Study On Test Methods For Combustion Properties Of Asphalt And Flame-retardant Mechanism Of Filler

With the continuous development of highway construction, the length of highway tunnels is increasing year by year, the safety and comfort of roads have to satisfy a higher standard. Nowadays, a large number of long tunnels have used asphalt concrete pavement. However, the asphalt which is a flammable material in the air can burn at a high temperature to emit a lot of smoke and toxic gas. The toxic gas, smoke and heat which are producted by asphalt burning are difficult to dissipate in the relatively closed space which lead to the difficulty for personnel escaping after the accident, always bring disastrous accidents, heavy losses, and even endanger human life. Therefore, it is significant to research the flame retardant of the asphalt concrete pavement in long tunnels for ensuring operational safety.First, this paper introduces the research status of asphalt retardant at home and abroad, including the research development of the flame-retardant technology, the flame-retardant mechanism of the asphalt and the testing and evaluation method of flame-retardant properties of the flame-retardant asphalt. And then, it analyzes the difference between the combustion characteristics and testing methods of textile, plastic and rubber on comparison, it also discusses the research problems about the flame-retardant asphalt currently existed in China.Secondly, the combustion performance of asphalt, rubber asphalt, SBS modified asphalt, fire-retardant asphalt and flame-retardant asphalt mortar are tested by digital oxygen index instrument, and also the influence of the samples size, ignition control time, conditioning time on test results of the asphalt combustion performance is analyzed. The research results indicate that the results vary greatly with the actual if the chemical industry test standards is totally used to evaluate the combustion performance of asphalt. Through a large number of tests, it is more reasonable to test and evaluate the combustion performance of asphalt when the sample section size is 4mm×6mm or 4mm×7mm, the length is 80mm~100mm, the ignition control time is extended to 40s, and conditioning time is set to 12h.Thirdly, the cnooc matrix asphalt is used as the foundational material. the flame-retardant property of the asphalt which was added to different ratios of a variety of flame retardants and fillers is tested. Then,flame-retardant mechanism of the filler is revealed deeply through characterizing and analyzing the various flame retardants and fillers depend on the specific surface area, particle size composition, SEM electron micrographs. Experimental results show that both flame retardant or filler have some effect on flame-retardant properties of asphalt. For the powdered ore, cement, stone dust, flame-retardant properties of them were mainly provided by the dilution of the asphalt. When the addition is smaller, the larger the specific surface area is, the more powerful the dilution to asphalt is, the better flame-retardant properties is. The more uniform grain size distribution is, the more regular the external form is, the better flame-retardant properties is. When the addition is comparatively heavy, the larger the specific surface area is, the easier mastic asphalt is saturated on the lower of stability and compatibility, the slower the rise of flame-retardant properties is. Because specific surface area of powdered ore is smaller, it still effectively improves the flame-retardant properties of mastic asphalt when the addition is very heavy. For the three kinds of flame-retardant, zinc borate, antimony trioxide, flame retardant asphalt, their flame-retardant properties is not only provided by physical and chemical properties of the material, but also they are relevant to the material specific surface, particle size composition and the external morphology. However, the former is the primary factor for the flame-retardant properties.Finally, the research results are summarized. Acoording to the above empirical findings, further research direction of the flame-retardant properties of asphalt pavement is provided.