Influence of Recycled Concrete Fine Powder on Durability of Cement Mortar

In this paper,the durability of cement mortar prepared with a recycled-concrete fine powder(RFP)was examined;including the analysis of a variety of aspects,such as the carbonization,sulfate attack and chloride ion erosion resistance.The results indicate that the influence of RFP on these three aspects is different.The carbonization depth after 30 days and the chloride diffusion coefficient of mortar containing 10%RFP decreased by 13.3%and 28.19%.With a further increase in the RFP content,interconnected pores formed between the RFP particles,leading to an acceleration of the penetration rate of CO_(2)and Cl^(−).When the RFP content was less than 50%,the corrosion resistance coefficient of the compressive strength of the mortar was 0.84-1.05 after 90 days of sulfate attack.But the expansion and cracking of the mortar was effectively alleviated due to decrease of the gypsum production.Scanning electron microscope(SEM)analysis has confirmed that 10%RFP contributes to the formation of a dense microstructure in the cement mortar.

Durability evaluation for existing railway engineering: a review

Purpose – This study aims to analyze the factors, evaluation techniques of the durability of existing railwayengineering.Design/methodology/approach – China has built a railway network of over 150,000 km. Ensuring thesafety of the existing railway engineering is of great significance for maintaining normal railway operationorder. However, railway engineering is a strip structure that crosses multiple complex environments. Andrailway engineering will withstand high-frequency impact loads from trains. The above factors have led todifferences in the deterioration characteristics and maintenance strategies of railway engineering compared toconventional concrete structures. Therefore, it is very important to analyze the key factors that affect thedurability of railway structures and propose technologies for durability evaluation.Findings – The factors that affect the durability and reliability of railway engineering are mainly divided intothree categories: material factors, environmental factors and load factors. Among them, material factors alsoinclude influencing factors, such as raw materials, mix proportions and so on. Environmental factors varydepending on the service environment of railway engineering, and the durability and deterioration of concretehave different failure mechanisms. Load factors include static load and train dynamic load. The on-site rapiddetection methods for five common diseases in railway engineering are also proposed in this paper. Thesemethods can quickly evaluate the durability of existing railway engineering concrete.Originality/value – The research can provide some new evaluation techniques and methods for thedurability of existing railway engineering.

Influence of railway wheel tread damage on wheel-rail impact loads and the durability of wheelsets

Dynamic wheel-rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds.Based on laser scanning,the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle-track interaction to calibrate and verify a simulation model.The relation between the magnitude of the impact load and various operational parameters,such as vehicle speed,lateral position of wheel-rail contact,track stiffness and position of impact within a sleeper bay,is investigated.The calibrated model is later employed in simulations featuring other forms of tread damage;their effects on impact load and subsequent fatigue impact on bearings,wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed.The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear,and for general assessment of the severity of different types of railway wheel tread damage.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part Two: Durability

This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na2CO3): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.

Lightweight Design of Commercial Vehicle Cab Based on Fatigue Durability

To better improve the lightweight and fatigue durability performance of the tractor cab,a multi-objective lightweight design of the cab was carried out in this study.First,the finite element model of the cab with counterweight loading was established and then confirmed by the physical testing,and use the inertial reliefmethod to obtain stress distribution under unit load.The cab-frame rigid-flexible couplingmulti-body dynamicsmodelwas built by Adams/car software.Taking the cab airbag mount displacement and acceleration signals acquired on the proving ground as the desired signals and obtaining the fatigue analysis load spectrum through Femfat-Lab virtual iteration.The fatigue simulation analysis is performed in nCode based on the Miner linear fatigue cumulative damage theory.Then,with themass and fatigue damage values as the optimization objectives,the bending-torsional stiffness and first-order bending-torsional mode as constraints,the thickness variables are screed based on the sensitivity analysis.The experimental design was carried out using the Optimal Latin hypercube method,and the multi-objective optimal design of the cab was carried out using theKriging approximationmodel fitting and particle swarmalgorithm.The weight of the optimized cab is reduced by 7.8%on the basis of meeting the fatigue durability performance.Finally,a seven-axis road simulation test rig was designed to verify its fatigue durability.The results show the optimized cab can consider both lightweight and durability.

Graphene quantum dots as sulfiphilic and lithiophilic mediator toward high stability and durable life lithium-sulfur batteries

The development of lithium-sulfur(Li-S) battery as one of the most attractive energy storage systems among lithium metal batteries is seriously hindered by low sulfur utilization, poor cycle stability and uneven redeposition of Li anode. It is necessary to propose strategies to address the problems as well as improve the electrochemical performance. One of the effective solutions is to improve the sulfiphilicity of sulfur cathode and the lithiophilicity of the Li anode. Herein, we reported that a synergistic functional separator(graphene quantum dots(GQDs)-polyacrylonitrile(PAN) @polypropylene(PP) separator)improved the electrochemical activity of sulfur cathode as well as the stability of Li anode. GQDs induced uniform Li^(+)nucleation and deposition, which slowed down the passivation of Li anode and avoided shortcircuit. Further, three-dimensional network constructed by electrospinning nanofibers and the polar functional groups of GQDs could both effectively inhibit the shuttle of LiPSs and improve the sulfur utilization. The stability of Li-S battery was improved by the synergistic effect. In addition, GQDs and electrospinning nanofibers protector increased lifetime of separators. Benefiting from the unique design strategy, Li//Li symmetric battery with GQDs-PAN@PP separators exhibited stably cycling for over 600 h. More importantly, the Li-S full batteries based GQDs-PAN@PP separators enabled high stability and desirable sulfur electrochemistry, including high reversibility of 558.09 mA h g^(-1)for 200 cycles and durable life with a low fading rate of 0.075% per cycle after 500 cycles at 0.5 C. Moreover, an impressive areal capacity of 3.23 mA h cm^(-2)was maintained under high sulfur loading of 5.10 mg cm^(-2). This work provides a new insight for modification separator to improve the electrochemical performance of Li-S/Li metal batteries.

A Review of the Advances Made in Improving the Durability of Welded Wood against Water in Light of the Results of African Tropical Woods Welding

Wood plays a major role in the production of furniture and wooden structures.Nevertheless,in this process,the massive use of adhesives and plural connectors remains a definite problem for health and the environment.Therefore,wood welding is a breakthrough in this respect.This paper reviews the applications of wood welding in furniture and construction and then examines advances in improving the durability of welded wood against water.Our contribution also highlights the need to join African tropical woods using the rotational friction welding technique.According to our results,these woods present interesting chemical singularities,which could provide solutions to the water vulnerability of the welded wood.Moreover,the use of such a joining method would first free the Cameroonian furniture industry from the chemical industry,secondly position it at the forefront of new eco-design trends and thirdly make it competitive with other countries in the Central African sub-region.These works enrich the long and rich bibliography on the technique of wood welding,which has long been conspicuous by its absence of tropical woods.

Mechanical Properties and Durability of Sustainable Concrete Manufactured Using Ceramic Waste:A Review

Green and sustainable concrete has attracted significant attention from the construction industry and researchers since it was proposed.The ceramic waste materials are often directly buried in the ground or placed in an open dump,and the accumulation of ceramic waste contributes to environmental pollution,which makes the recycling of ceramic waste quite urgent.Owing to the pozzolanic activity,excellent mechanical properties and durability,industrial ceramic waste is considered as a suitable substitute for cement or natural aggregates to fabricate renewable concrete.In this paper,the pozzolanic activity of ceramic waste and the workability,mechanical performance,and durability of ceramic concrete are discussed.In addition,the most recent research results pertaining to ceramic concrete are reviewed.Ground ceramic powder improves the workability,compressive strength,resistance to chloride penetration,and carbonation resistance of concrete to a certain extent.Concrete containing ceramic as the aggregate has a lower mechanical performance than ordinary concrete.However,the resistance to chloride penetration,freeze-thaw resistance,and high-temperature resistance of ceramic concrete are remarkable.Ceramic concrete is environmentally friendly,requires fewer energy resources to manufacture than ordinary concrete,and has excellent engineering properties.However,further research is required for future engineering applications.

Facile fabrication of durable superhydrophobic fabrics by silicon polyurethane membrane for oil/water separation

Nowadays, oil contamination has become a major reason for water pollution, and presents a global environmental challenge. Although many efforts have been devoted to the fabrication of oil/water separation materials, their practical applications are still hindered by their weak durability, poor chemical tolerance,environmental resistance, and potential negative impact on health and the environment. To overcome these drawbacks, this work offers a facile method to fabricate the eco-friendly and durable oil/water separation membrane fabrics by alkaline hydrolysis and silicon polyurethane coating. The X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy results demonstrate that silicon polyurethane membrane could be coated onto the surface of hydrolyzed polyester fabric and form a micro-/nano-scaled hierarchical structure. Based on this, the modified fabric could have a stable superhydrophobic property with a water contact angle higher than 150°, even after repeated washing and mechanical abrasion 800 times, as well as chemical corrosion. Moreover, the modified fabrics show excellent oil/water separation efficiency of up to 99% for various types of oil–water mixture. Therefore, this durable, eco-friendly and cost-efficient superhydrophobic fabric has great potential in large-scale oil/water separation.

Workability and Durability of Concrete Incorporating Waste Tire Rubber:A Review

Environmental problems caused by waste tires are becoming increasingly prominent.There is an urgent need to find a green way to dispose of waste tires,and scholars have made considerable efforts in this regard.In the construction industry,rubber extracted from waste tires can be added to concrete to alleviate environmental problems to a certain extent.As a new building material,rubber concrete has superior properties compared to ordinary concrete and has been widely used in many fields.Numerous studies have been conducted worldwide to investigate the effect of waste tire rubber on the performance of concrete.It has been reported that the addition of waste tire rubber has a significant influence on the performance of concrete.Workability influences the hardened performance of rubber concrete,especially the durability.Based on the current research results,the workability and durability of concrete manufactured with waste tire rubber,including water absorption and permeability,carbonation resistance,chloride ion permeability resistance,and freeze-thaw resistance,are summarized in this paper.It is concluded that the addition of waste tires has a negative effect on the workability of concrete.In terms of durability,concrete exhibits better chloride ion penetration resistance and frost resistance,with a higher water absorption rate,and lower anti-permeability and carbonation resistance owing to the addition of waste tire rubber.

Time-varying seismic fragility analysis of durability damage of high-tensile reinforcement ECC bridge pier

The deterioration of the performance of offshore bridges is particularly prominent due to the complex natural environment,including the coupling effects of earthquake and seawater erosion.In particular,bridge piers are the main energy-consuming and load-bearing components,so that excellent seismic capacity of bridge piers is the key to avoiding bridge damage.Although earthquake resistant behavior of ordinary reinforced concrete bridge piers(ordinary pier)can be improved by increasing the section size and reinforcement ratio of piers,the improvement of the earthquake resistant behavior is limited.To further improve the earthquake resistant behavior of bridge piers,high-tensile reinforcement engineered cementitious composite(ECC)bridge piers are utilized and time-varying seismic fragility analysis are conducted in this study.The refined model of a bridge pier is built by OpenSees.First,the influence of ECC replacement height on pier curvature is analyzed to determine the reasonable ECC height.Then,the time-varying fragility analysis of high-tensile reinforcement ECC piers(ECC composite piers)with durability damage are evaluated considering the time-varying law of materials.Four damage states,slight damage,moderate damage,extensive damage and complete collapse,are utilized in the study.These fragility curves indicate the durability damage can debase the earthquake resistant behavior of piers continually,the exceedance probability of the same state of destruction increases with the increase of peak ground acceleration(PGA)and service time of pier.The results also indicate that the corrosion level of chloride ion to pier is small during the early service period,and the bridge pier vulnerable curve is similar to that of the new bridge pier.As the level of chlorine ion corrosion deepens,transcendental probability is increased.Compared with the ordinary pier,the exceedance probability in each limit state of ECC composite piers is significantly reduced.The proposed ECC composite pies leads to better realistic time-varying earthquake resistant behavior.

Ti-Fe_(2)O_(3)/Ni(OH)_(x) as an efficient and durable photoanode for the photoelectrochemical catalysis of PET plastic to formic acid

Photoelectrochemical(PEC) technology provides a promising prospect for the transformation of polyethylene terephthalate(PET) plastic wastes to produce value-added chemicals.The PEC catalytic systems with high activity,selectivity and long-term durability are required for the future up-scaling industrial applications.Herein,we employed the interfacial modification strategy to develop an efficient and stable photoanode and evaluated its PEC activity for ethylene glycol(EG,derived from PET hydrolysate) oxidation to formic acid.The interfacial modification between Fe_(2)O_(3)semiconductor and Ni(OH)xcocatalyst with ultrathin TiO_(x) interlayer not only improved the photocurrent density by accelerating the kinetics of photogenerated charge carriers,but also kept the high Faradaic efficiency(over 95% in 30 h) towards the value-added formic acid product.This work proposes an effective method to promote the PEC activity and enhance the long-term stability of photoelectrodes for upcycling PET plastic wastes.

Modification of Wood by Tannin-Furfuryl Alcohol Resins-Effect on Dimensional Stability,Mechanical Properties and Decay Durability

Furfurylation is a well-known wood modification technology.This paper studied the effect of tannin addition on the wood furfurylation.Three kinds of dicarboxylic acids,adipic acid,succinic acid,and tartaric acid,as well as glyoxal as a comparing agent,were used to catalyse the polymerisation of furanic or tannin-furanic solutions during wood modification.Impregnation of furanic or tannin-furanic solution at a certain concentration into the wood followed with curing at 103℃for a specific duration was performed for the wood modification.Different properties of the modified woods like dimensional stability,resistance of treatment to leaching,mechanical properties,decay durability against white-rot(Coriolus versicolor,Pycnoporus sanguineus)and brown-rot(Coniophora puteana)as well as their chemical and anatomical characteristics were evaluated.Results revealed that the partial substitution of FA by the tannins improved the fixation of the chemicals impregnated in wood.Further,dimensional stability,leaching resistance,Brinell hardness,modulus of elasticity/modulus of rupture,and decay durability properties of the furfurylated wood were also improved in the presence of tannins.Scanning electron microscopy revealed the deposition of the polymer in the wood lumen cells and in the wood cell walls.

Evaluation of the Relationship between Bacteria Concentration and the Strength and Durability of Self-compacting Concrete Incorporating Sporosarcina pasteurii

This research was carried out to evaluate the relationship between the incorporation of calcite precipitation bacteria,sporosarcina pasteurii using calcium lactate as nutrient source and the properties of calcined clay and limestone powder blended self-compacting concrete.Ten mixes were designed and designated S0 to S9 with S0 the control(without bacteria and nutrient)and S1 to S9 at varying bacteria and calcium lactate concentrations and the effect of the bacteria cell density and calcium lactate concentration on the compressive strength,sorptivity and tensile strength with age were evaluated using experimental program and statistical packages(ANOVA and post hoc tests).The result of both the experimental program and statistical evaluation shows that the incorporation of sporosarcina pasteurii and calcium lactate as nutrients had a positive impact on the properties of the ternary blended self-compacting concrete.

西北条锈菌源区冬小麦育种抗条锈病基因的利用现状与策略

【目的】了解中国小麦条锈病西北重要越夏菌源区甘肃陇东和陇南近20年育成小麦品种(系)中抗条锈病基因的利用情况,为陇南小麦条锈病遗传多样性控制,持久抗病品种的培育和可持续绿色健康生态农业奠定基础。【方法】于2019—2020年和2020—2021年种植季对117份冬小麦品种(系)甘肃清水县和四川郫都区进行成株期抗条锈病鉴定,2021年分别用条锈菌CYR33和CYR34对117份品种(系)进行苗期抗条锈病鉴定,并利用分子标记对15个抗条锈病基因进行检测。【结果】田间成株期对条锈菌主要流行致病性混合小种抗病的品种(系)占29.1%,其中,25.6%为陇南区域品种(系),3.4%为陇东区域品种(系),另有25.6%陇南区域感病品种(系)表现慢病性(严重度<20%)。有70.1%品种(系)苗期对CYR33表现抗病,其中,57.3%为陇南区域品种(系),12.8%为陇东区域品种(系);仅6.0%品种(系)苗期对CYR34具有抗病性,为陇南区域的兰天131等7个品种(系)。苗期和成株期抗病品种(系)以2010年后育成的兰天、中梁、天选、兰航选系列品种为主。分子标记检测结合系谱分析,发现抗条锈病基因Yr9、Yr10、Yr17、Yr18、Yr26、Yr28、Yr29、Yr30、Yr41、Yr46、YrZH22和YrZH84在所有检测品种(系)中的频率分别为49.6%、1.7%、12.8%、7.7%、12.8%、20.5%、10.3%、34.2%、2.6%、16.2%、15.4%和27.4%,且多以基因聚合体形式存在于品种(系)中,62.4%品种(系)中聚合了2—5个抗条锈病基因,YrZH84、YrZH22和Yr17中的一个或多个基因与其他抗条锈病基因聚合后,品种(系)的条锈病抗性明显高于其他基因组合。此外,在陇南菌源区,以种植小麦为主的山旱地区域(条锈菌越夏区)所推广的品种(系)中,含有Yr10、Yr17、Yr18、Yr28、Yr29、Yr30、Yr41和Yr46的频率较高,越冬区(川水地)推广品种(系)中主要有Yr26、Yr30、YrZH22和YrZH84,越夏区和越冬区品种(系)的抗性遗传背景差异明显,且越夏区品种(系)含有的抗病基因类型多样性高于越冬区。【结论】在越夏菌源区甘肃陇南、陇东的品种(系)中,抗条锈病基因分布频率、抗病基因类型及数量均有明显提高,避免了品种抗病遗传背景单一化问题,实现了品种(系)中的抗病基因较为复杂多样,部分品种的抗病性保持时间长,表明陇南地区利用小麦品种遗传多样性控制条锈病策略的实施已初显成效。

海砂超高性能混凝土试验

采用未淡化的海砂制备超高性能混凝土(UHPC)和普通混凝土,研究了不同氯离子含量的海砂对UHPC抗压强度、孔结构、快速氯离子渗透性以及内置钢筋耐久性的影响,并与普通混凝土进行分析比较。结果表明,海砂中的氯离子含量对UHPC抗压强度并不会产生较大的消极影响;海砂UHPC的临界孔半径约为2 nm,与海砂普通混凝土不同,孔隙率随海砂中氯含量的增加而增加;即使海砂氯离子含量高达0.636%,海砂UHPC的氯离子渗透性仍可忽略不计;海砂UHPC中钢筋在28 d后处于钝化状态并趋于稳定。

溶胶-凝胶法制备SiO_(2)减反射薄膜及其耐久性

目的增加太阳光在太阳能电池玻璃盖板的透过率,以期提高太阳能电池的转换效率。方法以正硅酸乙酯为原料、乙醇为溶剂、氨水为催化剂,采用碱催化溶胶-凝胶浸渍提拉法,在玻璃表面制备了SiO_(2)减反射薄膜,研究了溶胶中正硅酸乙酯与乙醇物质的量比和提拉镀膜速度对SiO_(2)薄膜光学性质的影响,分析了减反射薄膜的耐久性。结果碱性溶胶制备的SiO_(2)为非晶相,采用浸渍提拉法在玻璃表面制备的薄膜结构疏松,且存在微裂纹。采用正硅酸乙酯与乙醇物质的量比为1∶20、提拉速度为500μm/s及正硅酸乙酯与乙醇物质的量比为1∶30、提拉速度为1000μm/s制备的SiO_(2)薄膜,折射率分别为1.35和1.33,厚度分别为101.11、102.63nm,最大透过率分别高于未镀膜玻璃6.57%和6.94%,在400~1100nm波长范围内的平均透过率分别高于未镀膜玻璃5.01%和5.34%,表明该薄膜具有优异的减反射性能。玻璃表面制备SiO_(2)薄膜后,水接触角约为5°,具有超亲水性。将未镀膜玻璃及镀膜样品在实验室放置5个月后,采用正硅酸乙酯与乙醇物质的量比为1∶20、提拉速度为500μm/s及正硅酸乙酯与乙醇物质的量比为1∶30、提拉速度为1000μm/s的制备SiO_(2)薄膜的最大透过率分别高于未镀膜玻璃7.50%和6.71%,在400~1100 nm波长范围内的平均透过率分别高于未镀膜玻璃5.94%和5.59%,表明SiO_(2)薄膜的减反射性能具有较好的耐久性。结论采用碱催化溶胶-凝胶法在玻璃上制备的SiO_(2)减反射薄膜具有超亲水性及优异的减反射耐久性,在太阳能电池玻璃盖板上具有潜在的应用价值。

热处理工艺对SLM打印波纹管耐撞性影响

为了获得稳定的轴对称变形模式和较好的耐撞性,设计轴向轮廓为正弦曲线的薄壁锥形波纹管。采用SLM制备AlSi10Mg合金试样和波纹管,并进行拉伸实验和波纹管轴向压溃实验,采用实验和数值仿真研究退火、固溶和T6热处理对波纹管轴向压缩下耐撞性的影响。研究结果表明:265℃退火热处理后,波纹管在静压下出现裂纹失效,与未热处理相比,AlSi10Mg合金试样经T6热处理后伸长率由4.7%提升至13.8%,拉伸强度由413.2 MPa降低至135.3 MPa。波纹管压溃力波动范围随伸长率增加而减小。经265℃、2 h退火处理后,波纹管峰值力达到最大为7.11 kN,压溃力波动幅值最大,压溃力效率为65.9%。经T6热处理后,波纹管峰值力降到最小,为4.75 kN,压溃力波动为所有波纹管中最小,吸能量最少,为279.12 J。与T6热处理相比,经295℃、3 h退火热处理后,波纹管平均压溃力达到5.09 kN,提升了16%,吸能量达到最大,为341.24 J,提升了18.5%。为了提升SLM打印的波纹管耐撞击性能,热处理工艺需要在保证伸长率的同时尽量提高材料强度。

外部经济不确定性与中国家庭经济活动

当今世界,国外环境日趋复杂,不确定性因素明显增加,将对中国家庭经济活动产生深远影响。在测算中国面临的外部经济不确定性的基础上,利用中国家庭金融调查数据(CHFS)和分位数回归方法,实证研究了外部经济不确定性对中国家庭收入、消费和风险资产配置的影响。研究发现:外部经济不确定性对家庭总收入和家庭总消费均存在显著的负向作用,且这种负向作用随着收入水平和消费水平的提高而增大;外部经济不确定性对不同消费水平群体的家庭耐用品消费均有明显的负向影响,对中等消费水平群体的负面影响最大。此外,外部经济不确定性对中国家庭收入和消费的影响表现出区域差异性和城乡差异性,在外向型产业占比更大的东部地区和经济发展水平较低的农村地区,家庭收入和消费受到外部经济不确定性的冲击更大。而拥有社会保险或商业保险是缓解外部经济不确定性对家庭经济活动负面影响的重要调节方式。进一步分析表明,当家庭面临更大的外部经济不确定性时,会减少对风险资产的持有,增加持有无风险资产。

再生细骨料混凝土的性能研究进展

合理使用再生细骨料(以下简称RFA)可同时解决建筑垃圾的资源化利用问题和天然砂、石过度开采引起的环境问题。介绍了RFA的颗粒形状、空隙率、吸水率、有害物质含量等性能,总结了RFA的性能强化措施,综述了再生细骨料混凝土(以下简称RFAC)的工作性、力学性能和耐久性能,并对其机理进行了分析,可为RFA的进一步推广应用提供参考。