Study On Experimental Factors Of Limited Oxygen Index To Test Combustion Properties Of Asphalt

As asphalt concrete pavement becomes the main pavement in the tunnel, and theflammability of asphalt, the study about asphalt flame retardant properties has been paidmore and more attention. It is critical to evaluate the combustion properties offlame-retardant asphalt accurately and reasonably. Refering to standards in chemicalindustry, the method of limit oxygen index is widely used to test combustion propertiesof asphalt. Therefore, the study about the experimental factors how to influence theresults of asphalt LOI is very important practical significance for an accurateassessment of combustion properties of asphalt.At first, this paper introduces the research status of the combustion properties ofasphalt, limit oxygen index, and combustion properties of asphalt tested by limit oxygenindex. And the questions which still exist in the field of combustion properties ofasphalt tested by limit oxygen index are also analyzed.Secondly, by using limit oxygen index method to test the properties of asphalt,SBS modified asphalt and flame-retardant asphalt, this paper studied and analyzed theaffection of supporting material and mixed flow gas （speed） to combustion properies ofasphalt. The result shows that:（1） Supporting material has a little influence on the resultof asphalt combustion properties. And glass wool, as supporting material, is better thancotton and polyester felt, because glass wool can adsorb more asphalt and protectasphalt from tickling and dipping.（2） According to ASTM D2863-77, when the mixedgas flow rate was be controlled in30⁵0mm/s, the influence of the mixed gas flow onthe result of asphalt combustion properties is micro and negligible.Thirdly, the effect of oxygen concentration, the mixed gas flow and the intialtemprature of asphalt on asphalt combustion properties was simulated using fluentsoftware. The numerical results show that:（1） The greater the oxygen concentration, thegreater velocity in the velocity fields, the higher temperature in temperature fields, andthe faster burning rate of asphalt, the greater consumption rate of O2as well as thegreater generate rate of CO₂and H₂O.（2） Asphalt can burn if it has sufficient initialtemperatureT’₀. WhenT₀＜T’₀, the probability of asphalt burning is little. WhenT₀＞T’₀, asphalt can burn and the initial temperature has little effect on asphaltcombustion. Therefore, it is inferred that the ignition time could be controled reasonablyin order to measure asphalt combustion properties more accurately when using limit oxygen index to test asphalt combustion properties.（3） When the mixed gas flow ratewas controlled in30⁵0mm/s, the mixed gas flow rate has little effect on the asphaltburning performance. Therefore, the results of numerical simulation analyze proved thatthe mixed gas flow rate could be controlled in the30⁵0mm/s, according to ASTMD2863-77.Finally, the research results are summarized. And further research direction aboutthe study on test methods of the limited oxygen index for Combustion Properties ofAsphalt is provided using the above empirical findings.