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This study evaluates the mechanical performance of ambient-cured fly ash-based geopolymer composites reinforced with recycled glass fibers. First, the Taguchi method was used to optimize the fly ash-based geopolymer matrix, considering the Na:Al ratio, liquid:solid ratio, and sand content. Secondly, two types of glass fibers (25 mm length and 60 mm length) have been introduced in three different amounts (1, 2, and 3 wt. %, respectively) in order to improve the flexural strength of the developed composites. Compressive strength tests and the three-point flexural method were conducted to demonstrate the effect of fiber type and amount on the mechanical performances of fly ash-based geopolymers, while microstructural analysis was used to reveal the improving mechanism caused by the bridging effect of reinforcing fibers. Experimental results showed that Na:Al of 0.75, NaOH concentration of 10.85M, Na2SiO3:NaOH solution of 4:1, and Sand:Fly ash of 1:1 are the optimum parameters for compressive strength, while Na:Al of 0.5, NaOH concentration of 2.96M, Na2SiO3:NaOH solution of 2:1, and Sand:Fly ash of 1:4 exhibit the highest flexural strength, despite the aging time (14 or 28 days). Moreover, the addition of recycled glass fiber led to an increase of up to eight times in flexural strength due to the bridging effect. However, the compressive strength slightly decreased for all mixtures due to an increase in porosity. The microstructural analysis confirmed a homogenous matrix with high adhesion to the surface of glass fibers. [ABSTRACT FROM AUTHOR]

This paper aims to study the possibility of improving the chemical and surface characteristics of the Ti6Al4V alloy by depositing phosphate layers on its surface. Accordingly, an innovative phosphating solution was developed and used in a chemical conversion process to obtain Ca–Zn phosphate layers on the base material surface. Moreover, the chemical composition of the phosphate solution was chosen considering the biocompatibility of the chemical elements and their possibility of contributing to the formation of phosphate compounds. The obtained layer was characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and potentiodynamic polarization tests. The wetting of the Ca–Zn sample surface was also investigated using water and two liquids similar to body fluids, namely, Ringer and Dulbecco solutions. According to the surface energy study, the polar component is almost two times larger compared with the dispersive one. The SEM and EDS tests revealed a uniformly coated surface with intercalated crystals leading to a rough surface. Furthermore, the XRD results showed not only the presence of hopeite and scholzite but also of phosphophyllite. By the vibrations of the PO4−3 groups, the FTIR test confirmed the presence of these phases. The potentiodynamic tests revealed that the samples coated with the Ca–Zn phosphate layer present better corrosion resistance and a lower corrosion rate compared with the uncoated ones. [ABSTRACT FROM AUTHOR]

In a continuously changing world where the human operator still plays an important role in most industrial activities, health and safety occupies a fundamental place, with the goal of maintaining workers healthy and in safe condition during their job activities. One of the means that make this goal achievable is the use of adequate personal protective equipment. The carabiners are connecting parts that link the components quickly and reversibly of personal protective equipment used against falls. Thus shackles can be divided in multiple elements, such as: the gate, which always opens inward and can be provided with or without the locking system, the second and the biggest element is the body which can have different form according to the BS EN 12275:2013 standard, the gate and the body are connected thru the rivet pin and nose. The personal fall arrest system used in areas such as construction, speleology, petroleum industry, includes metal components that must possess high mechanical properties, especially shock-resistance. In order to improve resilience, a layer of rubber paint will be deposited on the carabiner surface. The aim of this study is to analyse the influence of rubber coating on the carabiners shock resistance.

The ESD method (electro spark deposition) is used to cover through deposition the active parts of machines, working in heavy abrasive wear moist environment as well as in a dry environment. The paper proposes the use ESD method for Fe-C alloys for obtaining thin layers system with physical-mechanical properties improved comparing to base material. Due to polar effect, the predominant transfer of anode's material (electrode) towards cathode (piece) assures the forming of the superficial layer with well-determined physical -chemical properties. In addition, in multiple layers case the deposit of a supplementary layer emphasizes the diffusion of the first deposited layer by anchoring more the coating. [ABSTRACT FROM AUTHOR]

Coal ash-based geopolymers with mine tailings addition activated with phosphate acid were synthesized for the first time at room temperature. In addition, three types of aluminosilicate sources were used as single raw materials or in a 1/1 wt. ratio to obtain five types of geopolymers activated with H3PO4. The thermal behaviour of the obtained geopolymers was studied between room temperature and 600 °C by Thermogravimetry-Differential Thermal Analysis (TG-DTA) and the phase composition after 28 days of curing at room temperature was analysed by X-ray diffraction (XRD). During heating, the acid-activated geopolymers exhibited similar behaviour to alkali-activated geopolymers. All of the samples showed endothermic peaks up to 300 °C due to water evaporation, while the samples with mine tailings showed two significant exothermic peaks above 400 °C due to oxidation reactions. The phase analysis confirmed the dissolution of the aluminosilicate sources in the presence of H3PO4 by significant changes in the XRD patterns of the raw materials and by the broadening of the peaks because of typically amorphous silicophosphate (Si–P), aluminophosphate (Al–P) or silico-alumino-phosphate (Si–Al–P) formation. The phases resulted from geopolymerisation are berlinite (AlPO4), brushite (CaHPO4∙2H2O), anhydrite (CaSO4) or ettringite as AFt and AFm phases. [ABSTRACT FROM AUTHOR]

Geopolymers, or also known as alkali-activated binders, have recently emerged as a viable alternative to conventional binders (cement) for soil stabilization. Geopolymers employ alkaline activation of industrial waste to create cementitious products inside treated soils, increasing the clayey soils' mechanical and physical qualities. This paper aims to review the utilization of fly ash and ground granulated blast furnace slag (GGBFS)-based geopolymers for soil stabilization by enhancing strength. Previous research only used one type of precursor: fly ash or GGBFS, but the strength value obtained did not meet the ASTM D 4609 (<0.8 Mpa) standard required for soil-stabilizing criteria of road construction applications. This current research focused on the combination of two types of precursors, which are fly ash and GGBFS. The findings of an unconfined compressive strength (UCS) test on stabilized soil samples were discussed. Finally, the paper concludes that GGBFS and fly-ash-based geo-polymers for soil stabilization techniques can be successfully used as a binder for soil stabilization. However, additional research is required to meet the requirement of ASTM D 4609 standard in road construction applications, particularly in subgrade layers. [ABSTRACT FROM AUTHOR]