A piezoelectric asphalt mixture and its load-piezoelectric-electrothermal conversion evaluation method

Abstract

The present invention provides a piezoelectric asphalt mixture and an evaluation method for load-piezoelectric-electrothermal conversion thereof, which belongs to the field of piezoelectric asphalt mixture evaluation, and solves the problems that it is difficult to collect, store, utilize, and evaluate electrical energy in piezoelectric pavements, and that the durability of self-healing asphalt is poor and the operation is complicated. The present invention firstly adopts the method of fully mixing polyvinylidene fluoride-hexafluoropropylene powder and carbon black powder with matrix asphalt to obtain modified asphalt with electrical activity and conductivity. AC-13F aggregate is selected, and 40% of the aggregates of 4.75 mm and above are replaced by equal volume of piezoelectric ceramic aggregates, and steel fibers are added to improve the conductivity of the mixture. The surface temperature change of the Marshall specimen after applying repeated loads is observed by an infrared thermal imager to evaluate the effect of load-generation-electrothermal energy conversion. The piezoelectric asphalt mixture and the evaluation method of load-piezoelectric-electrothermal conversion of the present invention can effectively utilize road pressure and vibration energy, and the generated electric heat can improve the self-healing performance of the asphalt mixture.

Description

Technical Field

[0001] The invention discloses a piezoelectric asphalt mixture and an evaluation method for load-piezoelectric-electrothermal conversion thereof, belonging to the field of piezoelectric asphalt mixture evaluation. Background Art

[0002] Since the 21st century, with the rapid growth of my country's national economy, the increasing comprehensive national strength, and the increasingly improved infrastructure construction, especially the sustained and rapid development of my country's highway construction, the demand for the maintenance and repair of asphalt pavement has also increased.

[0003] Asphalt is a complex mixed polymer material, and its physical properties follow the laws of polymer motion, the principle of stress relaxation, and the principle of time-temperature equivalence. Although asphalt concrete itself has certain self-repairing properties and has the ability to self-repair or self-heal, during the load interval, microcracks smaller than a certain scale (threshold scale) generated in asphalt concrete due to long-term service can be automatically healed, and its modulus and strength can be restored, and fatigue life can be extended. However, the repair ability of asphalt itself is limited and time-consuming, and when the temperature is too low or the crack is larger than the threshold scale for self-repair, it is difficult for asphalt to achieve self-repair.

[0004] Since the performance of asphalt roads depends not only on the performance of asphalt, the selection of aggregates and other materials is also very important. Without the influence of external factors, the self-healing performance of asphalt is very limited, so many self-healing asphalt roads rely on adding high-performance materials or increasing external energy input to achieve self-healing of road cracks.

[0005] At present, the induction or microwave heating technology and microcapsule technology are mainly used to improve the self-healing performance of asphalt. Induction heating is to increase the temperature of asphalt mixture, increase the diffusion rate and range of asphalt molecules, and accelerate the self-repair speed of asphalt materials through electromagnetic induction and microwave radiation. Microwave heating requires that the material has certain microwave absorption performance. The polar molecules in the material continue to move and collide under the action of microwave energy radiation, thereby generating heat energy. Microcapsule technology is to add microcapsules containing regeneration agents into the asphalt mixture. When the crack develops to the surface of the microcapsule, the shell of the microcapsule breaks under the action of stress concentration, and the internal regeneration agent diffuses through capillary action, so that the performance of the aged asphalt is restored and the cracks are closed. However, induction and microwave heating technology still require large engineering vehicles for processing, and the repair ability of microcapsule technology is significantly reduced after several damages, and the durability is weak.

[0006] At present, piezoelectric ceramics are mainly used for road energy collection. Energy collection refers to the use of various methods to capture energy in the environment. At present, it is mainly used to capture the pressure and vibration of vehicle loads on the road and convert them into electrical energy. In the process of piezoelectric ceramics collecting road energy for power generation, the collection and storage of electrical energy often become a problem.

[0007] It can be seen that there are deficiencies in the current self-healing asphalt roads and piezoelectric ceramic road power generation technologies. Induction heating technology still requires a lot of external energy input to achieve road heating and self-healing, and still requires a lot of manpower and material resources; the durability of microcapsule technology has many deficiencies, and the self-healing performance has significantly decreased after several cycles, and the subsequent repair problem still needs to be solved; the piezoelectric ceramic road power generation technology has serious problems in energy collection and loss during the energy collection process, and there are many difficulties in operation. Summary of the invention

[0008] (1) Technical issues

[0009] The purpose of the present invention is to provide a piezoelectric asphalt mixture and an evaluation method for its load-piezoelectric-electrothermal conversion, so as to solve the problems that electric energy is difficult to collect, store and utilize in the current piezoelectric ceramic power generation pavement, and at the same time solve the problems that the durability of self-healing asphalt pavement is poor and still requires a lot of manpower and material resources and the operation is complicated.

[0010] (2) Technical solution

[0011] In order to solve the problems of difficulty in collecting, storing and utilizing electric energy in piezoelectric ceramic power generation pavement, and at the same time solve the problems of poor durability and still requiring more manpower, material resources and complicated operation in the current self-healing asphalt pavement. The present invention first selects polyvinylidene fluoride-hexafluoropropylene as an asphalt modifier, and then according to the characteristics of polyvinylidene fluoride-hexafluoropropylene and asphalt, adds conductive carbon black to promote the transformation of polyvinylidene fluoride-hexafluoropropylene into an electrically active crystalline phase and improve the conductivity of asphalt, selects AC-13F grading, and replaces 40% of 4.75 mm and above aggregates with equal volume of piezoelectric ceramic aggregates, and adds steel fiber to the mixture to further improve the conductivity of the mixture, and its mass is 1% of the mass of aggregates and asphalt before the aggregates are replaced. Finally, an infrared thermal imager is used to observe the temperature change of the piezoelectric mixture after pressure and vibration, so as to evaluate the load-piezoelectric-electrical heat conversion effect of the asphalt mixture.

[0012] (3) Beneficial effects

[0013] With the increase of road use time and the rapid growth of total mileage, my country's road maintenance demand also shows a rapid growth trend. In addition, my country has long had the idea of ​​"focusing on construction and neglecting maintenance", which has led to a very weak foundation for highway maintenance. Especially for the early maintenance of crack development, it is difficult to find and handle it, and it is very difficult to maintain. If these early micro-damages and micro-cracks are not effectively handled, under the continued action of various factors such as load, temperature, and water, these micro-cracks will develop into more serious diseases, seriously affecting the subsequent road performance of asphalt roads, shortening the service life of roads, and increasing the cost of subsequent maintenance. The current self-healing asphalt research still has the disadvantages of complex operation and poor durability. The purpose of the present invention is a piezoelectric asphalt mixture and a load-piezoelectric-electrothermal conversion evaluation method, in which piezoelectric ceramic aggregates can convert the pressure and vibration of the road surface into electrical energy, and a part of the electrical energy generated in the conductive electroactive asphalt will be converted into thermal energy, so that the temperature of the asphalt road surface rises, and a part of the electrical energy will act on the electroactive crystals in the asphalt to improve the activity of the asphalt, thereby improving the self-healing ability of the asphalt road surface. In addition, the added steel fiber can improve conductivity and increase heat generation on the one hand, and on the other hand, as a fiber, it can also increase the tensile strength of concrete and reduce the expansion of cracks. DETAILED DESCRIPTION

[0014] The purpose of the present invention is to provide a piezoelectric asphalt mixture and an evaluation method for load-piezoelectric-electrothermal conversion thereof, and the specific implementation steps are as follows:

[0015] (1) heating the base asphalt to 150° C., adding 5% of polyvinylidene fluoride-hexafluoropropylene by weight of the base asphalt and 0.5% of carbon black powder by weight of the base asphalt, shearing the mixture at 150° C. for 1 hour using a high-speed shearing machine, and aging the mixture in an oven at 150° C. for 1 hour to obtain an electroactive polymer and carbon black composite modified asphalt;

[0016] (2) According to the AC-13F asphalt mixture gradation design results, 40% of the basalt coarse aggregate with a particle size of 4.75 mm and above was replaced by an equal volume of piezoelectric ceramic aggregates with the same particle size, and the Marshall design method was used to determine the optimal asphalt-stone ratio of the piezoelectric asphalt mixture;

[0017] (3) The steel fiber content is 1% of the original aggregate mass before the aggregate is replaced, and the optimal asphalt-stone ratio is increased by 0.02%. Basalt aggregate, piezoelectric ceramic aggregate and steel fiber are weighed according to the AC-13F asphalt mixture grading and placed in an oven at 180°C for insulation;

[0018] (4) adding basalt aggregate, piezoelectric ceramic aggregate and steel fiber into a mixing pot at 160° C. in proportion and stirring for 60 seconds, heating the electroactive polymer and carbon black composite modified asphalt prepared in step (1) to 160° C., adding the required mass of composite modified asphalt according to the adjusted optimal asphalt-rock ratio determined in step (3), and stirring for another 60 seconds to prepare an electroactive polymer and carbon black composite modified asphalt mixture containing piezoelectric ceramic aggregate and steel fiber, and simultaneously preparing a control group of ordinary asphalt mixture using the original AC-13F asphalt mixture grading;

[0019] (5) Prepare a standard Marshall specimen, and use a universal material testing machine to measure the breaking compressive load between the top and bottom surfaces of the Marshall specimen. Wrap the Marshall specimen with insulation material on all sides, and apply a repeated compressive load between the top and bottom surfaces of the specimen with 50% of the breaking compressive load as the control amount. The loading rate is 30 times / minute and lasts for 10 minutes. Immediately use an infrared thermal imager to observe the change in surface temperature of the Marshall specimen, so as to evaluate the load-piezoelectric-electrothermal conversion efficiency of the electroactive polymer and carbon black composite modified conductive asphalt mixture.

Claims

1. A piezoelectric asphalt mixture and a method for evaluating load-piezoelectric-electrothermal conversion thereof, characterized in that The specific implementation steps are as follows: (1) heating the base asphalt to 150° C., adding 5% of polyvinylidene fluoride-hexafluoropropylene by weight of the base asphalt and 0.5% of carbon black powder by weight of the base asphalt, shearing the mixture at 150° C. for 1 hour using a high-speed shearing machine, and aging the mixture in an oven at 150° C. for 1 hour to obtain an electroactive polymer and carbon black composite modified asphalt; (2) According to the AC-13F asphalt mixture gradation design results, 40% of the basalt coarse aggregate with a particle size of 4.75 mm and above was replaced by an equal volume of piezoelectric ceramic aggregates with the same particle size, and the Marshall design method was used to determine the optimal asphalt-stone ratio of the piezoelectric asphalt mixture; (3) The steel fiber content is 1% of the original aggregate mass before the aggregate is replaced, and the optimal asphalt-stone ratio is increased by 0.02%. Basalt aggregate, piezoelectric ceramic aggregate and steel fiber are weighed according to the AC-13F asphalt mixture grading and placed in an oven at 180°C for insulation; (4) adding basalt aggregate, piezoelectric ceramic aggregate and steel fiber into a mixing pot at 160° C. in proportion and stirring for 60 seconds, heating the electroactive polymer and carbon black composite modified asphalt prepared in step (1) to 160° C., adding the required mass of composite modified asphalt according to the adjusted optimal asphalt-rock ratio determined in step (3), and stirring for another 60 seconds to prepare an electroactive polymer and carbon black composite modified asphalt mixture containing piezoelectric ceramic aggregate and steel fiber, and simultaneously preparing a control group of ordinary asphalt mixture using the original AC-13F asphalt mixture grading; (5) Prepare a standard Marshall specimen, and use a universal material testing machine to measure the breaking compressive load between the top and bottom surfaces of the Marshall specimen. Wrap the Marshall specimen with insulation material on all sides, and apply a repeated compressive load between the top and bottom surfaces of the specimen with 50% of the breaking compressive load as the control amount. The loading rate is 30 times / minute and lasts for 10 minutes. Immediately use an infrared thermal imager to observe the change in surface temperature of the Marshall specimen, so as to evaluate the load-piezoelectric-electrothermal conversion efficiency of the electroactive polymer and carbon black composite modified conductive asphalt mixture.