Design And Performance Of Fire-ertarding The Asphalt With The Nano-flame Retardants

With the rapid development of our economy and the implementation of the westerndevelopment strategy, a large number of highways are built in the western plateaumountain, so the number of road tunnels is also increasing. In order to meetrequirements of tunnel pavement, the asphalt pavement is gradually replacing thetraditional cement concrete pavement, to become the mainstream of the tunnelpavement. However, when the tunnel pavement fired, the flammability of asphaltpavement may cause burning violently, great casualties and economic loss, thusstudying flame retardancy of the asphalt pavement has the vital significance, meetingthe special using environment of tunnel.Taking account of the flame retardant (FR) used in the polymers, the synergisticeffect was achieved via incorperating the nanoparticles additives and traditional FR intothe matrix asphalt.and the aim in our study was to reduce the dosage of the FR andimprove the FR properties while maintaining the performace of the asphalt.First, according to the choosing principle of FR, the paper chose flame retardants for:decabromodiphenyl ethane (DBPE), antimony trioxide (Sb2O3), the ordinary ZincBorate (ZB) reaching to micron level in the particle size and nano Zinc Borate(nano-ZB). Among them, nano-ZB was made in the laboratory by zinc oxide and boricacid as raw materials, the synthesis of oleic acid as a surface modifier. Then chracterednano-ZB by the scanning electron microscopy (SEM), contact angle, infraredspectroscopy and thermal gravimetric analysis, tests showed: oleic acid carboxyl(-COO-) had been modified to the surface of ZB, the thickness of ZB particle was60~70nm, the contact angle θ was122.62°, so synthetic ZB was hydrophobic lipophilicsheet nanostructures. The nano ZB, DBPE and Sb2O3was composed of FR program A,ordinary ZB, DBPE and Sb2O3was composed of FR program B, two kinds of FRcomplex systems were studied the influence on FR performance of asphalt, thencomparing with the collaborative flame retardant efficiency of nano ZB and ordinaryZB.In order to overcome flow of asphalt in the test process, the paper put forward asample preparation method used to test the flame retardancy, and adopted limitingoxygen index (LOI) to test the flame retardancy of the FR asphalt. In order to determinethe best adding amount of each flame retardant, the autor added each flame retardant in different dosage to the asphalt, compared and analyzed the FR efficiency and FRperformance, therefore determined the optimal dosage range. Then according to theorthogonal experiment method and the three index tests of asphalt, the best proportionand the optimum content of each FR scheme were determined. Rresearch resultsshowed that the optimal proportion of program A was DBPE: Sb2O3: nano ZB=7:2:2,5%optimum content,28.9%LOI; program B was DBPE: Sb2O3: ordinary ZB=7:2:3,8%optimum content,29.2%LOI; collaborative flame retardant efficiency of nano ZBwas better than ordinary ZB; penetration and ductility of FR asphalt decreased,softening point higher.Secondly, the paper verified respectively pavement performance of Matrix asphaltmixture, FR asphalt mixture of plan A, FR asphalt mixture of plan B, through therutting test, low-temperature bending test, retain Marshall test and so on. Test results asfollows: the three schemes were able to meet the standards and requirements of“highway engineering asphalt and asphalt mixture test regulations”(JTJ052-2000); theperformance of plan A FR asphalt mixture was better than FR asphalt mixture of plan B,smaller difference with performance of matrix bituminous mixture.Finally, the paper evaluated combustion performance of asphalt mixture of the threeoptions, by the direct combustion of asphalt mixture test and complete combustion test.The results showed that the FR effect of FR plan A and plan B was significantly betterthan conventional asphalt mixture, and plan A was the best.The mechanism of nanocomposite FR asphalt was discussed, by comparing thermaldecomposition of matrix asphalt and FR asphalt. In300℃~540℃stage, when nano-composite flame retardants happened thermal decomposition, difficult burning gas,gesso, metal oxide and so on were generated, so the concentration of combustible gaswas diluted, heat was reduced, the REDOX reaction and heat oxidative cross-linkingreaction of asphalt were promoted, the mechanism of cooling diluted and catalytic ofnanocomposite FR asphalt was played.