Durability Studies Research Articles

INVESTIGATION ON CORROSION AND FLEXURAL BEHAVIOUR OF REINFORCED CONCRETE USING MARINE SAND

Traditionally, the construction industry relies on both manufactured sand (known as MF-Sand) and river sand as primary constituents for fine aggregates. However, in response to the dwindling supply of river sand, the contemporary preference is firmly in favor of MF-Sand. This research focuses the utilization of meticulously cleaned marine sand (referred to as MR-Sand) as a superior substitute for MF-Sand, aiming to curtail the reliance on and depletion of river sand, a finite natural resource. The objective of this research is to examine the mechanical property of flexural performance of Reinforced Cement Concrete (RCC) Beam and durability study of concrete using corrosion test in which washed MR - Sand as a fine aggregate in partial replacement of MF-Sand from 20% to 60%. The physical and chemical characteristics of treated and untreated marine sand are compared with a view to better comprehending the features of MR and MF-Sand. Experimental research works have been carried out to look into the corrosion test and flexural strength in order to better understanding the strength and durability attributes of concrete. The values for flexural strength, ultimate load, load-deflection, load-strain, and crack pattern have been compared for the RCC beam specimens MF100, MR20, MR40 and MR60. The findings indicate that 60% of MR-Sand possesses the desired properties of strength and durability of concrete. Additionally, Finite Element Analysis is carried out using the ABAQUS software to further validate the experimental findings of load-deflection, load carrying capacity, crack pattern and flexural strength.

Thermal Performance Analysis and Design Evolution of Ventilated Stone Facades: A Case Study of the Praski Student House (Akademik Praski) in Warsaw

The rationale for this work arose from the urgency of improving the energy efficiency of buildings at the design stage, given the changing requirements of energy efficiency standards such as the Polish Technical Conditions (WT 2014 and WT 2020). This research is novel as there is currently limited information available on the improvement of the thermal performance of ventilated stone facade systems, although they are now widely used due to their practical and aesthetic advantages. The first objective of this work is to evaluate the thermal performance of the ventilated facades of the Praski Student House (Akademik Praski) and to assess how certain design variations can help achieve a lower level of energy consumption. Using a comprehensive case study approach, this study provides accurate thermal calculations of the facade to assess its global thermal insulation coefficient (Rt) and thermal transmittance (Uc). The improvement in the actual U-value from the original design is as follows: the U-value is reduced from 0.33 originally to 0.228 for WT 2014 and to 0.198 for WT 2020, showing a reduction of about 30.9% and 13.2%, respectively. These results indicate the energy efficiency of increased insulation thickness and optimally oriented air gap dimensions. The practical contributions of this research are valuable for architects, engineers, and contractors involved in the design and construction process of buildings aiming to achieve near-zero energy buildings (nZEBs), including concrete suggestions on how to improve current construction practices as well as material recommendations. There is a need for durability studies, for example to assess the performance of such facades under different climatic conditions, as part of future work to support these findings.

Performance of Molasses Waste as a Cement Replacement to Study Concrete Compressive Strength

To reduce the negative environmental impact of cement production and preserve natural resources, an experimental investigation was conducted to study the performance of concrete specimens at different curing ages and to determine the compressive strength of these specimens by replacing cement with molasses. Experimentation was carried out on the concrete specimens at a temperature range of 25 °C to 30 °C; six specimens were cast for each replacement ratio, except for 0.75% wt. of cement (86.55 g) and 1% wt. of cement (113.6 g), where five samples were considered for each ratio. The average 28-day compressive strength of the conventional concrete specimens came out to be 29 MPa, but increased to 40 MPa with the addition of 0.25% wt. of cement molasses (28.85 g). It was observed that as the percentage of molasses waste in the concrete mix was further increased by replacing the cement, the compressive strength of the concrete specimens increased gradually and then significantly decreased. The findings shed light on the prospect of using molasses waste instead of cement in the concrete mix. Also, it is worth mentioning that about 30% of the cost–benefit was obtained with reference to that of conventional admixtures available in the market for the production of concrete. However, it is notable that a long-term durability study needs to be conducted before making it viable. This work not only addresses a sustainable and innovative method of waste management (SDG12), but also contributes to low carbon emissions (SDG13). The novelty of this work lies in the fact that no such kind of study has been conducted in Pakistan so far, in addition to the very limited international literature available, and, in particular, no evidence on the compressive strength results at higher molasses dosages, i.e., 1% wt. of cement (113.6 g) and 2% wt. of cement (230.8 g).

Enhanced Pozzolanic Activity of Crushed Brick Powder with Hydrated Lime: Concrete Durability Study

Enhanced Pozzolanic Activity of Crushed Brick Powder with Hydrated Lime: Concrete Durability Study

Population-level health impact of hypothetical waning 1-dose human papillomavirus vaccination and 2-dose mitigation strategies in a high cervical cancer burden setting

Abstract Background We simulated the impact of hypothetical waning scenarios of a 1-dose human papillomavirus (HPV) vaccination paired with switching to 2-dose mitigation strategies guided by empirical vaccine trial reporting timelines. Methods Using 2 independent mathematical models fitted to a high-burden setting, we projected the cumulative cervical cancer cases averted over 85 years for alternative HPV vaccination scenarios under 2 program adoption timelines: 1) de novo introduction of a 1-dose HPV vaccination and 2) a switch from an existing 2-dose HPV vaccination program to a 1-dose vaccination. We assumed 80% vaccination coverage with the bivalent vaccine and an average duration of a 1-dose HPV vaccine protection of either 30 or 25 years with 100% efficacy. We varied the eligible age group(s) at program introduction and the 2-dose mitigation (single-age cohort or multi-age cohort). If needed for mitigation, reintroduction of 2-dose vaccination was assumed to occur in 2036 (ie, 30 years after initiation of the Costa Rica Vaccine Trial). Results Under both vaccine adoption timelines, the models projected that countries could achieve the same level of health benefits by switching to 2 doses in 2036 using a multi-age cohort approach as with initiating a 2-dose or 1-dose vaccination program with no waning. With only a single-age cohort 2-dose mitigation approach, 98%-99% of cases would be prevented compared with the health benefits of 2 doses or a noninferior, durable 1 dose. Conclusions Countries hesitant to adopt a 1-dose HPV vaccination program may have opportunities to leverage the benefits and efficiency of a 1-dose schedule while awaiting longer-term reporting from 1-dose durability studies, including Costa Rica Vaccine Trial.

Carbon-Capped PtNi Catalysts for the Oxygen Reduction Reaction in Acidic Environment: A Durability Study

Carbon-Capped PtNi Catalysts for the Oxygen Reduction Reaction in Acidic Environment: A Durability Study

Strength and Durability Studies on Concrete Utilizing Sewage Sludge Ash and Treated Sewage Water

The effects of incorporating sewage sludge ash and treated sewage water on the strength and durability of concrete, with the goal of evaluating their viability as sustainable alternatives in construction materials. The sewage sludge ash was used as a replacement material to cement after burning of sewage sludge with high temperature of 800oC. So obtained sewage sludge ash was analysed for chemical, physical and morphological properties. Burning sewage sludge at high temperatures imparts pozzolanic properties to the resulting ash, which, when used as a cement replacement, improves concrete's compressive and tensile strengths. Various SSA replacement levels (5%, 10%, 15%, 20%, and 25%) were tested, with 15% SSA showing the highest strength gains. SSA affects setting time and workability, but treated sewage water does not significantly impact concrete properties. Concrete with SSA showed superior strength compared to conventional mixes with both fresh and treated water. Durability tests revealed that while SSA concrete experienced minor efflorescence in saltwater, it resisted acid attacks better than conventional concrete, indicating its good durability.

On the Growth of Small Cracks in 2024‐T3 and Boeing Space, Intelligence and Weapon Systems AM LPBF Scalmalloy®

ABSTRACTThe desire to use additively manufactured (AM) parts to ensure the availability of military aircraft, and to build limited‐life unmanned aerial vehicles (drones), coupled with the United States Air Force (USAF) approach to the airworthiness certification of AM parts has focused attention on durability analysis/assessment, and hence on the growth of small cracks in AM parts. Previous studies have shown that laser powder fusion built (LPBF) Scalmalloy® has: i) A yield stress and an ultimate strength that are greater than that of AA2024‐T3 and comparable to that of AA7075‐T6; ii) A resistance to crack growth that is better than that of AA7075‐T6 and comparable to that of AA2024‐T3. However, since the ability to predict the durability of a part is essential for its airworthiness certification, the present paper illustrates how to perform a linear elastic fracture mechanics (LEFM)‐based durability assessment of Boeing Space, Intelligence and Weapon System (BSIWS) LPBF Scalmalloy®. The durability study includes specimens with both machined surfaces and surfaces left in the as‐built condition. As a result, it would appear that BISWS AM LPBF Scalmalloy® is an ideal candidate for building limited‐life AM replacement parts for fixed and rotary wing aircraft and drones.

Sustainable quaternary binders made from metallurgical wastes of northeast Mexico: strength, hydration products, and durability.

In this research, four industrial wastes were used for up to 80% as supplementary cementitious materials (SCMs) in cement mortar systems: ground granulated blast furnace slag, electric arc furnace slag, basic oxygen furnace slag, and waste limestone powder. Quaternary cementitious blends were prepared and studied for up to 120days. Workability, compressive strength, durability, microstructures, and sustainability studies were performed and compared with Portland cement references. Results showed that more than 30MPa in compressive strength can be achieved by > 50% replacement with SCMs; only 9% below the reference. Neither H2SO4 nor MgSO4 attacks resulted in critical damages; nevertheless, curing under NaCl solution showed detrimental behavior. C-S-H with a low Ca/Si ratio was identified in the mortars as the main hydration product, possibly intermixed with stratlingite, C-A-S-H and/or hydrotalcite. Environmental impact for the blended cements was determined as the CO2eq. factor from a simple life cycle assessment. The embodied greenhouse gasses varied in 260.2-541.4kg CO2eq./ton of binder depending on the formulation. This was 40-70% less than Portland cement (922.6kg CO2eq./ton). The production of the raw materials dominated the polluting emissions, while freight, grinding, and sieving had little environmental impact.

The attrition, physical and insecticidal durability of two dual active ingredient nets (Interceptor® G2 and Royal Guard®) in Benin, West Africa: results from a durability study embedded in a cluster randomised controlled trial.

Studies evaluating the attrition, physical and insecticidal durability of dual active ingredient (AI) insecticide-treated nets (ITNs) are essential for makingprogrammatic decisions regarding their deployment. We performed a prospective study embedded in a cluster randomised controlled trial (cRCT) to evaluate the attrition, fabric integrity and insecticidal durability of Interceptor® G2 (alpha-cypermethrin-chlorfenapyr) and Royal Guard® (alpha-cypermethrin-pyriproxyfen), compared to Interceptor® (alpha-cypermethrin) in Benin. A total of 2428 study nets in 1093 randomly selected households in five clusters per arm of the cRCT were monitored for ITN attrition and fabric integrity every 6-12months post-distribution. Householders were further surveyed to investigate non-study net use and their preference for ITN fabric types used in the study nets. A second cohort of 120 nets per ITN type were withdrawn every 12months and assessed for chemical content and insecticidal activity in laboratory bioassays. Alpha-cypermethrin bioefficacy was investigated using the susceptible Anopheles gambiae Kisumu strain, and chlorfenapyr and pyriproxyfen bioefficacy were investigated using the pyrethroid-resistant Anopheles coluzzii Akron strain. Net pieces were tested in WHO cone bioassays and tunnel tests for alpha-cypermethrin and in tunnel tests for chlorfenapyr; pyriproxyfen activity was assessed in cone bioassays as the reduction in fertility of blood-fed survivors using ovary dissection. Bioefficacy was expressed as the proportion of ITNs passing predetermined WHO criteria, namely knock-down ≥ 95% or 24/72h mortality ≥ 80% or reduction in fertility ≥ 50%. Overall ITN survivorship was 52% at 24months and fell to 15% at 36months. Median ITN survival time was lower with Royal Guard® relative to Interceptor® [1.6 vs 2.3years; hazard ratio (HR) 1.49, 95% confidence interval (CI) 1.36-1.66; p < 0.001] and Interceptor® G2 (1.6 vs 2.1years; HR 1.33, 95% CI 1.20-1.47; p < 0.001). Householders overwhelmingly preferred polyester nets over polyethylene nets (96%), and more Royal Guard® nets were replaced with spare polyester nets from previous campaigns. All Royal Guard® nets passed efficacy criteria for alpha-cypermethrin at all time points (100%) while ITN pass rates after 24months had fallen to < 40% for pyriproxyfen and chlorfenapyr. The chemical content analysis showed a higher loss rate of the non-pyrethroid insecticides relative to the pyrethroids in each dual ingredient AI ITN; 74% vs 47% for Royal Guard® and 85% vs 63% for Interceptor® G2 at 36months. The median ITN survival time for Interceptor® G2 (2.1years) and Royal Guard® (1.6years) in Benin is substantially lower than 3years. Royal Guard® nets were discarded more quickly by householders, partly due to their low preference for polyethylene nets. The insecticidal activity of the non-pyrethroid insecticides in both dual AI ITNs was short-lived compared to alpha-cypermethrin. The results corroborate the findings from the cRCT conducted in Benin.

Sustainable furfural bis-thymol based benzoxazines: Superhydrophobic, aggregation induced emission and corrosion resistant properties

Sustainable bis-thymol based benzoxazines have been synthesized using furfural bis-thymol (FBT) and paraformaldehyde separately with five different fluorine substituted amines through Mannich condensation process. The molecular structure of the obtained benzoxazines has been verified using spectroscopic analyses. The curing temperature of the synthesized benzoxazines are ranged between 241°C and 277°C. Among the synthesized polybenzoxazines, poly(FBT-pfa) exhibits the highest thermal stability of 52% char yield. All the polybenzoxazines exhibit the value of LOI above the threshold limit of 26 which infers the self-extinguishing property of the polymer. Poly(FBT-pfsa) showed the highest value of water contact angle of 151o, which ascertains that the increased fluorine content contributes to the superhydrophobic nature. Results from hydrophobic durability studies with poly(FBT-pfsa) using coated cotton fabric under acidic and basic conditions indicate its suitability for hydrophobic applications. The corrosion protection ability of polybenzoxazines towards mild steel surfaces was studied and the results obtained suggest that these polybenzoxazines can be used as an excellent coating material. UV-Visible and fluorescence spectroscopic analyses infer that these benzoxazines exhibit aggregation induced emission (AIE) characteristics. Data from different studies suggest that these materials can be conveniently utilized in the form of optical, superhydrophobic and corrosion-resistant coatings.

Material Design and Performance Study of a Porous Sound-Absorbing Sound Barrier

A new type of porous sound-absorbing sound barrier was developed with quartz sand and self-developed polysiloxane resin. The forming process of the material was studied. The test specimens of the porous sound-absorbing sound barrier were prepared with different mesh numbers of quartz sand and different proportions of resin, and the void properties, compressive strength, durability, and acoustic performance were investigated. Based on the mix design results, it is suggested that 20-mesh quartz sand and a 10:1 mass ratio of quartz sand are used to prepare the porous sound-absorbing sound barrier. The durability study showed that the porous sound-absorbing sound-barrier material had good salt and alkali resistance, poor acid resistance, good water stability, and freeze–thaw stability. The laboratory acoustic test and practical engineering application results showed that the porous sound-absorbing sound barrier had excellent acoustic performance and good noise-reduction effects.

INVESTIGATION OF THE INFLUENCE OF CHOOSING THE TYPE OF FACADE SYSTEM USING ABC ANALYSIS ON THE COST OF THE LIFE CYCLE OF THE BUILDING OBJECT

The article is devoted to a comprehensive study of the influence of the choice of the type of facade systems on the total cost of the life cycle of the construction object, with a special emphasis on the application of ABC-analysis as a tool for determining the optimal option for arranging the facade, taking into account economic and quality aspects. The main purpose of the article is to justify the feasibility of using ABC analysis to select the type of facade systems and assess its impact on the costs associated with the life cycle of the building. The article provides a detailed analysis of various types of facade systems from the point of view of their fastening, materials, design and method implementation. Such systems as ventilated and non-ventilated facades, hinged ventilated facade systems, facades with cladding made of natural stone, composite materials and other modern materials are considered. Special attention is paid to the study of technological characteristics, durability and maintenance costs of various types of facade systems. The application of ABC analysis allows classifying facade systems according to their impact on the cost and quality of construction. In this context, facade systems are divided into three categories: A - the most important and expensive, B - medium importance and expensive, C - less important and with minimal expenses. This approach allows builders and designers to focus their attention on the most critical elements that affect the overall cost and efficiency of construction.As a result of the study, it becomes possible to make an informed decision regarding the choice of the optimal facade system, which best meets the specific needs of the project and contributes to the optimization of the cost of the life cycle of the building. In particular, the selection of appropriate materials and technologies allows to reduce construction costs, ensure durability and reduce maintenance and repair costs in the future. In addition, the results of the study can become the basis for the development of practical recommendations for professionals in the construction industry, including builders, designers and architects. This makes it possible to create more efficient, economical and ecologically sustainable construction objects. Also, the article emphasizes the importance of creating specialist training schools and conditions for the successful implementation of life cycle assessment technologies in the construction industry.

Determining pore size distribution in rocks using shear‐thinning fluids: Utilisation of the method in geomorphology

AbstractThe pore space characteristics of geological materials are closely related to their mechanical, transport and hydraulic properties. In geomorphology, pore size distribution (PSD) is an important characteristic in rock weathering, evaporation and other studies. In an effort to find novel methods to determine the PSD, perhaps to bypass the disadvantages of the current techniques, there has been a growing interest in the use of non‐Newtonian fluids. In this contribution, we are particularly interested in the method recently introduced by Abou Najm and Atallah (the ANA method), which exploits the way in which the flow of different shear‐thinning fluids distributes differently in the pore space to compute the functional PSD estimation. We performed a set of saturated flow experiments with aqueous xanthan gum solutions of different concentrations, using as simple as possible laboratory settings, and we implemented a modified version of the previously introduced numerical model to obtain the PSDs of four sandstone and one tuff samples. The results are compared with conventional mercury intrusion porosimetry, showing a good agreement regarding the dominant pore size and a notable similarity in the distributions. Several limitations were identified as well, such as the lack of information on relatively small pores (&lt;5–10 μm for the samples studied) and the potential issues in obtaining a more detailed distribution. We conclude that the ANA method is promising for geomorphological evaporation and rock durability studies, particularly for coarser materials such as sandstone, but it also encounters challenges for certain applications, especially for fine‐grained rocks. It must be acknowledged that the ANA method has been tested on a limited range of materials and further investigation is required to fully explore its capabilities and limitations.

Strength Properties Evaluation of Composite Blocks Incorporated With Acacia Nilotica Ash

&lt;p style="text-align:justify"&gt;&lt;span style="font-size:11pt"&gt;&lt;span style="font-family:&amp;quot;Times New Roman&amp;quot;,&amp;quot;serif&amp;quot;"&gt;&lt;span style="font-size:10.0pt"&gt;Owing to the order of the day, we are searching for an eco-friendly binding ingredient instead of cement, which is now universally used in concrete. Almost everyone extensively exploits construction materials due to their good durability and compressive characteristics. The present study examines the use of acacia nilotica ash as a cement substitute. It is known that acacia nilotica`s aggressive roots are extremely presumptuous and invasive and spoil the foundation of buildings. By gripping water from adjoining areas, they change soil nitrogen and are a major source of affecting plant growth. In this work, the M&lt;sub&gt;35&lt;/sub&gt;-grade geocomposite was investigated by incorporating acacia nilotica ash at 0%, 2.5, 5%, 7.5%, 10%, 12.5%, and 15% for fly ash. Mechanical and durability studies were carried out by changing the magnitude of acacia nilotica ash and evaluating it with the standard composite samples.&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;

Impact of the atmosphere on the sintering capability and chemical durability of Nd-doped UO2+x mixed oxides

In this study, the influence of the working atmosphere on the sinterability and chemical durability of Nd-doped UO2 mixed oxides was investigated. To this end, the starting powder was first prepared by a hydroxide co-precipitation route, resulting in a nano-sized granulometry combined with a high specific surface area. The powders were then converted to oxides by heating and sintered in pellet form at 1600°C under an argon or reducing (Ar-4 %H2) atmosphere. The use of argon or reducing atmosphere resulted in very different densification pathways and final microstructures. The reducing sintering atmosphere hindered the uranium (IV) oxidation that could occur at high temperature, leading to the formation of U3O8, as was the case when working under argon atmosphere. Regarding the microstructure of the sintered pellets, the use of an argon sintering atmosphere resulted in an average grain size ten times larger than that of a reducing sintering atmosphere, while macroscopic properties such as relative density, porosity and homogeneity of cation distribution at the pellet scale remained the same. Nevertheless, a slight local enrichment of Nd at the grain boundaries was observed for the pellet sintered under Ar-4 %H2. In a second step, the study of the chemical durability of these sintered samples showed a significant influence of the sintering atmosphere on the dissolution kinetics and mechanism. These differences could be related to the microstructural properties of the pellets, i.e. the average grain size and the occurrence of grain boundaries. The cation distribution in the pellets could also influence their chemical durability, such as local Nd enrichment, the formation of defects in the oxygen sublattice and the presence of a different fraction of U(V) depending on the sintering atmosphere, as shown by HERFD-XANES measurements. The use of reducing or argon sintering atmospheres could even direct the charge compensation mechanisms that occur into the solid, thereby simultaneously affecting the sinterability and chemical durability of the samples.

Exploring the Role of Coordinating Environments on Durability of Nickel-Based Catalysts for Hydrogen Evolution Reactions

Ni-based platinum-group-metal (PGM)-free catalysts for hydrogen evolution reaction have been considered viable for the commercialization of alkaline exchange membrane water electrolysis (AEMWE) due to their high activity and low cost. Even though several highly active Ni-based catalysts have been developed in recent years, their long-term stability under commercially relevant conditions was not systematically assessed, preventing a direct comparison with the currently used catalysts. While not as active, the current commercial PGM-free catalysts are highly stable, with an operational life measured in decades. However, conducting durability assessments through long-term durability studies can take over 10,000 hours which is impractical. Consequently, accelerated stress tests (ASTs) specifically targeting the catalyst and simulating uncontrolled shutdown and high overpotential scenarios are needed to further improve AEMWE technology.In this presentation, the ASTs of several Ni-based catalysts with different coordination environments (nickel molybdenum, nickel cupferron1, Ni-NiO, and a novel high surface area de-alloyed Ni catalyst) will be explored. The catalysts were subjected to high overpotentials and uncontrolled shutdown cycles in both liquid electrolyte and AEMWE cells. The structure of these catalysts was observed using in situ Raman spectroscopy, XRD, TEM, and BET gas adsorption analysis and correlated to changes in electrochemical performance. The determination of the catalyst structure during these ASTs is paramount in designing durable PGM-free catalysts for improved AEMWE performance.1) Doan, H.; Kendrick, I.; Blanchard, R.; Jia, Q.; Knecht, E.; Freeman, A.; Jankins, T.; Bates, M. K.; Mukerjee, S. Functionalized Embedded Monometallic Nickel Catalysts for Enhanced Hydrogen Evolution: Performance and Stability. J. Electrochem. Soc. 2021, 168 (8), 084501. https://doi.org/10.1149/1945-7111/ac11a1.

The Effect of Water Quality on PEM Electrolyzer Performance

There has been growing interest in the use of removable, clean, and sustainable energy sources as a solution to eliminate environmental problems caused by fossil fuels. In particular, the electrolysis of water to produce green hydrogen is one of the most promising technologies. Among various electrolysis techniques, proton exchange membrane water electrolyzer (PEMWE) stands out as the most promising for mobility and large-scale energy-storage applications (1). Hydrogen production by PEMWEs requires approximately 45 kg of high-quality water to produce 5 kg of hydrogen. It has been estimated that about 22% of the total cost of a state-of-the-art PEMWE system is for water deionization treatment (2). This water purity requirement is not only an economic barrier, but also a constraint for the use of this system in areas where high-quality water is not accessible or in areas where water for human consumption is a scarce resource. Therefore, studying the effect of water quality on PEMWE performance is an important first step in identifying key degradation mechanisms on the path to discovering new PEMWE architectures that are more tolerant of poor-quality feed waters.In this work, the effect of common impurities, such as Na+ and Mg2+, in feed water on the performance of common PEMWE architectures is studied. The main goals of the work are: 1) to understand the tolerance range for long term operation, 2) to identify major degradation mechanisms when the failure occurs. Experiments were carried out in an electrolyzer equipped with platinized Ti electrodes, IrO2 and Pt/C as anodic and cathodic catalysts, respectively, and a 115 Nafion® membrane. Durability studies of 100-hour duration and electrochemical characterization of the electrolyzer at different time intervals (polarization curves and impedance spectroscopy) were performed. The membrane/electrode assembly was probed by SEM /EDX before and after the experiments and cation concentrations in the water were monitored by ICP. An electrochemical model is proposed to explain the observed behavior of the electrolyzer with DI water and in the presence of impurities.The results show that the presence of cations affects the performance of the electrolyzer at different levels depending on the concentration of the cation and its valence (Mg2+ > Na+ >DI water). Mg+2 had the same effect as Na+ even at 5 times lower concentration. Cations have higher affinity than protons for sulfonic acid groups (-SO3 -), leading to a displacement of protons and a consequent reduction in the membrane proton conductivity. However. according to the polarization curves, there are effects beyond the ohmic potential due to the increase in membrane resistance. The major effect of cations is on the reaction kinetics, which is the primary reason for the observed increase in cell voltage. The presence of cations within the membrane blocks the transport of protons, which creates a lack of protons at the cathode, resulting in the kinetic change from proton reduction to reduction of water. Moreover, the EDX results showed that Na+ and Mg2+ ions transfer from anode to cathode and deposit on the membrane and catalyst layers, which may cover the active catalyst sites, block the proton transport inside the membrane and degrade the catalyst ionomer layers.References Sazali N. Emerging technologies by hydrogen: A review. International Journal of Hydrogen Energy. 2020 (45): 18753-18771Becker H, Murawski J, Shinde DV, Stephens IEL, Hinds G, Smith G. Impact of impurities on water electrolysis: A review. Sustainable Energy & Fuels. 2023;7(7):1565-603.

(Invited) Integrated Approach of Modeling, X-Ray and Electrochemical Characterization to Understand Low Iridium Loading Catalyst Layers Integration and Durability

Proton exchange membrane water electrolyzers (PEMWEs) will share more than 40 % of green hydrogen production market by 2050. Currently, iridium catalyst in the anode catalyst layers amounts to 1 mg/cm2. To enable low-loading (0.4 mg/cm2) or ultra-low loading (<0.1 mg/cm2) designs we need to better understand both integration of catalysts into catalyst layer and their durability. At low loadings catalyst layer in-plane electric conductivity can be compromised, requiring either supported catalyst layers or the need for microporous layer (MPL) design. For durability study it is necessary to understand the pathway of surface of IrOx transformation during accelerated stress tests (ASTs) and identify optimal beginning of life (BOL) structure for long-duration deployment. In this work we evaluate the structure and performance of amorphous and crystalline IrOx catalysts at the BOL and EOL to build structure-to-property relations. Rheology studies are conducted to identify the optimal ink recipe for each of the catalysts for blade coating deposition method. We use operando x-ray diffraction technique to evaluate catalyst structure evolution during AST cycling. X-ray computed tomography (CT) was used to evaluate catalyst layer – MPL interfaces under various operando conditions. The morphological information was integrated into the two-dimensional model to better understand interfaces for the low-loading PEMWEs.

Durability Studies and Stress Strain Characteristics of hooked end steel fiber reinforced ambient cured geopolymer concrete

Abstract For conventional concrete, the use of fibers has proven to improve the strength properties of the material. However, in the case of ambient cured geopolymer concrete, there are limited studies that explore the application of fibers, in particular, the use of hooked end steel fibers. Further, it is important to study the durability properties of geopolymer concrete with fibers, since it will influence the service life of the structures in practice. Therefore, in the present study, fiber-reinforced geopolymer concrete was synthesized using fly ash, GGBS, hooked end steel fibers, and alkaline solution made with Na2SiO3 and NaOH. The percentage of steel fibers varied in the range of 0.5% to 2% with an increment of 0.5% by volume fraction of the binder. The precursor materials were characterized using techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscope (SEM). Durability studies like water absorption, drying shrinkage, sulphate attack were studied. In addition, the elastic constants were determined through stress strain behaviour of geopolymer concrete in uniaxial compression. The results of the experimental study showed that the addition of hooked end steel fibers influences the strength of geopolymer concrete up to an optimal percentage, which was found to be 1%. Furthermore, in terms of durability properties, the addition of fibers exhibited better results in terms of resistance to water absorption and chemical attack, and this was validated by the microstructural studies, where the specimens with hooked end steel fibers revealed much denser hardened geopolymer matrix when compared to the mixes without fibers.