The Frost-resisting Durability of High Strength Self-Compacting Pervious Concrete in Deicing Salt Environment

A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%, 10%, and 20%) was investigated. The mass-loss rate, relative dynamic modulus of elasticity, compressive strength, flexural strength and hydraulic conductivity of SCPC after 300 freeze-thaw cycles were measured to evaluate the frost-resisting durability. In addition, the microstructures of SCPC near the top-bottom interconnected pores after 300 freeze-thaw cycles were observed by SEM. The results show that the high strength SCPC possesses much better frost-resisting durability than traditional pervious concrete(TPC) after 300 freeze-thaw cycles, which can be used in heavy loading roads. The most serious freeze-thaw damage emerges in the SCPC immersed in the 3% of Na Cl solution, while there is no obvious damage in 20% of Na Cl solution. Furthermore, it can be deduced that the high strength SCPC can be used for 100 years in a cold environment.

Influential Factors on Deicing Performance of Electrically Conductive Concrete Pavement

The deicing experiment of carbon fiber reinforced electrically conductive concrete （CFRC） slab was conducted in laboratory at first, then the deicing process of CFRC parement was analyzed by means of finite element method （FEM）. At last, based on the energy conservation law and the computing restdts of finite element method, the influential factors including the setting of electric heating layer, environmental temperature, the thickness of ice, material parameters, and deicing power on deicing performance and energy consumption were discussed.

Experimental Study on Deicing Performance of Carbon Fiber Reinforced Conductive Concrete

Carbon fiber reinforced concrete (CFRC) is a kind of good electrothermal material. When connected to an external power supply, stable and uniform heat suitable for deicing application is generated in the CFRC slab. Electric heating and deicing experiments of carbon fiber reinforced concrete slab were carried out in laboratory, and the effect of the temperature and thickness of ice, the thermal conductivity of CFRC, and power output on deicing performance and energy consumption were investigated. The experimental results indicate that it is an effective method to utilize the thermal energy produced by CFRC slab to deice. The time to melt the ice completely decreases with increasing power output and ice temperature, and increases with increasing thickness of the ice. The energy consumption to melt 2 mm thickness of ice varies approximately linearly from 0.556 to 0.846 kW·h/m2 as the initial temperature ranges from -3℃ to - 18℃. CFRC with good thermal conduction can reduce temperature difference in CFRC slab effectively.

Numerical Simulation of an Airfoil Electrothermal-Deicing-System in the Framework of a Coupled Moving-Boundary Method

A numerical method for the analysis of the electrothermal deicing system for an airfoil is developed taking into account mass and heat exchange at the moving boundary that separates the water film created due to droplet impingement and the ice accretion region.The method relies on a Eulerian approach(used to capture droplet dynamics)and an unsteady heat transfer model(specifically conceived for a multilayer electrothermal problem on the basis of the enthalpy theory and a phase-change correction approach).Through application of the continuous boundary condition for temperature and heat flux at the coupled movingboundary,several simulations of ice accretion,melting and shedding,runback water flow and refreezing phenomena during the electrothermal deicing process are conducted.Finally,the results are verified via comparison with experimental data.A rich set of data concerning the dynamic evolution of the distribution of surface temperature,water film height and ice shape is presented and critically discussed.

Protection and Treatment of Landscape Plant Secondary Disasters (Deicing Agent Damage) Caused by Extreme Weather

Deicing agent is always applied to alleviate urban traffic pressure after snowing in winter,however,such a snow melting agent is extremely harmful for landscape plants.To eliminate or avoid such damages,we have been actively exploring protection and treatment means.By analyzing the protection of landscape plants before using the deicing agent and the treatment after being damaged by the salt,the paper described how landscaping industry of Beijing handled extreme weather and influence of certain urban environment on landscape plants in a high-efficiency and low-cost way,and then figured out the balance point of normal social life and healthy development of ecological environment.

The Third-Order Viscoelastic Acoustic Model Enables an Ice-Detection System for a Smart Deicing of Wind-Turbine Blade Shells

The present work is based on the third-order partial differential equation (PDE) of acoustics of viscoelastic solids for the quasi-equilibrium (QE) component of the average normal stress. This PDE includes the stress-relaxation time (SRT) for the material and is applicable at any value of the SRT. The notion of a smart deicing system (SDS) for blade shells (BSs) of a wind turbine is specified. The work considers the stress in a BS as the one caused by the operational load on the BS. The work develops key design issues of a prospective ice-detection system (IDS) able to supply an array of the heating elements of an SDS with the element-individual spatiotemporal data and procedures for identification of the material parameters of atmospheric-ice (AI) layer accreted on the outer surfaces of the BSs. Both the SDS and IDS flexibly allow for complex, curvilinear and space-time-varying shapes of BSs. The proposed IDS presumes monitoring of the QE components of the normal stresses in BSs. The IDS is supposed to include an array of pressure-sensing resistors, also known as force-sensing resistors (FSRs), and communication hardware, as well as the parameter-identification software package (PISP), which provides the identification on the basis of the aforementioned PDE and the data measured by the FSRs. The IDS does not have hardware components located outside the outer surfaces of, or implanted in, BSs. The FSR array and communication hardware are reliable, and both cost- and energy-efficient. The present work extends methods of structural-health/operational-load monitoring (SH/OL-M) with measurements of the operational-load-caused stress in closed solid shells and, if the prospective PISP is used, endows the methods with identification of material parameters of the shells. The identification algorithms that can underlie the PISP are computationally efficient and suitable for implementation in the real-time mode. The identification model and algorithms can deal with not only the single-layer systems such as the BS layer without the AI layer or two-layer systems but also multi-layer systems. The outcomes can be applied to not only BSs of wind turbines but also non-QE closed single- or multi-layer deformable solid shells of various engineering systems (e.g., the shells of driver or passenger compartments of ships, cars, busses, airplanes, and other vehicles). The proposed monitoring of the normal-stress QE component in the mentioned shells extends the methods of SH/OL-M. The topic for the nearest research is a better adjustment of the settings for the FSR-based measurement of the mentioned components and a calibration of the parameter-identification model and algorithms, as well as the resulting improvement of the PISP.

面向未来低碳道路养护的超薄罩面功能性研究综述

Highway maintenance mileage reached 5.25 million kilometers in China by 2021.Ultra-thin overlay is one of the most commonly used maintenance technologies,which can significantly enhance the economic and environmental benefits of pavements.To promote the low-carbon development of ultrathin overlays,this paper mainly studied the mechanism and influencing factors of several ultra-thin overlay functions.Firstly,the skid resistance,noise reduction,rutting resistance,and crack resistance of ultrathin overlays were evaluated.The results indicated that the high-quality aggregates improved the skid and rutting resistance of ultra-thin overlay by 5%-20%.The optimized gradations and modified binders reduced noise of ultra-thin overlay by 0.4-6.0 dB.The high viscosity modified binders improved the rutting resistance of ultra-thin overlay by about 10%-130%.Basalt fiber improved the cracking resistance of ultra-thin overlay by more than 20%.Due to the thinner thickness and better road performance,the performance-based engineering cost of ultra-thin overlay was reduced by about 30%-40%compared with conventional overlays.Secondly,several environmentally friendly functions of ultra-thin overlay were investigated,including snow melting and deicing,exhaust gas purification and pavement cooling.The lower thickness of ultra-thin overlay was conducive to the diffusion of chloride-based materials to the pavement surface.Therefore,the snow melting effect of self-ice-melting was better.In addition,the ultra-thin overlay mixture containing photocatalytic materials could decompose 20%-50%of the exhaust gas.The colored ultra-thin overlay was able to reduce the temperature of the pavement by up to 8.1℃.The temperature difference between the upper and lower surfaces of the ultra-thin overlay containing thermal resistance materials could reach up to 12.8℃.In addition,numerous typical global engineering applications of functional ultra-thin overlay were summarized.This review can help better understand the functionality of ultra-thin overlays and promote the realization of future multi-functional and low-carbon road maintenance.

Review of ice-pavement adhesion study and development of hydrophobic surface in pavement deicing

Ice adhesion to materials is a significant concern in many fields. Hydrophobic surface has been used for anti-icing in fields of aircraft or transmission line, which prove to be efficacious and economical. However, such technique is seldom employed for road deicing, because of the texture and service environment of pavement. Instead, deicers such as rock salt are frequently used, which leads to serious corrosion problem of roads and bridges. In this paper, a number of studies that characterize mechanism of ice adhesion to common substrates, specifically to pavement, are reviewed. The most important researches undertaken on ice adhesion strength affecting factors are presented. An overview of studies carried out to find hydrophobie surface for asphalt and cement concrete pavement antiicing are presented. It was verified that the hydrophobicity had high correlation with icephobicity, and nano-engineered asphalt and cement concrete pavement surface exhibited favorable hydrophobicity, and also had good performance on weakening pavement-ice bonding. However, most ice-repelling pavements obtain hydrophobic surface via low surface energy coating, which could not exist on pavement for a long time under wheel abrasion. And the nano/micro structures on hydrophobic surfaces are also vulnerable and consumable. Thus, the long-term effect of hydrophobic surface still need to be improved, and durability of the hydrophobic surface should be the research and development priorities of ice-repelling pavement.

Intersection-pavement de-icing: comprehensive review and the state of the practice

Winter maintenance operations are crucial for pedestrian and motorist safety and public mobility on urban streets and highways in cold regions, especially during winter storms. This study provides a comprehensive literature review of existing deicing technologies, with emphasis on electrical resistance-heating deicing technologies for possible applications in areas with concentrated traffic, such as street intersections and crosswalks. A thorough review of existing and emerging deicing technology for snow/ice melting was conducted. The performance of various deicing methods was evaluated and the installation and operation cost of the electrical resistance-heating methods compared. Finally, current state of the practice of intersection/crosswalk winter maintenance was surveyed among state departments of transportation in North America. The intersection/crosswalk winter maintenance procedure adopted by the State of Alaska Department of Transportation and Public Facilities was described, and the annual winter maintenance and operation cost per intersection was estimated. It was found that the annual energy cost of an electrical resistance-heating method such as the carbon-fiber-tape deicing technology is about the same as the average annual maintenance and operation cost of current practice. In addition, an automatic electrical resistance-heating deicing system will bring benefits such as minimized delay time and improved safety for pedestrian and vehicular traffic in an urban application.

Experimental investigation on ice-breaking performance of a novel plasma striker

Aircraft icing has long been a plague to aviation for its serious threat to flight safety.Recently,researches about a newly proposed deicing method based on Plasma Synthetic Jet Actuator(PSJA)have just started.To meet the requirements of in-flight deicing,structure of PSJA needs to be adjusted.This paper completed the detailed design and experimental validation of a novel plasma striker,which was a modified version of PSJA.Influences of mass of the moving part and rod shapes on the ice-breaking performances were also studied.Besides,a“conical-nosed rod configuration”was proposed.Its purpose was to ensure a good ice-breaking performance of the plasma striker on long ice,by generating a splitting failure.Results show that,though mass of the moving part was just several grams,ice-breaking performance was better when the mass was lighter.The rectangular rod could generate an elliptical circumferential crack,whose major axis was parallel to the direction of the long side of the rectangular rod.And the“conical-nosed rod”concept was verified to be able to generate a splitting crack which can spread completely to the far end of long ice,and the crack direction was parallel to edge line of the cone.In general,the plasma striker has the advantages of simple structure,low energy consumption,little harm to the flow field and the aircraft skin.Simulations will be carried out in future works to study in detail the working process of the plasma striker.

基于相变材料的仿生太阳能防冰/除冰材料

太阳能除冰是环境友好的新型除冰/防冰方法,然而太阳能辐射的间歇性导致光热效率降低,限制了其发展.本文以膨胀石墨为光热载体,通过真空浸渍法将相变剂与之复合,再利用聚二甲基硅氧烷(PDMS)热固定型得到光热相变复合材料,并探究了其光热转化性能与防冰/除冰能力.结果表明复合材料不仅能实现光热转化,同时由于相变剂的作用能够进行热能的存储与释放,且表现出优越的防冰/除冰性能.在-40℃,一个太阳光强的条件下,材料表面的液滴延缓结冰时间超过2 h,在不同环境温度下表面除冰速率最高可达2.21 kg m^(-2)h^(-1).此外,此光热相变复合材料还表现出极高的可重复利用性.该材料是一类很有应用前景的高效光热防冰/除冰材料.

Enhanced electrothermal effect of carbon fibrous composites decorated with high conductive carbon nanotube webs

Literature has demonstrated that Carbon Nanotubes(CNTs) can greatly enhance the electrical conductivity and matrix-dominated mechanical properties of fibrous composites. However, electrothermal coupling effect of CNTs on Carbon Fiber Reinforced Plastics(CFRPs) has scarcely been considered. This work prepared and introduced thin and porous CNT webs to the surface or/and interface of a CFRP to enhance its electrothermal properties. The results show that CNT webs can enhance the transverse electrical conductivities of the CFRP by 231%-519% in a current range of 50–150mA, when compared to the base-CFRP. Also, the surface temperature of CNT webs decorated CFRP can be improved by 20.5–32.3℃ within 3min showing a self-heating rate of 6.8–10.8℃/min just with an applied voltage of 20–30V, increased by 152%-177% when compared to the base-CFRP(2.7–3.9℃/min). Also, deicing can be finished within 4–10min with a voltage of 18V and an input power of 246W/m^(2). Moreover, the electrothermal processes nearly have no negative effect on the mechanical properties of the CFRP. The relatively low input power and short response time for deicing make the CNT webs decorated CFRP may be a potential new generation for aeronautical deicing structure.