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GRAPHICAL ABSTRACT ABSTRACT Alkali activated lightweight mortars, obtained by room temperature activation of coal fly ash, were studied as passive fire protection systems for steel elements. Physical, mechanical and thermal [...]

ABSTRACT Air--and formulated lime mortars with pulverized brick waste were synthesized with addition of two organic waste-based additives: spent cooking oil and albumen. The addition of spent oil in the [...]

ABSTRACT This paper investigates the shrinkage and creep of self-compacting concrete prepared with coarse and fine recycled concrete aggregates (up to 40% of total amount of aggregates). Physical properties and [...]

ABSTRACT Glass with different chemical compositions, deriving from separate collection, has been used as fine aggregate to formulate cementitious mortars, substituting natural sand. Glass coming from cathode-ray tube monitors, fluorescent [...]

ABSTRACT The suitability of new lime mortars for restorative rendering applications was investigated. Air-, formulated- and hydraulic-lime mortars were synthesized with inclusion of two different types of spent sunflower cooking [...]

ABSTRACT This work investigates the effects of the structure, the bulk chemical composition and amount of the aluminosilicate fines on the strength development, pore refinement, water permeability, moisture control capacity [...]

ABSTRACT Alkali activation of fly ash can be considered as one of the more promising alternative systems to traditional hydraulic binders, particularly if the process can be carried out at [...]

ABSTRACT The effects of bulk composition and microstructure on strengthening mechanisms and fracture resistance were investigated for metakaolin based geopolymers. Crack initiation and propagation under mechanical and environmental stresses were [...]

Alkali activated materials and geopolymers have attracted a lot of attention in the last 20 years thanks to their excellent mechanical performances, durability and sustainability properties, especially for civil applications. These materials also exhibit promising properties as fire- and corrosion-resistant protection systems. In a previous study, a 20-mm coating based on light-weight alkali activated mortar (LWAAM) suitable for the protection of steel structures against fire was successfully developed. To understand if the same coating is also able to ensure corrosion protection to steel structures, this study reports the results obtained in two different chloride-rich environments. The corrosion performance of the new system based on steel coated by LWAAM (using expanded perlite and hydrogen peroxide in the mix) was compared with a steel coated by a traditional alkali activated mortar (NWAAM). Electrochemical tests on steel samples immersed in an alkaline solution simulating the pore environment of the binder or embedded in the two different types of mortars were carried out in presence of different chloride concentrations. It was found that the alkaline environment is able to passivate the steel surface, however, the increasing of chloride ions concentration, affects passive film stability and promotes steel corrosion. In presence of low chloride concentration (i.e., 0.2M NaCl), the increased porosity of the LWAAM did not impair the steel corrosion protection, when compared with NWAAM.

The authors regret to communicate that one author name has not been identified correctly. Correct identification of Maria Chiara Bignozzi 'name' and 'surname' Correct name: Maria Chiara Correct surname: Bignozzi [...]

Geopolymers are hydrated aluminosilicates with excellent binding properties. Geopolymers appeal to the construction sector as a more sustainable alternative to traditional cements, but their exploitation is limited by a poor understanding of the linkage between chemical composition and macroscopic properties. Molecular simulations can help clarify this linkage, but existing models based on amorphous or crystalline aluminosilicate structures provide only a partial explanation of experimental data on the nanoscale. This paper presents a new model for the molecular structure of geopolymers, in particular for nanoscale interfacial zones between crystalline and amorphous nanodomains, which are crucial for the overall mechanical properties of the material. For a range of Si–Al molar ratios and water contents, the proposed structures are analyzed in terms of skeletal density, ring structure, pore structure, bond-angle distribution, bond length distribution, X-ray diffraction, X-ray pair distribution function, elastic moduli, and large-strain mechanics. Results are compared with experimental data and with other simulation results for amorphous and crystalline molecular models, showing that the newly proposed structures better capture important structural features with an impact on mechanical properties. This offers a new starting point for the multiscale modeling of geopolymers.

The ceramic tile industry is one of the most important industrial sectors in Italy, with almost 90% of the whole production located in the Emilia-Romagna region. In this paper, the waste management and recycling practices in force among Italian ceramic tile manufacturers are re-ported and discussed on the basis of performance indicators determined thanks to the elaboration of a large amount of industrial data collected in the period 2013–2020. In particular, parameters such as annual water consumption (Cw) and demand (Dw), recycling factor of solid waste (Rsw) and water (Rw) and different kinds of waste generated in the process have been monitored for three different production layouts. Such indicators exhibit that recycling is a well-established practice in Italian ceramic tile production and only a minor amount of hazardous waste (exhausted lime) is land-filled.

Foaming methods to reduce the density of geopolymers were investigated as low density geopolymers are increasingly being reported in the literature to be effective in improving the insulating properties. However, there is no consistency in foaming methods and as such this study was performed to compare different foaming agents in order to better understand their effect on the properties of geopolymers. In particular, a surfactant and hydrogen peroxide were used individually and in combination to ensure a homogeneous pore distribution in the slurry. Physical and microstructural properties of the hardened low density geopolymers are presented and discussed. The behaviour under fire conditions of fibre reinforced and foamed geopolymer samples will also be presented in order to appreciate the suitability of geopolymer composite in high temperature applications.

The growing focus on issues related to the control of CO2 emissions, energy conservation and waste recycling pushes the construction industry to tackle the challenge of sustainable development. The production of ordinary Portland cement (OPC), main product of the sector, is one of the most polluting in terms of CO2 emissions, thus finding alternative binder is becoming an urgent matter. Geopolymers are largely investigated for this purpose, but studies concerning the durability of reinforced conglomerates prepared with alkali activated binders are only few. The present work aims at investigating the durability performances of steel reinforced geopolymer mortar samples based on carbon fly ash in comparison with OPC mortar. The effect of different Na2O/SiO2 molar ratios in the geopolymer mixes is evaluated in terms of mechanical and microstructural properties as well as corrosion resistance in a chloride rich environment. The obtained results show that under the same severe environmental conditions more limited chloride amounts penetrate in reinforced fly-ash geopolymers where a better corrosion behaviour is also detected up to a week of exposure for samples with a nominal Na2O/SiO2 molar ratio equal to 0.12 and 0.14. Instead, the corrosion resistance is quite similar to that of reinforced OPC mortar when a period of three months is considered.

Geopolymers, and more in general alkali activated materials (AAM), are a new class of materials obtained by alumino-silicates precursors activated by means of alkaline solutions. Indeed, the term geopolymers is usually strictly referred to pure alumino-silicates such as metakaolin as starting material, whereas when the precursors also contain calcium oxide the resulting products are usually defined AAM. Geopolymerization technology can be more easily considered a sustainable process when industrial waste is used as precursors and the consolidation process occurs at room temperature. With these premises, alkali activation may be a very promising technology for the ceramic sector as well as construction industry. In this work, waste coming from bricks production has been used to obtain, at room temperature, geopolymers with different porosity tuning the sodium silicate content in the feed. Microstructure analysis carried out by means of mercury intrusion porosimeter and scanning electron microscopy is reported and discussed.

Electric arc furnace slag (EAF-S), coming from a steel productive plant in Italy, has been used as new source for geopolymers synthesis. The slag has been geopolymerized alone and with different content of metakaolin (MK) with the aim to investigate if EAF-S content plays a role in geopolymerization process. Mechanical properties results and microstructure analysis highlight that the optimum weight ratio MK/EAF-S to be used as starting materials is 40/60, 30/70, 20/80. Moreover EAF-S, when used with MK, directly participates in the formation of calcium-rich alumino-silicate gels.

Foaming methods to reduce the density of geopolymers were investigated as low density geopolymers are increasingly being reported in the literature to be effective in improving the insulating properties. However, there is no consistency in foaming methods and as such this study was performed to compare different foaming agents in order to better understand their effect on the properties of geopolymers. In particular, a surfactant and hydrogen peroxide were used individually and in combination to ensure a homogeneous pore distribution in the slurry. Physical and microstructural properties of the hardened low density geopolymers are presented and discussed. The behaviour under fire conditions of fibre reinforced and foamed geopolymer samples will also be presented in order to appreciate the suitability of geopolymer composite in high temperature applications.

The growing focus on issues related to the control of CO2 emissions, energy conservation and waste recycling pushes the construction industry to tackle the challenge of sustainable development. The production of ordinary Portland cement (OPC), main product of the sector, is one of the most polluting in terms of CO2 emissions, thus finding alternative binder is becoming an urgent matter. Geopolymers are largely investigated for this purpose, but studies concerning the durability of reinforced conglomerates prepared with alkali activated binders are only few. The present work aims at investigating the durability performances of steel reinforced geopolymer mortar samples based on carbon fly ash in comparison with OPC mortar. The effect of different Na2O/SiO2 molar ratios in the geopolymer mixes is evaluated in terms of mechanical and microstructural properties as well as corrosion resistance in a chloride rich environment. The obtained results show that under the same severe environmental conditions more limited chloride amounts penetrate in reinforced fly-ash geopolymers where a better corrosion behaviour is also detected up to a week of exposure for samples with a nominal Na2O/SiO2 molar ratio equal to 0.12 and 0.14. Instead, the corrosion resistance is quite similar to that of reinforced OPC mortar when a period of three months is considered.

Geopolymers, and more in general alkali activated materials (AAM), are a new class of materials obtained by alumino-silicates precursors activated by means of alkaline solutions. Indeed, the term geopolymers is usually strictly referred to pure alumino-silicates such as metakaolin as starting material, whereas when the precursors also contain calcium oxide the resulting products are usually defined AAM. Geopolymerization technology can be more easily considered a sustainable process when industrial waste is used as precursors and the consolidation process occurs at room temperature. With these premises, alkali activation may be a very promising technology for the ceramic sector as well as construction industry. In this work, waste coming from bricks production has been used to obtain, at room temperature, geopolymers with different porosity tuning the sodium silicate content in the feed. Microstructure analysis carried out by means of mercury intrusion porosimeter and scanning electron microscopy is reported and discussed.

Electric arc furnace slag (EAF-S), coming from a steel productive plant in Italy, has been used as new source for geopolymers synthesis. The slag has been geopolymerized alone and with different content of metakaolin (MK) with the aim to investigate if EAF-S content plays a role in geopolymerization process. Mechanical properties results and microstructure analysis highlight that the optimum weight ratio MK/EAF-S to be used as starting materials is 40/60, 30/70, 20/80. Moreover EAF-S, when used with MK, directly participates in the formation of calcium-rich alumino-silicate gels.

Two new series of liquid crystalline poly(glycidyl ether)s I and II containing a side-chain 4-alkoxy-azobenzene mesogenic unit were prepared according to two different synthetic routes. The former were prepared by ring-opening anionic polymerization of different mesogenic epoxides, while the latter were prepared by grafting the same mesogenic side chain onto preformed poly(epichlorohydrin) to different substitution extents. Poly(glycidyl ether)s I formed a sequence of different smectic mesophases and nematic mesophases, depending on the length of the alkoxy tail. For poly(glycidyl ether)s II the kind of the phase behavior (not liquid crystalline, nematic, nematic and smectic) was strongly correlated with the extent of mesogenic side-chain incorporation with greater degrees of substitution favoring the onset of more stable and ordered mesophases. No smectic monolayer arrangement was observed, but only bilayer smectic structures, either SA2Or SC2, were detected by X-ray diffraction investigations on powder or magnetically aligned samples.

A new type of block copolymers comprising both main-chain and side-chain liquid-crystalline (LC) blocks in the same macromolecular structure was synthesized and studied. The former was a semiflexible LC polyester block, and the latter was an LC polymethacrylate block. Thermal, dynamic-mechanical, and X-ray diffraction data indicated that the two structurally different blocks were partly phase-separated in the glassy and LC states. Significant deviations of the transition temperatures and enthalpies were observed relative to those of the corresponding homopolymers.

The molecular organization in the smectic mesophases of a series of main-chain/side-chain block copolymers was studied by X-ray diffraction on oriented specimens. The main-chain and the side-chain blocks were phase-separated and gave rise to two coexisting smectic domains with different layer periodicities. The orientation of the smectic planes in the distinct domains with respect to the fiber axis was very different in the various samples and depended on the relative length of the blocks. In the presence of relatively short side-chain blocks, the orientation of the main-chain block dominated and the smectic planes of the side-chain block were forced to be parallel to those of the main-chain block and perpendicular to the fiber axis. In contrast, when the side-chain block was sufficiently long it imposed its own orientation to the main-chain block. In this case, the smectic planes of the main-chain block were oriented parallel to those of the side-chain block and to the fiber axis.

One-part or “just add water” alkali activated materials (AAMs) have attracted a lot of attention thanks to the use of solid alkaline activators that makes these materials more suitable to commercialization compared to conventional AAMs (two-part). This is mainly because large quantities of caustic solutions should be handled for producing conventional AAMs. So, one-part AAMs have a great potential for in-situapplications. However, heat curing (<100 °C) has been demonstrated to be the best condition to obtain optimized performances of one-part AAMs. This study investigates how to obtain high strength one-part alkali mortars cured at room temperature, considering a newly developed mix design, precursor pre-treatments and curing time. The mechanical performances (i.e.,elasticity modulus, compressive and flexural strength) of the developed materials were reported, as well as physical properties, in terms of water absorption, open porosity and pore size distribution and microstructure (by means of FEG-SEM observations coupled with elemental analysis by EDS and FT-IR measurements). Class F fly ash have been activated by potassium hydroxide and anhydrous sodium metasilicate. It was found that high strength one-part AAMs can be achieved by activating coal fly ash with a mix of KOH and anhydrous sodium metasilicate at room temperature. In particular, room temperature-cured one-part mortars obtained by pre-treated fly ash exhibited mechanical performance similar to those obtained by heat-cured mortars (at 70 °C, tested after 7 days), reaching a compressive strength (Rc) greater than 60 MPa at 28 days of curing when mechanochemical activation of fly ash was applied.