Anti-icing Asphalt Composites

The preparation technology of anti-icing filler, anti-icing composite materials and the testing technology of the ability of anti-icing of it are the foundation of the research of anti-icing asphalt pavement or self-ice-melting asphalt pavement. As one kind of self-ice-melting pavement technology, if the a nti-icing asphalt pavement can be used in high way construction widely, it will dramatically decrease the damage of the snow and frost to the transportation, save human life in traffic accidents may occur in bad weather, and save property and economic damages which cause by the snow and ice. The disaster of freezing rain and the large traffic jam following it raise more and more attention to this issue from researchers.In this paper, a method for preparing diatomite / chloride salt compound anti-icing filler was studied, and the anti-icing ability of anti-icing composite materials i.e. anti-icing asphalt mastic was tested. The analytical method of SEM, EDS, XRD, IR, and TG/DTA are used to characterize the anti-icing fillers.1. This study investigated one kind of powder replacement anti-icing filler, which can be used in anti-icing asphalt mastics. Nonsolvent induced precipitation method, which in the thermodynamic system far from equilibrium and with the ultrasonic vibration field condition, was used to prepare micron sized granule composites of sodium chloride crystal and diatomite, of sodium chloride crystal and diatomite composite modified with nano-Si O2, and of potassium chloride crystal and diatomite composite modified with nano-Si O2, which is the anti-icing filler. Diatomite and chloride salt crystal are mosaic and parceled mutually in microscopic level. The particles are uniform in size of 10 to 50μm and hygroscopic. In dry condition, they are easy to flow and don’t agglomerate. In the crystal nucleation and growth stages, the add of nano-silica will change the shape of the composite particles, reducing the area of diatomaceous which exposed to the surface of the composite particles, and reducing the combination of diatomite and NaCl. After the replacement of NaCl by KCl, the size of the composite particles is dwindled, and the crystals of KCl become gyroidal distorted. This may due to the saturation concentration of KCl is higher than that of Na Cl.2. After the coated modification, the anti-icing filler become hydrophobic. Also the hygroscopic ability of the filler is changed. Moisture absorbent tests showed a significant hygroscopic ability reduction in the sample, after coating the hygroscopic ratio of 72 h reduced from 68.6% to 14.8%. And the thermal analysis showed that the polymer material began to oxidation degradation above 250℃, indicating that this filler can meet the requirements of asphalt hot mix production process.3. Then, anti-icing mastics specimens of different anti-icing filler content were prepared by asphalt hot mix method. The SEM analysis of the mastics shows that it has micron sized compatible structure. Compare the specimen before and after the anti-icing experiment, it is can be found that due to the release of KCl salt, pits of micron sized appear on the specimen surface, which mainly about 10μm and generally no more than 50μm, showing the matrix of the asphalt mastic material is not damage.4. The freezing temperature test result in steady state conduction with temperature drop steps by steps shows, the freezing point of the water on the asphalt mastics surface decrease with the increase of content of anti-icing filler, while the lowest average freezing temperature is-6.5 ℃, and the lowest average frost temperature is-8.5℃. It is show that the temperature of dews become ice crystals floating above the liquid film is-7.5℃. This test shows that the anti-icing composite materials have the ability to prevent the form of ice and frost on its surface at certain temperature below zero.5. The ice melting rate tests show, at the room temperature, the ice melting rate of the asphalt mastics increase with the increase of the content of anti-icing filler, the speed of specimen of 50% content is about 3 times quicker than that of the 0% content.