Showing papers on "Durability published in 2020"

Durable Cathodes and Electrolyzers for the Efficient Aqueous Electrochemical Reduction of CO2

Abstract: The world emits over 14 gigatons of CO2 in excess of what can be remediated by natural processes annually, contributing to rising atmospheric CO2 levels and increasing global temperatures. The electrochemical reduction of CO2 (CO2 RR) to value-added chemicals and fuels has been proposed as a method for reusing these excess anthropogenic emissions. While state-of-the-art CO2 RR systems exhibit high current densities and faradaic efficiencies, research on long-term electrode durability, necessary for this technology to be implemented commercially, is lacking. Previous reviews have focused mainly on the CO2 electrolyzer performance without considering durability. In this Review, the need for research into high-performing and durable CO2 RR systems is stressed by summarizing the state-of-the-art with respect to durability. Various failure modes observed are also reported and a protocol for standard durability testing of CO2 RR systems is proposed.

Pultruded materials and structures: A review:

Abstract: Currently, the application of pultruded profiles is increasing owing to their advantages, such as light weight, high strength, improved durability, corrosion resistance, ease of transportation, spe...

Enveloping SiOx in N-doped carbon for durable lithium storage via an eco-friendly solvent-free approach

Abstract: Silicon oxides, SiOx, have aroused significant interests as high-capacity lithium-ion battery anode materials To address the conductivity and volume fluctuation issues of SiOx for practical applications, herein, we develop a novel eco-friendly, solvent-free, flammable gas-free approach to envelop SiOx submicron particles in N-doped carbon (denoted as SiOx@NC) The carbon encapsulation not only improves the electrical conductivity but also buffers the volume variation of SiOx, resulting in boosted lithium storage performances Specifically, the as-prepared SiOx@NC affords high reversible capacity (774 mA h g−1), ideal rate capability, and long-term durability (112% capacity retention over 500 cycles) It is expected that the solvent-free, flammable gas-free method we developed here can be generally applied to other high-capacity anode materials, such as Si, Sn, and Sb

Utilization of industrial and agricultural wastes for productions of sustainable roller compacted concrete pavement mixes containing reclaimed asphalt pavement aggregates

Abstract: Asphalt pavement recycling has become a common practice across the globe and has been successfully employed in construction of new pavements. While several studies considered utilization of reclaimed asphalt pavement (RAP) aggregates for flexible and rigid pavements, very few attempted its possibility for roller compacted concrete pavements (RCCP). Additionally, studies on the possibility of enhancing the proportion of RAP for RCCP are very scanty. The present study is an attempt to increase the potential of RCCP mixes containing 50% RAP (dust contaminated & stiffened asphalt coated: 50RAP via including various industrial and agricultural wastes such as Silica Fume, Fly ash, and Sugarcane ash as partial replacement of conventional cement. It was observed that the inclusion of the stated admixtures had an insignificant effect on the density of the fresh RCCP mixes, however, increased the moisture demand considerably. In fact, the results firmly indicated the potential of silica fume for RAP-RCCP blends, as, it not only enhanced the physical and mechanical properties, but found to improve the durability of RCCP mixes considerably. Also, utilization of silica fume was found to be economical & environmentally friendly amongst all wastes: with reduced initial construction cost & CO2 emissions by up to 8.4% & 9.7%. As far as the other industrial wastes are concerned, 15% fly ash could also be utilized for producing sustainable RCCP mixes, whereas, higher dosage of fly ash (30%) and sugarcane ash (10 & 15%) may be employed as base layer material of conventional concrete pavements.

Review on Mechanical Thermal Properties of Superalloys and Thermal Barrier Coating Used in Gas Turbines

Abstract: This paper describes the manufacturing method and properties of a superalloy as a gas turbine blade material and a thermal barrier coating to protect it. The development process of superalloy and characteristics of each casting method were introduced. In particular, the single crystal superalloys were analyzed for creep and tensile properties with temperature according to chemical composition. In addition, the theories of creep life prediction models were summarized and comparative analysis was performed. Finally, the manufacturing processes of thermal barrier coatings were introduced, and the characteristics and effects of mechanical, thermal, and durability characteristics of each manufacturing process are described. We believe that this comprehensive review will help not only the gas turbine industry/community, but also material scientists, measurement physicists/engineers, and theorists interested in superalloys and high-temperature ceramics.

Early-age behaviour and cracking potential of fly ash concrete under restrained condition

Abstract: High-performance concrete (HPC) has been used extensively due to its good workability, lasting durability and high strength. However, the low water/cement ratio in HPC generally induces rather high...

Effect of Fibers on Durability of Concrete: A Practical Review.

Abstract: This article reviews the literature related to the performance of fiber reinforced concrete (FRC) in the context of the durability of concrete infrastructures. The durability of a concrete infrastructure is defined by its ability to sustain reliable levels of serviceability and structural integrity in environmental exposure which may be harsh without any major need for repair intervention throughout the design service life. Conventional concrete has relatively low tensile capacity and ductility, and thus is susceptible to cracking. Cracks are considered to be pathways for gases, liquids, and deleterious solutes entering the concrete, which lead to the early onset of deterioration processes in the concrete or reinforcing steel. Chloride aqueous solution may reach the embedded steel quickly after cracked regions are exposed to de-icing salt or spray in coastal regions, which de-passivates the protective film, whereby corrosion initiation occurs decades earlier than when chlorides would have to gradually ingress uncracked concrete covering the steel in the absence of cracks. Appropriate inclusion of steel or non-metallic fibers has been proven to increase both the tensile capacity and ductility of FRC. Many researchers have investigated durability enhancement by use of FRC. This paper reviews substantial evidence that the improved tensile characteristics of FRC used to construct infrastructure, improve its durability through mainly the fiber bridging and control of cracks. The evidence is based on both reported laboratory investigations under controlled conditions and the monitored performance of actual infrastructure constructed of FRC. The paper aims to help design engineers towards considering the use of FRC in real-life concrete infrastructures appropriately and more confidently.

Assessment of geopolymer composites durability at one year age

Abstract: Geopolymers are important alternative materials for use in support of recycling and sustainability, and one of the most important properties is durability. While many studies perform durability tests 28 days after production, we carried out durability tests on a mixture of geopolymers starting 365 days after production. In this case, other conditions that occur until durability conditions are applied are taken into consideration. The geopolymer mixture consisted of metakaolin (90% by wt.) and boron waste colemanite (10% by wt.). The study investigated heat and wet-dry curing methods and polyolefin and polyamide fibre ratios (0.5, 1.0, and 1.5% by vol.) on durability. Durability issues related to concrete, such as long-term exposure to hydrochloric acid, freeze-thaw cycles, and abrasion were recorded. Results show that polyamide fibres provide better results than polyolefin fibres, the optimum polyamide fibre ratio was 1%, and the wet-dry curing method increased geopolymerisation more than heat curing. The Si-O-Al bonds were found to be stronger after wet-dry curing. All durability studies showed that the compact structure of the geopolymers withstood the durability tests performed one year after production. Scanning electron microscopy (SEM) analysis supports these results.

Mulberry paper-based graphene strain sensor for wearable electronics with high mechanical strength

Abstract: Paper-based electronics is an emerging technology that is attracting attention for its high flexibility, ease of recycling/disposal, low manufacturing cost, and scalability. In this work, graphene flakes dispersion was coated on the mulberry papers through a simple Meyer-rod coating process. The characteristics of the mulberry paper-based graphene strain sensor (MPGSS) were systematically researched by investigating the electrical performance with strain, mechanical strength, flexibility, environmental stability, and degradability of the as-fabricated strain sensor. As a result, MPGSS exhibited suitable coating processability, a mechanical resistance of 1.13 MPa, a gauge factor of 3.82, durability over 1000 cycles of bending testing, and high scalability. In addition, its higher tear strength and degradability in nature was investigated in comparison with that of copy paper. Overall, the coated graphene sensor reinforced with mulberry paper holds great potential for next-generation wearable applications.

Durability of concrete containing recycled concrete coarse and fine aggregates and milled waste glass in magnesium sulfate environment

Abstract: Globally very large amounts of natural resources are being consumed every year due to the rapid growth of the demand for concrete in the construction industry. To address this problem recycling of demolished concrete has been introduced as a rational and practical solution for dealing with construction waste. In parallel to this, the use recycled materials in concrete, such as milled waste glass (MWG), has been widely examined with the aim of improving concrete strength and durability. In this study, the durability of concrete mixes containing recycled coarse aggregate (RCA) and recycled fine aggregate (RFA) as partial replacement (0% and 30%) of aggregates (gravel and sand), and MWG as partial replacement (0% and 30%) of cement was investigated. Concrete cubes were subjected to saturated magnesium sulfate solution, and the concrete durability was examined through a set of indicator parameters, including the expansion, mass variation, water absorption, and compressive strength of the concrete samples. A durability loss index (DLI) was introduced based on the aforementioned parameters to evaluate the durability of concretes in different groups. The results show that expansion and water absorption of concrete exposed to sulfate environment decreased with using RFA in the concrete mix by 17% and 26%, respectively, compared to conventional concrete. Also, the compressive strength results of sulfate-exposed specimens illustrate that simultaneous use of MWG with RCA and RFA can increase the sulfate durability of concrete in term of the compressive strength by 15% and 53%, respectively. In addition, DLI of mixes indicates that durability of concrete containing RCA, RFA and MWG may not be influenced much by the exposure of concrete to sulfate environment relative to normal concrete if appropriate mix proportions are adopted.

Durability Properties of Alkali Activated Slag Composites: Short Overview

Abstract: Despite the advances in studies utilizing industrial, construction and agricultural wastes as alternative materials for concrete making, there are still gaps to be covered on the durability characteristics of most materials. This study presents a shot overview on the durability properties of alkali-activated slag (AAS) composites. The durability properties of AAS explored include permeability, alkali silica reaction, carbonation, freeze and thaw, fire resistance, corrosion, and resistance to sulphate, chloride and acid attacks. The research outcomes indicated that AAS possessed strong durability characteristics in terms of resistance to acid and sulphate attacks, however, areas such as permeability, alkali silica reaction, carbonation and freeze-thaw resistance, have not been overly explored. A general overview of the performance and limitations of AAS has been provided, and the study suggested specific areas for further investigations. The information provided in this study will be useful for users of AAS, and pave way for innovative researches on AAS composite.

Effects of environmental actions, recycled aggregate quality and modification treatments on durability performance of recycled concrete

Abstract: The durability performance of recycled concrete (RC) subjected to different environmental actions, including salt-solution, mechanical load, salt-solution freeze-thaw cycles, and coupled mechanical load and salt-solution freeze-thaw cycles was investigated in this paper. To evaluate the effects of recycled aggregate (RA) quality on the RC durability, modeled recycled concrete (MRC) containing modeled recycled aggregate (MRA) with various thickness and coverage of old mortar, along with different degrees of initial damage, was fabricated and tested. Moreover, several modification treatments were employed to study the effects of modification treatments on the RC durability, which included the impregnation of RA with polyvinyl alcohol (PVA) emulsion or nano-SiO2 solutions, and the enhancement of RC with the incorporations of fly ash or hybrid fly ash and silica fume. The results reveal that the deterioration of RC under coupled actions of mechanical load and salt-solution freeze-thaw cycles was the most severe, which was followed by the salt-solution freeze-thaw cycles, mechanical load and salt-solution. The old interface in RA was determined as the weakest zone in RC. With the increase in the thickness or coverage of old mortar, or the initial damage of RA, the durability performance of RC declined, and the effect of initial damage of RA was more significant compared to the thickness or coverage of old mortar. Additionally, modifying RC with 1.5% nano-SiO2 solution or PVA emulsion, and replacing cement with 10% fly ash can significantly enhance the RC durability.

A Study on Mechanical and Durability Aspects of Concrete Modified with Steel Fibers (SFs)

Abstract: Concrete is weak in tension and strong in compression which results in brittle failure. This is obviously unacceptable for any construction materials. Thus, concrete requires some type of tensile reinforcement to balance its brittle behavior and improves its tensile strength. Adding of fibers is one of the most prevalent techniques to enhance the tensile behavior of concrete. Fiber slows cracking phenomena and increases energy absorption capacity of the structure. Majority researchers focus on mechanical performance of fiber reinforced concrete. In this research, the influence of various dosages of steel fibers (0%, 1.0%, 2.0%, 3.0%, and 4.0% by weight of cement) is investigated on the mechanical and durability properties of concrete. Mechanical properties such as compressive strength and split tensile strength are studied at 7- and 28-days curing. To evaluate the durability aspects of each mix, various parameters such as water absorption, acid attack resistance, and permeability are investigated. Results indicate that strength was increased up to 2% addition of steel fiber and then reduced gradually. It also indicates that, durability parameter of concrete for example water absorption, permeability, and acid attack resistance considerably improved with incorporation of steel fibers at 2.0% incorporation of steel fibers. Therefore, it is recommended to mix steel fibers up 2.0% by weight of cement to achieved maximum benefits.