1,721,065 research outputs found
Induced Modification of Flexural Toughness of Natural Hydraulic Lime Based Mortars by Addition of Giant Reed Fibers
Full text linkNowadays, there is a growing need to reduce the environmental impact generated by the use of inorganic materials for building applications. The aim of this work is to investigate the bio-lime based mortar flexural toughness improvement due to the addition of common reed fibers (Arundo donax L.) in order to evaluate their possible application as ductile eco-compatible prefabricated bricks or laying and joint mortars for masonry. Different sets of specimens were tested by varying the fiber weight content and the fiber length. Moreover, chemical treatments with Linseed Oil and Polyethylene glycol (PEG) were performed to improve the physical and mechanical properties of the fibers as well as the fiber/matrix interfacial adhesion. The Mechanical characterization of the neat and treated fibers was performed through Single Fiber Pull-out Test and Single Fiber Tensile Test. The quasi-static mechanical properties of the composites were evaluated through Three-Point Bending and Compressive tests. Finally, an analytical model proposed in the literature has been used to evaluate the parameters that influence the post-fracture behavior of the composites. Overall, the findings of this study are valuable to understand the flexural behavior of new eco-compatible natural fibers reinforced mortars for masonry application providing scientific evidence of the effectiveness of giant reed fibers in the manufacturing of green building materials, as bricks or laying mortars
Analysis of the chemical and microstructural modifications effects on the hydro-mechanical behaviour of a lime-treated clay
No full textThe paper presents the results of a characterization of kinetic characteristics of pozzolanic reaction with the aim to investigate the time-dependent modification of clay properties as a consequence of mixing with lime. Results of chemical analyses are in agreement with the increase of mechanical properties and with the observed microstructure modifications up to one year of curing time. The rate of development of pozzolanic reactions seems to be almost constant while the time required for their completion is dependent on the lime content. Pozzolanic products are responsible for the time reduction of swelling strain upon saturation as well as for the increases of yielding stress, stiffness and hydraulic conductivity. However, the data analysis proves that a significant component of settlement measured during loading may be induced by the secondary compression process (creep). These results are significant for the prediction of the long-term behaviour of the stabilized soil
Physical and mechanical properties of sustainable hydraulic mortar based on marble slurry with waste glass
Full text linkThis paper aims to propose and characterize a sustainable hydraulic mortar entirely obtained by the reuse of waste materials, with marble slurry coming from quarries in the northwestern Sicily and glass powder coming from a waste collection plant in Marsala (Province of Trapani). The first was used as raw material to produce the mortar binder by a kilning and slaking process, while the second was used as a pozzolanic additive. The chemical and morphological characterization of the marble slurry was done by XRD, FTIR, STA and SEM analyses. Glass powder was analyzed through particle size distribution measurements, XRD and standard pozzolanic tests. Hydraulic mortars constituted by slaked lime from kilned marble slurry and waste glass powder (LGS) were prepared beside commercial Natural Hydraulic Lime (NHL) based mortars (NGS) and air-hardening lime (LSS)-based mortars. Mechanical and absorption properties of the mortars were investigated as a function of the grain size of the glass powder by means of three-point bending and compressive strength tests, capillary uptake, helium pycnometry and simultaneous thermal analysis. The results demonstrated that the formulation LGS exhibits significantly improved mechanical and absorption properties compared to air-hardening mortars (LSS). It confirms the possibility of producing a more sustainable hydraulic mortar exclusively from waste materials for civil engineering
Semiconducting properties of passive films and corrosion layers on weathering steel
No full textAnodic films were grown on Weathering Steel by potentiostatic polarization in slightly alkaline solution. The photoelectrochemical results reveal that they are n-type iron oxide with Eg = 2.0 eV. Rust layer grown by atmospheric corrosion are n-type semiconductors with a band gap higher than that estimated for the anodic film attributed to the formation of γ-lepidocrocite. The electrochemical impedance spectra allow to evidence that rust layers have a higher conductivity with respect to anodic films due to the presence of highly doped iron oxide layers. The use of Mott-Schottky theory to model the dependence of oxide capacitance as function of potential is critically discussed
Comparison of thermal expansion of wood and epoxy adhesives
No full textEpoxy-based adhesives are used both in the consolidation of decayed timbers and for new structural joints. Investigating the compatibility of wood and epoxy adhesives provides a better knowledge of the long-term behaviour of wood-epoxy joints. Besides mechanical compatibility, also temperature-related parameters are relevant in this context. The values of the thermal expansion coefficients (TEC) of two wood species (Spruce, Picea abies and Iroko, Clorophora excelsa) and four different epoxy resins have been compared using a modified test method that allows for nearly iso-hygric conditions of the wood specimens. Minor differences in TEC have been observed between wood in the transversal-to-the-grain direction and an experimental epoxy adhesive, which is considered highly compatible with wood on the basis of mechanical and ageing tests. Other commercial epoxy adhesives show greater differences in terms of TEC and a proportionally decreasing mechanical compatibility. According to these results, the evaluation of thermal properties can be considered very useful for a modelling approach to predict the long term behaviour of wood-epoxy adhesive interface
Studio della resistenza alla corrosione di acciai impiegati nell’industria alimentare e delle bevande
Full text linkIn the present study we performed the physico-chemical characterization of passive films grown on different stainless steel grades after long exposure time in hot purified water (HPW). In order to get more insight into dissolution phenomena that can induce rouging on equipment materials typically involved in food and beverage industries, 304L, 316L and a super duplex 2507 SS samples were passivated at the open circuit potential by different immersion times in HPW at 60°C. Photoelectrochemical and Electrochemical Impedance measurements were performed in the attempt to correlate the electronic properties of the passive films (band gap and conductivity type) to their corrosion resistance
Impact of Surface Treatment on the Strengthening of Geopolymer Composites Reinforced with Short Sisal Fibers
No full textThis paper presents a first-time investigation into the effects of an eco-friendly sodium bicarbonate fiber treatment on the mechanical properties of metakaolin-based geopolymers reinforced with short sisal fibers. For this purpose, geopolymer composites were initially manufactured by replacing different weight contents (0.5–2.0 wt.%) of aggregate (river sand) with untreated natural fibers. Subsequently, sisal fibers were soaked for 120 h in varying concentrations of aqueous NaHCO3 solutions (2.5–10 wt.%) to assess the influence of solution concentration on the performance of 2% fiber-reinforced geopolymer composites. All the manufactured composites were characterized through quasi-static compression, flexural, and Brazilian tests. The experimental results revealed that both increasing the fiber content and pre-treating the sisal fibers significantly affect the mechanical response of the geopolymer composites
Effect of sodium bicarbonate treatment on the properties of sisal fibers and their geopolymer composites
Full text linkEco-friendly and cheap treatments based on the use of mildly alkaline solutions have been recently investigated to modify natural fibers, altering their surface and improving their compatibility mainly with polymer matrices. A challenge for the researchers is nowadays represented by the assessment of this kind of treatments as a viable approach also for geopolymer based composites. In such a context, this study presents a novel and sustainable approach for enhancing sisal fibers for geopolymer composites using a sodium bicarbonate (NaHCO3) treatment. While the treatment offers a greener alternative to conventional methods, its key advantage lies in achieving a balance between fiber properties. Although it slightly reduces raw fiber strength, the NaHCO3 treatment effectively removes impurities, promoting improved crystallinity and, more importantly, significantly enhances fiber surface roughness and homogeneity. This tailored surface modification fosters superior interfacial bonding with the geopolymer matrix, resulting in composites with significantly enhanced flexural toughness (82 %) – a critical property for construction materials – compared to those reinforced with untreated fibers. Flexural strength is also improved by (53 %). This work not only demonstrates the effectiveness of NaHCO3 treatment but also highlights its potential for developing high-performing, eco-friendly construction materials. A comprehensive evaluation, including three-point bending tests to assess toughness, validates this promising approach
One-step electrodeposition of superhydrophobic coating on 316L stainless steel
Full text linkSuperhydrophobic coatings were fabricated through a one-step electrochemical process onto the surface of 316L stainless steel samples. The presence of hierarchical structures at micro/ nanoscale and manganese stearate into the coatings gave superhydrophobicity to the coating, with contact angle of ~160◦, and self-cleaning ability. Corrosion resistance of 316L samples was also assessed also after the electrodeposition process through Electrochemical Impedance Spectra recorded in an aqueous solution mimicking seawater condition
Heterogeneous crystallization of zinc hydroxystannate on galvanized steel for enhancing the bond strength at the rebar/concrete interface
No full textZinc hydroxystannate (ZnSn(OH)6) coatings were deposited on galvanized carbon steel samples by an electroless heterogeneous crystallization process. Structural and morphological features of the coatings as a function of the immersion time were determined by X-ray diffraction, Raman Spectroscopy and Scanning Electron Microscopy revealing the presence of truncated octahedrons of crystalline ZnSn(OH)6. Electrochemical characterization in a simulated concrete pore solution without and with addition of chloride ions proved that the cathodic protection is preserved and that ZnSn(OH)6 improved the corrosion resistance of the rebars. Pull-out tests demonstrated an enhanced bond strength at the rebar/concrete interface and, thus, an improved adhesion after the heterogeneous crystallization process
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