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Biochar-containing cement composites have attracted increasing interest in recent years due to the possibility of reducing the environmental impact linked to cement. They can also improve the mechanical properties and the electrical conductivity of cement-based materials. One parameter that can affect the mechanical performance of biochar-containing cement composites is the morphology of the biochar. While it is reasonable to expect a different behaviour for different shapes (sheet-, sphere- or rod-shaped), a full understanding is yet to be achieved of the competing effects of aspect ratio, morphology and composition linked to the specific biochar source. This study shows that biochar can improve the mechanical properties of cement-based composites: 1 wt% of biochar improves compressive strength and flexural strength by 7% and 15%, respectively. The results presented in this study confirm that biochar has a positive effect on both the mechanical and environmental behaviour of cement-based materials.

Even if cement is a well-consolidated material, the chemistry of cement (and the chemistry inside cement) remains very complex and still non-obvious. What is sure is that the hydration mechanism plays a pivotal role in the development of cements with specific final chemical compositions, mechanical properties, and porosities. This document provides a survey of the chemistry behind such inorganic material. The text has been organized into five parts describing: (i) the manufacture process of Portland cement, (ii) the chemical composition and hydration reactions involving a Portland cement, (iii) the mechanisms of setting, (iv) the classification of the different types of porosities available in a cement, with particular attention given to the role of water in driving the formation of pores, and (v) the recent findings on the use of recycled waste materials in cementitious matrices, with a particular focus on the sustainable development of cementitious formulations. From this study, the influence of water on the main relevant chemical transformations occurring in cement clearly emerged, with the formation of specific intermediates/products that might affect the final chemical composition of cements. Within the text, a clear distinction between setting and hardening has been provided. The physical/structural role of water in influencing the porosities in cements has been analyzed, making a correlation between types of bound water and porosities. Lastly, some considerations on the recent trends in the sustainable reuse of waste materials to form “green” cementitious composites has been discussed and future considerations proposed.

Waste management is a most current topic, and as such, numerous articles in literature discuss over the recycling and re-use of waste materials from various fields. A common solution is the to use these materials as partial substituent of the inert fraction in concretes and mortars. This work focuses on the possibility of using Acanthocardia tuberculata seashells, which constitute a food waste destined to landfilling, as partial substituents of inert in mortars. The results obtained evidenced that the reduction in mechanical properties (in terms of toughness and flexural stress) is mainly due to the water absorption properties of seashells aggregates, which affect the hydration of the cement. However, as experimentally demonstrated, such decrease in mechanical properties in any case does not compromise the performance of the material when used for civil applications. Resumen: La gestión de residuos es un tema actual, y como tal, numerosos artículos en la literatura discuten sobre el reciclaje y la reutilización de materiales de desecho de diversos campos. Una solución común es utilizar estos materiales como sustituyentes parciales de la fracción inerte en hormigones y morteros. Este trabajo se enfoca en el posible uso de conchas marinas Acanthocardia tuberculata, que constituyen un desperdicio de alimentos destinados al relleno sanitario, como sustituyente parcial del inerte del mortero. Los resultados obtenidos evidenciaron que la reducción de las propiedades mecánicas (en términos de tenacidad y resistencia a flexión) se debe principalmente a las propiedades de absorción de agua de las conchas marinas, que afectan la hidratación del cemento. Sin embargo, como se demostró experimentalmente, dicha disminución de las propiedades mecánicas en cualquier caso no compromete el rendimiento del material cuando viene empleado en aplicaciones civiles.

espanolThe continuous research of new functional materials combining both advanced properties and increased sustainability has dramatically risen up in the last decades. Instead of searching for new solutions, composites (formed by a combination of already present materials) are subject of different studies due to their capability of merging the advantages of components. Hence, chitosan, a biowaste-derived biopolymer, has been thermally-converted into chars by pyrolysis treatment. Subsequently, both chitosan and its char are introduced into cementitious matrix forming cement-based composites. The analysis of the mechanical properties of these materials evidenced that char-containing composites show an incipient fracture toughness capability, very appealing for possible structural applications. EnglishLa investigacion continua de nuevos materiales funcionales que combinan propiedades avanzadas y una mayor sostenibilidad ha aumentado dramaticamente en las ultimas decadas. En lugar de buscar nuevas soluciones, los compuestos (formados por una combinacion de materiales ya presentes) estan sujetos a diferentes estudios debido a su capacidad de fusionar las ventajas de los dos componentes. El quitosano, un biopolimero derivado de residuos biologicos, se ha convertido termicamente en carbon mediante tratamiento de pirolisis. Posteriormente, tanto el quitosano como su carbon se introducen en una matriz cementosa que forma compuestos a base de cemento. El analisis de las propiedades mecanicas de estos materiales puso de manifiesto que los compuestos que contienen carbon muestran una incipiente capacidad de resistencia a la fractura, muy atractiva para posibles aplicaciones estructurales.

This work focused on the recycling of WEEE plastic waste as a partial substitute for aggregate in light mortars. The plastic mix, provided by the IREN group, was used as a replacement of aggregate in 15, 30, 45, 60, 75, and 90%vol in mortars. Worsening of the mechanical performance of around 50% was detected already at only 15%vol of mineral aggregate substituted with plastic waste. The explanation of this phenomenon was found in both the scarce mechanical properties of the used plastic and in the poor adhesion between matrix and plastics that resulted in extra-porosity formation, as also demonstrated by comparing the results with several models in the literature. However, the use of plastic waste as a partial replacement of natural aggregate contributes to the preservation of natural resources and, in any case, does not limit the application of these materials in non-structural applications.

The functionalization of carbon nanotubes (CNTs) is a very important step in many applications but it is still a very complex and variable task. This work shows an efficient, easily reproducible and optimal method to introduce oxygenated functional groups to CNTs by treating them for 60′ at 350 °C with a mixture of 2% oxygen in argon. The oxidized nanotubes were characterized through FT-IR, Raman and TGA to verify the quality of the oxidation and the lattice integrity of the treated CNTs. The results demonstrate that the treated nanotubes are not damaged even after introducing a significant number of new groups. This methodology could be easily tuned to functionalize other types of graphitic materials.

Cement composites were realized containing graphene-based materials having different oxygen content (from 0 to 45%). It was found that the polarity of the reinforcement influences both the dispersion in water and the chemical interaction with the hydrated cement matrix, and thus the mechanical performance of the composites. In particular, the reinforcements with the highest oxygen content result aggregated while the cement with the highest strength is obtained with functionalized graphene, containing 5% oxygen, where the surface has sufficient polar groups to guarantee proper dispersion and interaction with the hydrated cement.

Biogenic amines are a group of important organic bases involved in the metabolism of living organisms and present in biological fluids, food or beverages. Their identification and quantification represent relevant issues in the field of bio-analytical and food chemistry. Beyond the traditional detection techniques, other methods have been recently exploited, as enzymatic-based systems. Herein, diamine-oxidase (DAO) and soybean peroxidase (SBP) were immobilized onto silica spherical monoliths (prepared from biowaste-derived substances) to realize a practical and fast enzymatic system, able to quantify biogenic amines in solution. The mechanism consisted in the oxidation of amines by DAO with the formation of H2O2, which in turn activated the SBP reaction producing an indamine dye. The amount of amine was indirectly determined by the spectroscopic measurement of the final product. Preliminary kinetic tests on DAO/SBP catalytic system using histamine as DAO substrate showed the maximum activity at pH 8. Furthermore, the stability of the functionalized monoliths over several reaction cycles and their catalytic action towards cadaverine, tyramine, tyrosine and histamine were studied. The results showed that the immobilized DAO/SBP system was effective in the determination of different substrates for many cycles, reaching a detection limit comparable to chromatographic methods.

This study evaluates the effectiveness of using different plasma treatments to favor the compatibility between rubber and a cement matrix in composites, thus leading to a different surface reactivity of the rubber component. Plasma-treated rubbers were introduced into two different types of concrete. Mechanical tests highlighted that Portland concrete composites filled with N2/H2 plasma-treated rubber had increased flexural strength, toughness, and compression strength compared to composites containing untreated rubber. A scaling law is also proposed to qualitatively discriminate between related effects due to topological/roughness or intrinsic/chemical adhesion modifications. Plasma treatment can improve both intrinsic adhesion and roughness of the rubber–cement interface and thus the overall concrete strength and toughness.

The lack of robust and low-cost sorbent materials still represents a formidable technological barrier for long-term storage of (renewable) thermal energy and more generally for Adsorptive Heat Transformations—AHT. In this work, we introduce a novel approach for synthesizing cement-based composite sorbent materials. In fact, considering the number of available hygrosopic salts that can be accommodated into a cementitious matrix—whose morphological properties can be also fine-tuned—the new proposed in situ synthesis paves the way to the generation of an entire new class of possible sorbents for AHT. Here, solely focusing on magnesium sulfate in a class G cement matrix, we show preliminary morphological, mechanical and calorimetric characterization of sub-optimal material samples. Our analysis enables us to theoretically estimate one of the most important figures of merit for the considered applications, namely the energy density which was found to range within 0.088–0.2 GJ/m3 (for the best tested sample) under reasonable operating conditions for space heating applications and temperate climate. The above estimates are found to be lower than other composite materials in the literature. Nonetheless, although no special material optimization has been implemented, our samples already compare favourably with most of the known materials in terms of specific cost of stored energy. Finally, an interesting aspect is found in the ageing tests under water sorption-desorption cycling, where a negligible variation in the adsorption capability is demonstrated after over one-hundred cycles.

Since waste tires constitute a serious environmental concern, several studies are devoted to the use of finely divided recycled rubber for the production of rubberized concrete by partial substitution of the mineral aggregate fraction. The introduction of rubber into concrete presents several advantages (e.g., improvement of toughness and thermal/electrical/acoustic insulation capacities). Unfortunately, the addition of a high content of rubber into concrete causes an important loss of mechanical resistance of the final composite. In this context, several scientific studies are devoted to investigate the best technical solutions for favoring the interfacial adhesion between rubber and cement paste, but the interpretation of the literature is often misleading. To overcome this issue, the metadata extrapolated from the single scientific works were critically re-analyzed, forming reference diagrams where the variability fields of the different rubber concrete formulations (in terms of mechanical responses as a function of the rubber content) were defined and the best performances discussed. This study evidenced the twofold role of reference diagrams, able in both presenting the data in an unambiguous manner (for a successful comparison) and providing the guidelines for future works in this research field.

The purpose of this work is the reuse of polyvinyl chloride (PVC) deriving from waste electrical and electronic equipment (WEEE) used as a partial substitute for the mineral aggregate to produce lightened mortars. PVC was recovered from copper electrical cables, ground and used as replacement of mineral aggregate in 5, 10, 15 and 20 % vol. in mortar. A thermal characterization of the starting material was carried out to understand its composition. The mortar samples were mechanically tested both using class G cement and ordinary Portland cement. The results showed a worsening of the mechanical properties of around 50 % for only 5 % in volume of sand substituted with PVC waste. A likely explanation to this phenomenon was found in the mechanical characteristics of the PVC used and to its poor adhesion with the matrix, that resulted in the creation of porosity. However, the mortar prepared contributes to the conservation of natural resources and maintains mechanical properties adequate for the use in non-structural applications (e.g. screed or substrate).

Even if the carbon nanotubes (CNTs) and their derivatives are commonly used as reinforcing phase in composite materials, also in commercial products, their tendency to agglomerate generally determines a scarce dispersion, thus not maximizing the effect due to the second phase. In this article, a perfect dispersion of highly entangled nanotubes was achieved by using a very simple approach: exploiting the dispersing effect of a low-cost polymer, polyvinyl butyral (PVB), coupled with standard ultrasound sonication. Several dispersion approaches were tested in order to develop a consistent and widely applicable dispersion protocol. The tape casting technology was subsequently used to produce 100 to 300 μm thick PVB-matrix composite tapes, reinforced by multiwall CNTs dispersed according to the optimized protocol. Their mechanical properties were evaluated, and a simple model was used to demonstrate that the effective dispersion of CNTs is the key to obtain significantly improved properties.

Graphene is a new generation material, which finds potential and practical applications in a vast range of research areas. It has unrivalled characteristics, chiefly in terms of electronic conductivity, mechanical robustness and large surface area, which allow the attainment of outstanding performances in the material science field. Some unneglectable issues, such as the high cost of production at high quality and corresponding scarce availability in large amounts necessary for mass scale distribution, slow down graphene widespread utilization; however, in the last decade both basic academic and applied industrial materials research have achieved remarkable breakthroughs thanks to the implementation of graphene and related 1D derivatives. In this work, after briefly recalling the main characteristics of graphene, we present an extensive overview of the most recent advances in the development of the Li-ion battery anodes granted by the use of neat and engineered graphene and related 1D materials. Being far from totally exhaustive, due to the immense scientific production in the field yearly, we chiefly focus here on the role of graphene in materials modification for performance enhancement in both half and full lithium-based cells and give some insights on related promising perspectives.

Photo-polymerization is a polymerization method widely exploited in many technological fields, due to its high versatility and fast reaction rates. In this study, poly(ethylene glycol) methacrylate (PEGMA) nanostructures are grown onto cellulose following a simple and promising light-driven reaction mechanism involving benzophenone (as photo-initiator) and UV-curing. The effectiveness of the surface functionalization has been determined by means of morphological and physicochemical characterizations, showing the formation of very sharp PEGMA nanometric architectures.

In this work, we reported the conversion though carbothermal process of two catalysts produced by pyrolyzing exhausted coffee and waste tires. We tailored the surface with anchored iron nanoparticles through a facile carbothermal route and tested them for catalytic oxidative desulphurization of high sulphur content oil derived from tires pyrolysis. We studied their activity in a biphasic system under different conditions reaching a desulphurization of up to of 60% by using an oil with a sulphur concentration of up to 7139 ppm. The extensive characterization proved the reliability of those materials as promising catalysts for upgrading of sulphur rich drop-in fuels.

Despite their promising thermo-physical properties for direct solar absorption, carbon-based nanocolloids present some drawbacks, among which the unpleasant property of being potentially cytotoxic and harmful to the environment. In this work, a sustainable, stable and inexpensive colloid based on coffee is synthesized and its photo-thermal properties investigated. The proposed colloid consists of distilled water, Arabica coffee, glycerol and copper sulphate, which provide enhanced properties along with biocompatibility. The photo-thermal performance of the proposed fluid for direct solar absorption is analysed for different dilutions and compared with that of a traditional flat-plate collector. Tailor-made collectors, opportunely designed and realized via 3D-printing technique, were used for the experimental tests. The results obtained in field conditions, in good agreement with two different proposed models, show similar performance of the volumetric absorption using the proposed coffee-based colloids as compared to the classical systems based on a highly-absorbing surface. These results may encourage further investigations on simple, biocompatible and inexpensive colloids for direct solar absorption.

In this study, cellulose fibers were chemically functionalized under mild conditions by introducing palmitate groups in order to produce a hydrophobic cellulose-based ester. The effectiveness and the degree of functionalization were evaluated by FTIR spectroscopy and thermogravimetric analysis, whereas the structural integrity was confirmed by XRD measurements. The prepared materials were tested in water remediation processes from fatty oils mixtures from both animal (cod liver oil) and vegetable (sunflower oil) sources. Experimental kinetic measurements, rationalized by means of the most common models, show that the best performances were reached toward the sunflower oil, hence proving the promising application of such green materials as a sustainable alternative tool for oil–water remediation processes.

Carbon fibers can be used to improve both mechanical properties and electrical conductivity of cement, allowing the preparation of a strengthened and toughened cement that can be used for self-monitoring applications. To guarantee both a good dispersion in water and a strong interaction with cement, surface functionalization of carbon fiber surface by reaction with acid was preferred to the use of a dispersing agent. The best oxidation conditions were chosen by using a Taguchi approach, and the samples contained the treated fibers were subjected to both mechanical and electrical tests, to determine flexural strength, toughness, compressive strength and electrical conductivity. It was shown that a not-too-strong oxidation by piranha solution was very effective to obtain well-dispersed fibers and a cement-composite with improved mechanical properties (in particular toughness) and electrical conductivity.

Bioinspiration can lead to exceptional mechanical properties in a number of biological materials as a result of their internal structure. In particular, the hierarchical arrangement of nano-to macro-components can bring to complex energy dissipation mechanisms and unprecedented resistance to crack growth. In this work, we propose to exploit this approach, combining in a multiscale composite structure carbon nanotubes with conventional carbon fibre reinforcements in a polyvinyl butyral matrix. We show that grafting the nanotubes onto the carbon microfibres improves their interface properties with the matrix considerably, effectively doubling their apparent strength. At the same time, the addition of nanotubes to microfibre reinforcements helps to improve the composite toughness, reaching more than twice the value for the conventional, non-hierarchically reinforced composite. Numerical simulations and fracture mechanics considerations are also provided to interpret the results.