Papers by Keyword: Conductive Asphalt Concrete

Abstract: Asphalt concrete is an insulating material. Conductive materials are added to asphalt concrete in order that improving the conductivity. Conductive asphalt concrete (CAC) has become a promising method to snow melting and self-monitoring. In this study, the piezoresistance of CAC which can be improved the conductivity through graphite are analyzed. Based on the interparticle separation and bitumen film-thickness of graphite particle, a model has been developed to predict the piezoresistance under the applied stress. The influences of applied stress, graphite diameter, graphite volume fraction, compressive modulus on the piezoresistance are interpreted through laboratory experiments. Both the numerical and experimental results show that the theoretical data obtained from the model are found to agree with the experimental ones fairly well. In addition, it was found that all these parameters influence the piezoresistance by altering the change process of interparticle separation of graphite.

Abstract: Conductive asphalt concrete, a kind of intelligent materials, can serve as asphalt solar collector, asphalt heater and self monitor. And moisture damage is one of the most common performance degradation of asphalt concrete. This paper investigates the volume properties of conductive asphalt concrete based on Freeze-thaw cycles. Marshall specimen was frozen and thawed repeatedly and a cycle consists 16h at -18oC and 8h at 60oC. The change of air void and weight loss ratio were chosen to evaluate the moisture resistance of conductive asphalt concrete. Three types of asphalt mixture (control, CAC 1 and CAC 2) were used to study the effect of initial void and material composition on moisture resistance. The results show that both the framework structures and the material composition have a great effect on antifreeze-thaw property of asphalt concrete, which provides an efficient guidance for application of this technology in pavement.

Abstract: Aggregate distribution of asphalt mixture had an obvious characteristic of fractal. Based on fractal theory, the distribution function of aggregate of conductive asphalt mixture based on the granular fractal model was deduced. This paper used linear regression analysis to different gradings to get the grading fractal dimension of conductive asphalt mixture and the conductivity of the mixture was tested. Test results indicated that the grading fractal dimension of conductive asphalt mixture was controled by the fine aggregate. On the other hand, the fractal dimension had a congruent relationship with conductivity. The conductive asphalt mixture had good pavement performance and conductive when the fractal dimension of AC-20 grading ranged from 2.43 to 2.53. The fractal dimension can be used as a quantification index of grading evaluation.

Abstract: The key point of preparing conductive asphalt concrete for deicing and snow melting is pavement performance must satisfy the requirements before it can melt snow successfully. This study prefers to prepare electrically conductive asphalt concrete choosing steel slag as the whole aggregates and conductive minerals, while mixed with graphite and carbon fiber. Moisture susceptibility has been evaluated through water-saturated Marshall Stability test and indirect tensile splitting strength test. High temperature performance and fatigue performance were analyzed through dynamic creep test and indirect tensile fatigue test. Results indicate: High temperature performance of steel slag conductive asphalt concrete is better than ordinary basalt asphalt concrete, while its moisture susceptibility and fatigue performance is not good enough and need to be improved.

Abstract: In order to solve the snowing and anti-icing problems, the electric heating asphalt concrete program was proposed. Conductive asphalt concrete samples, with copper mesh electrodes, with its size 20cm × 10cm were made, which was tested by three kinds of voltage heating temperature, and using natural snow to verify the hot performance. Experiments showed that the different points on surface have the different heating performances. When voltages are respectively in 12V, 24V, 36V, the temperature are at the range of 14.6~16°C, 11.7~29.6°C, 15~55°C. Natural snow melting experiments outside showed that the conductive asphalt concrete has a good effect, which becomes significant the sample is keeping with the power for 20 ~ 40 min. With time going on, the snow tends to disappearing completely, and the temperature of snow sample is always lower than the ambient temperature.

Abstract: It is currently interesting to use thermal or electrical conductive asphalt concrete for snow-melting and maintenance of asphalt pavements in winter. The addition of conductive fillers may have negative effects on the mechanical properties of asphalt concrete. The performance of conductive asphalt concrete is greatly affected by the initial crack and its propagation. Laboratory tests for neat and conductive asphalt concrete include Dynamic Modulus Test (DMT) and Indirect Tensile Fatigue Test (ITFT). DMT tests indicates that the value of dynamic modulus of asphalt concrete decreases with the increasing graphite content. It means that the conductive asphalt concrete achieves lower stiffness. It can be concluded from ITFT tests that the fatigue life (load cycle times) of conductive asphalt concrete is more than neat ones when stress level is under 1.0 MPa. Meanwhile higher fatigue resistance of conductive asphalt concrete is observed when carbon fibers (2 weight % of total aggregate) were added together with 22% graphite, especially at low stress levels.