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Porous ceramics based on clay powders have been fabricated resulting in an open-cells structure. High porosity, measured between 46 and 96%, has been correlated with effective Young's modulus obtained by mechanical tests. However, it is worth noting that pore fraction is not the only physical feature which has to be taken into account to understand the elastic behaviour. SEM inspections show morphologies composed by ligaments and mass agglomerations which can influence mechanical response of these structures. In this sense, a statistical estimation of characteristics lengths of structural elements has been performed in order to calculate Young's modulus by using a modified tetrakaidecahedral phenomenological model. Moreover, the proposed approach is capable of taking into account shear effect owing to ligaments thickness usually ignored by beam theory. A comparison between experimental and computed data is in good agreement.

In this work, combined experimental and fractal nature analysis procedures are proposed in order to both model and design mechanical properties of porous ceramics. Several porous ceramics samples have been considered both from an in-situ experimental campaign and from the literature. Microstructural information concerning pore size distribution has been approximated by the Intermingled Fractal units (IFU) approach and effective mechanical properties are derived by a simple discrete model. The capability of the proposed methodology to reproduce high-scattered mechanical properties is fully shown and a comparison with classical bounds and estimates is also reported. Finally, the combined experimental, fractal nature analysis and homogenisation scheme is implemented as a design procedure for the technological production of advanced porous ceramics.

Porous clay ceramics represent an important class of construction materials. Their properties are strongly conditioned by microstructure features. In particular, a special attention has to be paid to porosity (pore fraction, pore shape, pore size, pore size distribution and topology distribution). In this work, thermal behaviour of porous ceramics has been studied comparing different modelling procedure. Fractal modelling, proposed in this paper, proves to be most reliable in predicting thermal behaviour of porous ceramics. For this reason, a design procedure for obtaining porous structures with specific thermal properties has been illustrated.

Clay roofing tiles have been subjected to freezing-thawing cycles. Analyses performed on the ceramic material highlight changes in the pore size distribution, and the consequent modification of the capillary suction behaviour. A model using intermingled fractal units (IFU) to mimic the porous structure satisfactorily describes the observed porosity evolution. Additionally, it successfully predicts the sorptivity coefficient. The results obtained are in good agreement with the experimental ones. In order to verify the ability of the IFU model to predict sorptivity coefficient, a comparison has been shown with other two analytical procedures. It is possible to note that IFU model better fits experimental values than other models found in the literature.

In this work, a semi-analytical model for the determination of effective mechanical properties of porous ceramic tiles obtained by pore forming agent is proposed. MIP tests allow measuring porosity and pore size distribution of experimental systems. These data are used for developing an Intermingled Fractal Units’ model (IFU) as approximant of porous microstructures. IFU model is then combined with classical structural mechanics theory for the analytical computation of the bending strength of brittle ceramic beams. Bounds and estimates are given in full form and the detailed algorithm can be easily implemented in a numerical package. A preliminary comparison with experimental data shows the capability of the proposed model to reproduce the effective mechanical behaviour of ceramic tiles.

An intermingled fractal units’ model is shown in order to simulate pore microstructures as pore fraction and pore size distribution. This model is aimed at predicting capillary water absorption coefficient and sorptivity values in cement pastes. The results obtained are in good agreement with the experimental ones. For validating this model, a comparison with other procedures has been shown. It is possible to establish that the newly proposed method matches better with the experimental results. That is probably due to the fact that pore size distribution has been considered as a whole. Moreover, even though the proposed model is based on fractal base units, it is able to simulate and predict different properties as well as nonfractal porous microstructure.

Advanced porous ceramics are a remarkable class of materials with important applications in engineering fields. Porosity features have received wide attention for their capability to influence all properties. In this paper, the correlation between pore structure and heat transfer has been studied. Different analytical procedures found in literature as well as an Intermingled Fractal Units’ model are proposed. Models predictions are compared with experimental data. It has been observed that IFU is particularly suitable to predict thermal conductivity values very close to experimental ones. This fact is related to its capability to replicate porous microstructures in terms of pore volume fraction, pore size range and pore size distribution.

Water vapour flux into the porous microstructure represents a crucial factor capable of influencing the degradation of porous materials. This fact is of utmost importance especially considering materials installed in cultural heritage. The necessity to preserve stone artworks pushes to perform surface protective coatings that create an intermediate sacrificial layer between stone and the environment. High hydrophobicity and high permeability of water vapour must be one of the most important requirements of a protective film. These features depend upon the nature of coatings as well as the porous microstructures. In order to control coatings’ effects and their influence on final water vapour permeability ( δ ) properties, a new modelling procedure has been proposed. The study is conducted on a porous limestone, namely Pietra Leccese, which is being largely used for historical constructions in Mediterranean. The average experimental water vapour permeability δ exp is 4.83 × 10 −4 and 3.86 × 10 −4 (g/m d Pa) respectively for untreated and treated PL stone, while the average model prediction δ IFU is 4.87 × 10 −4 and 3.77 × 10 −4 (g/m d Pa) respectively for untreated and treated PL stone. The good agreement between experimental and calculated data shows that the proposed modelling procedure could represent a good tool for designing and controlling protection activity on cultural heritage.

This study presents an intermingled fractal model (IFU) capable of simulating the porous microstructure of natural calcareous stone substrate, typical of Apulia Region (Pietra Leccese, PL) used in historical buildings. The developed model is aimed at predicting, by an analytical approach, the thermal conductivity of these materials. To verify the actual ability of the proposed method to predict stone thermal conductivity, the intermingled fractal units model was applied to untreated natural stone, and to the same stone, treated with a novel UV-light curable O–I hybrid coating. The application of hydrophobic polymers to stone materials is, in fact, an effective way to preserve stone artifacts and protect cultural heritage from decay. To this aim, a novel experimental photopolymerizable organic–inorganic (O–I) hybrid protective coating, mainly intended for the protection of PL stone, was previously developed by some of the authors. The innovative hybrid product evidenced an extraordinary hydrophobicity, able to guarantee a very high preservation of the stone from water actions, as well as another important property required to a protective, i.e., a high traspirability of the stone substrate. Furthermore, the experimental product proposed was able to equal the performance of commercial available products, with the adjunctive advantage to be free-solvent.

Porous yittria-stabilized zirconia is an important advanced ceramic material for technological applications. One of the most important characteristics of this material is low thermal conductivity, which is greatly influenced by the presence of pores into the microstructure. In fact, air trapped in the pores represents a better thermal insulator. The role of the pore volume fraction on porous material characteristics has been extensively studied. On the other hand, the influence of the structure disorder, the pore size range and pore size distribution have been studied much less. In this study, an intermingled fractal model capable of relating thermal properties of ceramic materials and their pore microstructure has been proposed. Model predictions are found confirming the experimental data fairly well, even better than the others models available in the literature.

Thermal conductivity is one of the most important parameters for construction and building materials. Indeed, extensive efforts have been put in by Europe in order to decrease energy consumption at various levels. However, with regards to historical buildings, the measures of thermal performance are not simple and they, in fact, pose a wide range of error. In this paper, an intermingled fractal model has been proposed, which is capable of reproducing the porous microstructure. Moreover, by converting this model into an electrical circuit, it is capable of predicting thermal conductivity. The results are in perfect agreement with experimental ones obtained by climatic chamber.

This work proposes the application of a new simulation method based on fractal geometry for the calculation of the thermal conductivity for building materials. The results obtained are compared with the measurement, in a climatic chamber, of the heat flow through a material chosen as the sample. The test sample is made with “pietracantone”, a stone widely used as a building material and as an ornamental stone in the areas of Cagliari and Sassari in Sardinia. This material is characterized by a limestone matrix and a porosity which significantly influences the value of thermal conductivity. It is not known to the authors that this material had already been studied for its thermal properties.

The influence of the pore size distribution on the elastic modulus has been studied using an intermingled fractal model (IFU) capable to reproduce entirely pore size distribution of materials. The results obtained from IFU modelling are in good agreement with experimental ones. The model could be considered as a microstructure simulator to improve mechanical properties of porous ceramic materials.

This work focuses on the relationship between water vapour permeability and porosity in earthen materials. Earth blocks have been suitably fabricated and their pore size distribution evaluated along with water vapour permeability. Experimental results are compared with theoretical predictions obtained from a fractal model relating porosity to transport processes. Experimental and modelling outcomes compare remarkably well, thus making the fractal model show promise for addressing the design of earth materials with tailored properties.

The paper represents the “state of the art” on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.

This review presents “a state of the art” report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1—the present paper—focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Porous ceramic materials can be produced by different techniques. One of the most important is pore agent method. The pore fraction, size, shape and distribution are linked to the pore-forming agent. In these materials porosity has a great influence in their physical properties and one of them is thermal conductivity. The role of the pore size distribution has been studied much less than pore fraction, probably because it is very difficult to describe and to characterize it. For this reason, in this paper, an original intermingled fractal model to predict thermal conductivity (taking into account entirely pore size distribution) has been proposed. This model is capable to reproduce fractal or non-fractal microstructure. Calculated data are in good agreement with experimental ones. The model could be considered as a microstructure simulator to improve thermal performance of porous ceramic materials.

Water sorptivity symbolises an important property associated with the preservation of porous construction materials. The water movement into the microstructure is responsible for deterioration of different types of materials and consequently for the indoor comfort worsening. In this context, experimental sorptivity tests are incompatible, because they require large quantities of materials in order to statistically validate the results. Owing to these reasons, the development of analytical procedure for indirect sorptivity valuation from MIP data would be highly beneficial. In this work, an Intermingled Fractal Units’ model has been proposed to evaluate sorptivity coefficient of calcareous stones, mostly used in historical buildings of Cagliari, Sardinia. The results are compared with experimental data as well as with other two models found in the literature. IFU model better fits experimental data than the other two models, and it represents an important tool for estimating service life of porous building materials.

The Sorptivity is a coefficient very important to characterize porous materials. It is associated to principal properties such as mechanical durability, thermal and electrical conductivity, etc. In this work, the Sorptivity coefficient of several systems of porous ceramics has been measured following the experimental procedure. In different situations, this very simple test could be not performed; in cultural heritage or during an optimised industrial process. Major reasons for this inability include that it would demand great quantitates of materials impossible to withdraw from the protected building, as well as the experimental test can last for several days, which reduces the possibility to correct/improve the industrial production process. In this regards, being very useful to have analytical formulas in order to calculate Sorptivity coefficient, an Intermingled Fractal Units model has been proposed. Starting from its capability to reproduce entirely the pore size distributions of porous materials, IFU is used to simulate water absorption process and to estimate the Sorptivity coefficient. The obtained results are in good agreement with experimental data and others two models predictions. This fact allows considering IFU model as a future tool for design materials and to predict their service life.