of a silicoaluminate precursor to give a geopolymerization reaction. In particular, a fixed amount of precursor was put into contact with a alkaline solution under continuous stirring or in static conditions at 60 • C for fixed times. The dynamic test method seems to be more suitable, since it is faster and requires lower amounts of reactants (solution). Moreover, the dynamic test provides a reactivity sequence (ordered from the more to the less reactive precursor) metakaolin > treated clay sediment > zeolitized tuff ≈ silt both for Si and Al release, which is coherent with the performances of geopolymers obtained by using the above precursors.
Demolition activity plays an important role in the total energy consumption of the construction i... more Demolition activity plays an important role in the total energy consumption of the construction industry in the European Union. The indiscriminate use of non-renewable raw materials, energy consumption, and unsustainable design has led to a redefinition of the criteria to ensure environmental protection. This article introduces an experimental plan that determines the viability of a new type of construction material, obtained from crushed brick waste, to be introduced into the construction market. The potential of crushed brick waste as a raw material in the production of building precast products, obtained by curing a geopolymeric blend at 60 °C for 3 days, has been exploited. Geopolymers represent an important alternative in reducing emissions and energy consumption, whilst, at the same time, achieving a considerable mechanical performance. The results obtained from this study show that the geopolymers produced from crushed brick were characterized by good properties in terms of o...
Alkali activated ceramic foams have been produced by using metakaolin and/or diatomite as alumino... more Alkali activated ceramic foams have been produced by using metakaolin and/or diatomite as aluminosilicate source, an aqueous sodium silicate solution as alkali activator and Na2SiF6 as a catalyst that promotes the gelification of the entire system. Two different techniques of direct foaming have been coupled, one based on chemical reactions with gas production and the other one based on a mechanical foaming. Then, other levels of hierarchical porosity (nanometric and macrometric scale) have been added to the produced expanded ceramic systems. This approach allows to tailor the chemical–physical properties and density of the resulted hybrid foams. The produced foams have been mechanically, chemically, physically and morphologically characterized. Moreover, their acoustic and thermal properties, in terms of thermal stability and conductivity, and also their fire behavior have been investigated.
This research explores the new perspectives in conservation and protection of two macroporous tuf... more This research explores the new perspectives in conservation and protection of two macroporous tuff stones, widely employed in the architectural heritage of Campania region, characterized by highly heterogeneous rock fabric and texture and a variable mineralogical composition that represent crucial factors responsible for their weak durability. The consolidation treatments were performed with a recently and widely used suspension of nano-silica crystals in water and with a lithium silicate solution that has received up to now scarce attention as a consolidant agent. Physical investigations (open porosity, Hg porosimetry, water absorption), morphological observations (SEM analyses) and visual appearance test (colorimetric measurements), along with assessments of performance indicators such as ultrasonic pulse velocity, surface cohesion test (peeling test) and durability test (salt crystallization), were carried out to investigate the consolidation effectiveness. Overall, lithium silic...
Additive Manufacturing (AM) is a technological process in which elements are fruitfully built up ... more Additive Manufacturing (AM) is a technological process in which elements are fruitfully built up adding materials layer by layer. AM had a massive development in recent times, thanks to its intrinsic advantages, especially if compared with conventional processes (i.e. subtractive manufacturing methods), in terms of free-form design, high customization of products, a significant reduction in raw materials consumption, low request of postprocessing and heat treatments, use of pure materials and reduced time for final products to be marketed. In order to give an innovative contribution to the knowledge in the field of metal AM materials, this paper reports the main outcomes of an experimental campaign focused on the influence of several specific printing parameters on the mechanical features of the 17-4PH stainless steel, which is one of the most used metal for the Selective Laser Melting (SLM) technology. The influence of different printing directions and sample inclinations on the ma...
Abstract Gypsum plasterboards are nowadays very appreciated in buildings, mainly due to their lig... more Abstract Gypsum plasterboards are nowadays very appreciated in buildings, mainly due to their lightness, thermal insulation and suitable sound transmission loss when used in double walls. However thermal and acoustic features of gypsum plasterboard can be enhanced. In the present study an innovative method, consisting in the direct addition of a pre-manufactured foam to gypsum pastes is used to increase the gypsum porosity improving sound absorption, lightness and thermal insulation features. In this aim, the role of both different amounts and dilutions of a vegetal foaming agent on the main physical, mechanical and microstructural characteristics of the gypsum was experimentally investigated. Moreover, also X-ray computed micro tomography technique (Micro-CT) was carried out in order to investigate the 3D internal microstructure of the materials. The results confirmed the effectiveness of the foaming agent in increasing the gypsum porosity, with a linear correlation between densities and mechanical strengths. Moreover, the presence of large bubbles, mainly connected each other, involved in a strong reduction of the thermal coefficient (λ), from 0.57 W/m∙K of REF sample to 0.25 W/m∙K of LG10_5% sample, and in a strong increase of the normal sound absorption coefficient (α0), from 0.06 of REF sample to 0.20 of LG10_5% sample. Finally, in the light of the results obtained by the present research, the use of a pre-whipped vegetal foaming agent represents a suitable way to obtain lightweight gypsum-based materials with enhanced thermal and acoustic properties.
The design of the production process of diatomite-based ceramic foams, starting from different pe... more The design of the production process of diatomite-based ceramic foams, starting from different percentages of metakaolin, diatomite, and sodium silicate solution as reactive ingredients and vegetable surfactant and silicon powder as blowing agents, has been set up. The foams were obtained using the double effect of different foaming approaches: mechanical stirring and chemical foaming. Six systems were prepared fixing the amount of diatomite (100%) and adding in the starting mixture of different percentages (0.05, 0.1, 0.25, 0.5, 0.75, and 1 wt%) of silicon metal. Once the optimal percentage of silicon metal (0.05%) is chosen thanks to XRD analysis, other three systems were prepared only changing the amount of diatomite (50, 70, and 100 wt%) in starting formulation. The foam obtained with 100% of diatomite results to be the optimized final formulation, as it shows a hierarchical porosity with a high homogeneity of the matrix at the same time. The results highlighted that the best performances in terms of lightness, high porosity as well as homogenous microstructure were obtained using, with respect to the total amount, 6 wt% of mechanical stirred vegetable surfactant together with 0.05 wt% of Si as physical and chemical blowing agents, respectively.
Abstract The management of huge amounts of waste deriving from several anthropogenic activities, ... more Abstract The management of huge amounts of waste deriving from several anthropogenic activities, such as manufacturing, construction, mining and quarrying, dredging, represents a great contemporary environmental challenge for many countries worldwide. Among the different recycling possibilities, the use of the excavated soils, obtained from operations such as tunneling, excavations, mining, dredging etc., which are generally considered as soil waste, in the production of innovative eco-sustainable building materials represents an interesting alternative to their disposal. In fact, considering especially their chemical composition, low cost and easy availability, soil wastes seem to be the ideal candidates to be used as secondary raw materials for the manufacture of geopolymer-based materials. The paper intends to present a review of the recent scientific literature regarding the use of different types of soil waste to produce geopolymeric binders. Particular attention is focused on mining waste (deriving from various types of mining industries) and dredged sediments coming from marine harbors and natural and artificial water reservoirs, in order to understand and critically discuss the limits of their disposal approach and, at the same time, show perspectives and challenges for possible future research activities in this field. The production of geopolymer-based building components, starting from mining waste and reservoir sediments, is widely discussed thanks to the numerous scientific findings, while the recycling of marine dredged sediments through geopolymerization represents a completely new and innovative trend in research activity, in fact only few related papers were found in literature. It can be strongly stated that geopolymerization can significantly contribute to a sustainable improvement of soil waste management systems.
The paper deals with the production of lightweight gypsum composites by means of a vegetal protei... more The paper deals with the production of lightweight gypsum composites by means of a vegetal protein foaming agent. Two manufacturing methods, which basically differ in the physical state of the foaming agent used, have been proposed and the relative experimental results have been compared and discussed. The gypsum foam samples have been characterized from several points of view (physical, mechanical and microstructural). Thermal and acoustic properties and also porosity have been investigated in order to evaluate the insulation features of the lightweight gypsum composites. The addition of foaming agent strongly affected the mechanical performance of all the samples and led to a significant modification of the post-cracking behavior. Differences observed in the morphology and porosity, related to the two manufacturing methods, are due to the method of pore-formation, especially to the different amounts of air insufflated within the gypsum pastes which influence, in addition to the porosity, the final microstructure and consequently the insulation performances of the gypsum foams. In fact, the more porous samples, obtained from the addition of the liquid foaming agent, showed both the lower values of thermal conductivity and the better values of sound absorption coefficient, leading to a final lightweight products characterized by improved insulation properties.
Motivated by the hierarchical micro and nanoscale features in terms of porosity of diatomite, the... more Motivated by the hierarchical micro and nanoscale features in terms of porosity of diatomite, the production of ceramic-graded porous foams with tailored porosity, obtained by using it as raw material, has been proposed. The main challenge during the foam-production process has been the preservation of diatomite nanometric porosity and the addition of other levels of hierarchical porosity. The coupled use of two techniques of direct foaming (chemical and mechanical), combined with the use of 3D printing inverse replica method, assured the achievement of porosity of, respectively, microscopic and macroscopic dimensions. Optical and scanning electron microscopies have been performed for an in-depth characterization of the final microstructure. XRD analysis has been carried out to check the influence of sacrificial templates on the matrix mineralogical composition. The porosity of the diatomite-based foams has been investigated by means of nitrogen-adsorption analysis and mercury-intru...
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and w... more 3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and without metakaolin to produce sustainable multifunctional diatomite-based geopolymeric foams. Suitable amount of Silicon powder and vegetable surfactant were used as foaming agents, while polysilicate solution was used as reactive crosslinker. The resulting porous materials, characterized by hierarchical porosity ranging from macro to nano-scale, were fabricated at 40°C for 24 h and characterized by means of chemical and morphological investigations, contact angle, thermal and acoustic properties and fire reaction. The presence of diatomite in the produced foams provides an increase of thermal inertia, and the thermal insulation performance firstly due to the intrinsically low thermal conductivity of diatomite and also because silicon and vegetable surfactant are able to promote the formation of a cocontinuous mesoporous structure. Furthermore, the created morphological structure provides a good acoustic absorption coefficient in a wide range of frequency. Finally, due to their hydrophilicity/oleophobicity character, diatomite-based geopolymeric foams could, potentially, be proposed as oil/water separation membranes.
The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and... more The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and Al initially dissolved is essential for the following polycondensation and can strongly influence physical and mechanical performances of the final product. In order to set up a method to test the ability of a material to react in alkaline media, different aluminosilicate sources have been selected: a mineral resource (a zeolitized tuff), an industrial by product (silt from washing process of construction and demolition wastes), a heat treated clay sediment and a calcined clay (metakaolin). Two test methods, static and dynamic, have been applied to evaluate the attitude of a silicoaluminate precursor to give a geopolymerization reaction. In particular, a fixed amount of precursor was put into contact with a alkaline solution under continuous stirring or in static conditions at 60 • C for fixed times. The dynamic test method seems to be more suitable, since it is faster and requires lower amounts of reactants (solution). Moreover, the dynamic test provides a reactivity sequence (ordered from the more to the less reactive precursor) metakaolin > treated clay sediment > zeolitized tuff ≈ silt both for Si and Al release, which is coherent with the performances of geopolymers obtained by using the above precursors.
In this paper fly ash based geopolymer mortars have been prepared and their thermal behavior eval... more In this paper fly ash based geopolymer mortars have been prepared and their thermal behavior evaluated in order to assess the suitability of fly ash based alkali-activated binders for thermal energy storage in solar thermal plants. Different parameters, such as binder/aggregate ratio, percentage of fly ash replaced by slag, temperature and curing time, have been changed and optimized using the Design Of Experiments (DOE) approach. In order to estimate the thermal cycling stability of geopolymeric mortars at elevated temperatures, mechanical strength and weight loss of each sample subjected to different thermal cycles in the temperature range 150e550 C were evaluated. Finally, thermal conductivity of some of the mixtures, selected on basis of the thermal stability test results, have been measured. Fly ash based geopolymeric mortars remained stable after each thermal treatment and specimens treated at elevated temperatures retained acceptable compressive strength. The thermal stability was preserved also after repeated thermal cycles, proving that fly ash based geopolymers are suitable materials for thermal energy storage concretes.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and w... more 3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and without metakaolin to produce sustainable multifunctional diatomite-based geopolymeric foams. Suitable amount of Silicon powder and vegetable surfactant were used as foaming agents, while polysilicate solution was used as reactive crosslinker. The resulting porous materials, characterized by hierarchical porosity ranging from macro to nano-scale, were fabricated at 40°C for 24 h and characterized by means of chemical and morphological investigations, contact angle, thermal and acoustic properties and fire reaction. The presence of diatomite in the produced foams provides an increase of thermal inertia, and the thermal insulation performance firstly due to the intrinsically low thermal conductivity of diatomite and also because silicon and vegetable surfactant are able to promote the formation of a cocontinuous mesoporous structure. Furthermore, the created morphological structure provides a good acoustic absorption coefficient in a wide range of frequency. Finally, due to their hydrophilicity/oleophobicity character, diatomite-based geopolymeric foams could, potentially, be proposed as oil/water separation membranes.
The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and... more The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and Al initially dissolved is essential for the following polycondensation and can strongly influence physical and mechanical performances of the final product. In order to set up a method to test the ability of a material to react in alkaline media, different aluminosilicate sources have been selected: a mineral resource (a zeolitized tuff), an industrial by product (silt from washing process of construction and demolition wastes), a heat treated clay sediment and a calcined clay (metakaolin). Two test methods, static and dynamic, have been applied to evaluate the attitude of a silicoaluminate precursor to give a geopolymerization reaction. In particular, a fixed amount of precursor was put into contact with a alkaline solution under continuous stirring or in static conditions at 60 • C for fixed times. The dynamic test method seems to be more suitable, since it is faster and requires lower amounts of reactants (solution). Moreover, the dynamic test provides a reactivity sequence (ordered from the more to the less reactive precursor) metakaolin > treated clay sediment > zeolitized tuff ≈ silt both for Si and Al release, which is coherent with the performances of geopolymers obtained by using the above precursors.
Demolition activity plays an important role in the total energy consumption of the construction i... more Demolition activity plays an important role in the total energy consumption of the construction industry in the European Union. The indiscriminate use of non-renewable raw materials, energy consumption, and unsustainable design has led to a redefinition of the criteria to ensure environmental protection. This article introduces an experimental plan that determines the viability of a new type of construction material, obtained from crushed brick waste, to be introduced into the construction market. The potential of crushed brick waste as a raw material in the production of building precast products, obtained by curing a geopolymeric blend at 60 °C for 3 days, has been exploited. Geopolymers represent an important alternative in reducing emissions and energy consumption, whilst, at the same time, achieving a considerable mechanical performance. The results obtained from this study show that the geopolymers produced from crushed brick were characterized by good properties in terms of o...
Alkali activated ceramic foams have been produced by using metakaolin and/or diatomite as alumino... more Alkali activated ceramic foams have been produced by using metakaolin and/or diatomite as aluminosilicate source, an aqueous sodium silicate solution as alkali activator and Na2SiF6 as a catalyst that promotes the gelification of the entire system. Two different techniques of direct foaming have been coupled, one based on chemical reactions with gas production and the other one based on a mechanical foaming. Then, other levels of hierarchical porosity (nanometric and macrometric scale) have been added to the produced expanded ceramic systems. This approach allows to tailor the chemical–physical properties and density of the resulted hybrid foams. The produced foams have been mechanically, chemically, physically and morphologically characterized. Moreover, their acoustic and thermal properties, in terms of thermal stability and conductivity, and also their fire behavior have been investigated.
This research explores the new perspectives in conservation and protection of two macroporous tuf... more This research explores the new perspectives in conservation and protection of two macroporous tuff stones, widely employed in the architectural heritage of Campania region, characterized by highly heterogeneous rock fabric and texture and a variable mineralogical composition that represent crucial factors responsible for their weak durability. The consolidation treatments were performed with a recently and widely used suspension of nano-silica crystals in water and with a lithium silicate solution that has received up to now scarce attention as a consolidant agent. Physical investigations (open porosity, Hg porosimetry, water absorption), morphological observations (SEM analyses) and visual appearance test (colorimetric measurements), along with assessments of performance indicators such as ultrasonic pulse velocity, surface cohesion test (peeling test) and durability test (salt crystallization), were carried out to investigate the consolidation effectiveness. Overall, lithium silic...
Additive Manufacturing (AM) is a technological process in which elements are fruitfully built up ... more Additive Manufacturing (AM) is a technological process in which elements are fruitfully built up adding materials layer by layer. AM had a massive development in recent times, thanks to its intrinsic advantages, especially if compared with conventional processes (i.e. subtractive manufacturing methods), in terms of free-form design, high customization of products, a significant reduction in raw materials consumption, low request of postprocessing and heat treatments, use of pure materials and reduced time for final products to be marketed. In order to give an innovative contribution to the knowledge in the field of metal AM materials, this paper reports the main outcomes of an experimental campaign focused on the influence of several specific printing parameters on the mechanical features of the 17-4PH stainless steel, which is one of the most used metal for the Selective Laser Melting (SLM) technology. The influence of different printing directions and sample inclinations on the ma...
Abstract Gypsum plasterboards are nowadays very appreciated in buildings, mainly due to their lig... more Abstract Gypsum plasterboards are nowadays very appreciated in buildings, mainly due to their lightness, thermal insulation and suitable sound transmission loss when used in double walls. However thermal and acoustic features of gypsum plasterboard can be enhanced. In the present study an innovative method, consisting in the direct addition of a pre-manufactured foam to gypsum pastes is used to increase the gypsum porosity improving sound absorption, lightness and thermal insulation features. In this aim, the role of both different amounts and dilutions of a vegetal foaming agent on the main physical, mechanical and microstructural characteristics of the gypsum was experimentally investigated. Moreover, also X-ray computed micro tomography technique (Micro-CT) was carried out in order to investigate the 3D internal microstructure of the materials. The results confirmed the effectiveness of the foaming agent in increasing the gypsum porosity, with a linear correlation between densities and mechanical strengths. Moreover, the presence of large bubbles, mainly connected each other, involved in a strong reduction of the thermal coefficient (λ), from 0.57 W/m∙K of REF sample to 0.25 W/m∙K of LG10_5% sample, and in a strong increase of the normal sound absorption coefficient (α0), from 0.06 of REF sample to 0.20 of LG10_5% sample. Finally, in the light of the results obtained by the present research, the use of a pre-whipped vegetal foaming agent represents a suitable way to obtain lightweight gypsum-based materials with enhanced thermal and acoustic properties.
The design of the production process of diatomite-based ceramic foams, starting from different pe... more The design of the production process of diatomite-based ceramic foams, starting from different percentages of metakaolin, diatomite, and sodium silicate solution as reactive ingredients and vegetable surfactant and silicon powder as blowing agents, has been set up. The foams were obtained using the double effect of different foaming approaches: mechanical stirring and chemical foaming. Six systems were prepared fixing the amount of diatomite (100%) and adding in the starting mixture of different percentages (0.05, 0.1, 0.25, 0.5, 0.75, and 1 wt%) of silicon metal. Once the optimal percentage of silicon metal (0.05%) is chosen thanks to XRD analysis, other three systems were prepared only changing the amount of diatomite (50, 70, and 100 wt%) in starting formulation. The foam obtained with 100% of diatomite results to be the optimized final formulation, as it shows a hierarchical porosity with a high homogeneity of the matrix at the same time. The results highlighted that the best performances in terms of lightness, high porosity as well as homogenous microstructure were obtained using, with respect to the total amount, 6 wt% of mechanical stirred vegetable surfactant together with 0.05 wt% of Si as physical and chemical blowing agents, respectively.
Abstract The management of huge amounts of waste deriving from several anthropogenic activities, ... more Abstract The management of huge amounts of waste deriving from several anthropogenic activities, such as manufacturing, construction, mining and quarrying, dredging, represents a great contemporary environmental challenge for many countries worldwide. Among the different recycling possibilities, the use of the excavated soils, obtained from operations such as tunneling, excavations, mining, dredging etc., which are generally considered as soil waste, in the production of innovative eco-sustainable building materials represents an interesting alternative to their disposal. In fact, considering especially their chemical composition, low cost and easy availability, soil wastes seem to be the ideal candidates to be used as secondary raw materials for the manufacture of geopolymer-based materials. The paper intends to present a review of the recent scientific literature regarding the use of different types of soil waste to produce geopolymeric binders. Particular attention is focused on mining waste (deriving from various types of mining industries) and dredged sediments coming from marine harbors and natural and artificial water reservoirs, in order to understand and critically discuss the limits of their disposal approach and, at the same time, show perspectives and challenges for possible future research activities in this field. The production of geopolymer-based building components, starting from mining waste and reservoir sediments, is widely discussed thanks to the numerous scientific findings, while the recycling of marine dredged sediments through geopolymerization represents a completely new and innovative trend in research activity, in fact only few related papers were found in literature. It can be strongly stated that geopolymerization can significantly contribute to a sustainable improvement of soil waste management systems.
The paper deals with the production of lightweight gypsum composites by means of a vegetal protei... more The paper deals with the production of lightweight gypsum composites by means of a vegetal protein foaming agent. Two manufacturing methods, which basically differ in the physical state of the foaming agent used, have been proposed and the relative experimental results have been compared and discussed. The gypsum foam samples have been characterized from several points of view (physical, mechanical and microstructural). Thermal and acoustic properties and also porosity have been investigated in order to evaluate the insulation features of the lightweight gypsum composites. The addition of foaming agent strongly affected the mechanical performance of all the samples and led to a significant modification of the post-cracking behavior. Differences observed in the morphology and porosity, related to the two manufacturing methods, are due to the method of pore-formation, especially to the different amounts of air insufflated within the gypsum pastes which influence, in addition to the porosity, the final microstructure and consequently the insulation performances of the gypsum foams. In fact, the more porous samples, obtained from the addition of the liquid foaming agent, showed both the lower values of thermal conductivity and the better values of sound absorption coefficient, leading to a final lightweight products characterized by improved insulation properties.
Motivated by the hierarchical micro and nanoscale features in terms of porosity of diatomite, the... more Motivated by the hierarchical micro and nanoscale features in terms of porosity of diatomite, the production of ceramic-graded porous foams with tailored porosity, obtained by using it as raw material, has been proposed. The main challenge during the foam-production process has been the preservation of diatomite nanometric porosity and the addition of other levels of hierarchical porosity. The coupled use of two techniques of direct foaming (chemical and mechanical), combined with the use of 3D printing inverse replica method, assured the achievement of porosity of, respectively, microscopic and macroscopic dimensions. Optical and scanning electron microscopies have been performed for an in-depth characterization of the final microstructure. XRD analysis has been carried out to check the influence of sacrificial templates on the matrix mineralogical composition. The porosity of the diatomite-based foams has been investigated by means of nitrogen-adsorption analysis and mercury-intru...
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and w... more 3D-structured silica exoskeletons-diatomite was used as reactive inorganic ingredient, with and without metakaolin to produce sustainable multifunctional diatomite-based geopolymeric foams. Suitable amount of Silicon powder and vegetable surfactant were used as foaming agents, while polysilicate solution was used as reactive crosslinker. The resulting porous materials, characterized by hierarchical porosity ranging from macro to nano-scale, were fabricated at 40°C for 24 h and characterized by means of chemical and morphological investigations, contact angle, thermal and acoustic properties and fire reaction. The presence of diatomite in the produced foams provides an increase of thermal inertia, and the thermal insulation performance firstly due to the intrinsically low thermal conductivity of diatomite and also because silicon and vegetable surfactant are able to promote the formation of a cocontinuous mesoporous structure. Furthermore, the created morphological structure provides a good acoustic absorption coefficient in a wide range of frequency. Finally, due to their hydrophilicity/oleophobicity character, diatomite-based geopolymeric foams could, potentially, be proposed as oil/water separation membranes.
The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and... more The extent of the dissolution of aluminosilicate compounds is crucial, since the amount of Si and Al initially dissolved is essential for the following polycondensation and can strongly influence physical and mechanical performances of the final product. In order to set up a method to test the ability of a material to react in alkaline media, different aluminosilicate sources have been selected: a mineral resource (a zeolitized tuff), an industrial by product (silt from washing process of construction and demolition wastes), a heat treated clay sediment and a calcined clay (metakaolin). Two test methods, static and dynamic, have been applied to evaluate the attitude of a silicoaluminate precursor to give a geopolymerization reaction. In particular, a fixed amount of precursor was put into contact with a alkaline solution under continuous stirring or in static conditions at 60 • C for fixed times. The dynamic test method seems to be more suitable, since it is faster and requires lower amounts of reactants (solution). Moreover, the dynamic test provides a reactivity sequence (ordered from the more to the less reactive precursor) metakaolin > treated clay sediment > zeolitized tuff ≈ silt both for Si and Al release, which is coherent with the performances of geopolymers obtained by using the above precursors.
In this paper fly ash based geopolymer mortars have been prepared and their thermal behavior eval... more In this paper fly ash based geopolymer mortars have been prepared and their thermal behavior evaluated in order to assess the suitability of fly ash based alkali-activated binders for thermal energy storage in solar thermal plants. Different parameters, such as binder/aggregate ratio, percentage of fly ash replaced by slag, temperature and curing time, have been changed and optimized using the Design Of Experiments (DOE) approach. In order to estimate the thermal cycling stability of geopolymeric mortars at elevated temperatures, mechanical strength and weight loss of each sample subjected to different thermal cycles in the temperature range 150e550 C were evaluated. Finally, thermal conductivity of some of the mixtures, selected on basis of the thermal stability test results, have been measured. Fly ash based geopolymeric mortars remained stable after each thermal treatment and specimens treated at elevated temperatures retained acceptable compressive strength. The thermal stability was preserved also after repeated thermal cycles, proving that fly ash based geopolymers are suitable materials for thermal energy storage concretes.
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