A review of asphaltic crack healing approaches and Its mechanism

(e concept of self-healing has an excellent potential to extend the life of asphalt pavement. (is technology can be considered a sustainable technology due to its ability to reduce the utilization of asphalt mixture production materials used for road maintenance, polluting the environment. It is a complex physicochemical process wherein the molecular diffusion healing mechanisms in asphalt materials are inspired by self-healing polymeric systems, which describe the self-recovery behaviors based on polymer chain dynamics. Several methods have been adopted to improve the self-healing of asphalt, one of which is induction healing. It is the process of heating the asphalt pavement incorporated with an electrically conductive material such as steel fibers, wherein asphalt healing is undertaken via electric field induction. Induction healing via induction heating occurs with eddy current where the electric current flows within the conductive fibers when magnetically susceptible under the magnetic field. Microwave heating is another self-healing method similar to induction in which magnetic radiation is employed to treat asphalt mixtures instead of the electric field-induced induction healing processes. (e conductive fibers can absorb the electromagnetic (EM) waves to convert them into heat energy through doublet polarization, interface polarization, and electrical conduction dissipation when placed in the microwave field. (ese two types of heating systems, which are induction heating and microwave heating, are compared and discussed thoroughly in this study. Finally, some recommendations for the future development of selfhealing asphalt are proposed

Microwave non-destructive testing of coatings and paints using free space microwave measurement / Norhayati Hamzah ... [et al.]

Microwave nondestructive testing (MNDT) techniques are applied to evaluate quality of anti-corrosive protective coatings and paints on metal surfaces. A tree-space microwave measurement (FSMM) system is used for MNDT of protective coatings. The FSMM system consists of transmit and receive spotfocusing horn lens antennas, a vector network analyzer, mode transitions and a computer. Diffraction effects at the edges of the sample are minimized by using spot-focusing horn lens antennas. Errors due to multiple reflections between antennas are corrected by using free-space LRL (line, reflect, line) calibration technique. We have measured complex reflection coefficient of polyurethane based paint which is coated on brass plates

ELECTRICAL CHARACTERIZATION AND APPLICATIONS OF CONDUCTIVE INFRASTRUCTURE MATERIALS

The feasibility of multifunctional applications of electrically conductive asphalt concrete is investigated. The conductive asphalt concrete has a huge potential for various multifunctional applications such as self-healing, self-sensing, and deicing. This study examines the method of controlling conductivity of asphalt composites, electrical characterization of the composites with alternating current impedance spectroscopy (ACIS), application for damage self-sensing, and application for removing snow and ice on pavements. Aiming to control the electrical conductivity of asphalt concrete with a smooth transition from insulated to conductive phase, nine types of graphite having different particle shape, size, and origin were mixed with asphalt binders, and their effects on imparting conductivity were investigated. The natural flake graphite is effective to mitigate the percolation threshold, and a sufficiently high conductivity (up to 10^2 Ω·cm) can be achieved by replacing a part of fillers only with the graphite. For the electrical characterization of the conductive asphalt composites, ACIS is employed. Through this technique, the equivalent electrical circuits in various levels of conductivity is constructed for the first time. The results show that a specific conductivity range containing 20-25% flake graphite by weight of the asphalt mastic is suitable for sensing applications. Self-sensing of damage is one of probable multifunctional applications of the conductive asphalt concrete, and its feasibility is investigated using ACIS. The experiments with dry and wet conditions show that the real and imaginary impedance increase with the increase of the damage, while the capacitance value does not show a clear relationship with the damage evolution. The results also show that the distance between electrodes is important for measuring damage with ACIS. The feasibility of the heated pavement using the conductive asphalt as a cost-effective and pollution-free solution was investigated. Bench scale slab heating test, non-steady state heat transfer analysis, and life-cycle assessment (LCA) were conducted. The results of these methodologies reveal that the heating capacity of the conductive asphalt is sufficient for deicing on pavement surfaces. The electrical and mechanical data obtained from this study provide essential information on multifunctional applications of conductive asphalt concrete, which will lead to technical innovations for more sustainable pavement systems

In situ water content measurement of compacted highway subgrades using time domain reflectometry

The water content is a principle factor of subgrade soil stability in shallow foundation pavement systems. Currently data do not exist for seasonal subgrade water content changes in Tennessee pavement systems. Four test sites across the state were instrumented with equipment to monitor subgrade and flexible asphalt pavement water content and temperature, water infiltrated through the pavement layers, and climatic conditions. These data will later be used to develop a rational method of flexible asphalt pavement design that accounts for environmental factors and seasonal water content changes. Five-segment TDR probes, manufactured by Environmental Sensors, were installed in the soil subgrade, the stone base, and the asphalt stabilized base. Single segment TDR probes, constructed in the laboratory, were installed in the asphaltic concrete. The multiple-segment TDR probes allow changes in water content to be tracked two-dimensionally, between the probes and along probe segments. Temperature sensors were installed at depths corresponding to the soil subgrade and the stone base TDR probes. Three temperature sensors were also installed in the top 20 cm of the pavement. A weather station was installed at each test site to monitor air temperature, relative humidity, solar radiation, wind speed, and rainfall. The Moisture Point TDR system, manufactured by Environmental Sensors, was designed for use in agricultural soils. The materials in which the TDR probes were installed at each test site are quite dissimilar from agricultural soils. For this reason, a calibration study was performed with the Moisture Point TDR equipment using test site subgrade soils and a single crusher run gravel sample. Ten previously published TDR calibration equations were evaluated to determine which equation most accurately predicts water content for the subgrade soils and for crusher run gravel. The relationship between inverse signal velocity and water content proposed by Herkelrath et al. (1991) most accurately predicted water content for all subgrade soils; however, this relationship requires the derivation of a soil specific slope and intercept. The three- and four-phase dielectric mixing models, proposed by Dobson et al (1985) and rewritten to calculate volumetric water content by Weitz et al. (1997), provided results within the accuracy of the Moisture Point equipment for subgrade soils. The equation proposed by Baran (1994) most accurately predicted water contents for the crusher run gravel

A review of pavement assessment using ground penetrating radar (GPR)

The use of GPR to obtain information on pavement structures has greatly developed over the past 20 to 30 years. The early 1980’s saw the first major developments of GPR for pavement applications and it is now an accepted technique for pavement investigation. GPR has a proven ability to obtain a variety of information on parameters relating to the structure and materials of the pavement. Despite this, several hindrances to wider use of the technique exist, and there is a requirement to address a number of both perceived and real limitations of GPR use for pavement investigation. This paper aims to provide an up to date discussion and summary of the current and developing uses of GPR for pavement investigation, through reference to previous work and ongoing research,including that conducted by the authors. This paper is intended for both GPR specialists and pavement engineers, and reports the ability of GPR to obtain good data for the various uses described, and discusses the applicability,limitations, and scope of GPR for further developments in pavement investigation

Piezoresistivity of Electrically Conductive Asphalt Concrete

Electrically conductive asphalt concrete is considered as a multifunctional construction material due to its structural and non-structural functions. This study aims to investigate piezoresistivity of conductive asphalt concrete. Piezoresistivity is an electrical property of some materials which electrical resistivity changes with induced strain and subsequently, it has the potential for self-sensing smart technology. Graphite Powder F-516 with various contents was added into the asphalt mixtures to impart the electrical conductivity. Electrochemical impedance spectroscopy (EIS) was selected to measure the electrical properties of the specimens in dry and wet conditions, and low and high temperatures. The impedance measurement shows that the mixtures are conductive when 30% or higher portion of traditional filler were replaced with graphite. In highly conductive specimens containing 40% or higher graphite contents, moisture content does not have significant effect on the conductivity. The temperature of specimens changes the impedance: the impedance increases with the increase of temperature. A freeze-thaw cycle raises the impedance of specimens. Material Testing System was used to perform a uniaxial compression test (monotonic loading). Significant changes in impedance with loading are observed, but it is difficult to conclude whether the impedance changes are caused by strain or by damage