| Asphalt is flammable,once ignited in tunnel,the consequences will be unimaginable.Therefore,how to improve the flame retardant performance of asphalt has been focused by researchers.At present,adding flame retardant to asphalt is the main method to improve the flame retardancy of asphalt.The commonly used asphalt flame retardants are halogen series,phosphorus series,inorganic hydroxides,etc.Despite the high flame retardant efficiency of halogen and phosphorus systems,there are many problems,such as high smoke emission and high toxicity of products.Although inorganic hydroxide flame retardants will not produce toxic products during volatile flame retardant action,and can inhibit the generation of smoke,their flame retardant efficiency is low.Therefore,the development of environmentally friendly flame retardants with non-toxic,smoke suppression,high flame retardant efficiency has become an urgent problem to be solved in the preparation of flame retardant asphalt.In this paper,TG-DSC,FTIR technologies were adopted to study the mass change,heat generation and flue gas release rules during pyrolysis combustion of SBS modified asphalt.The results showed that the mass loss and heat release of SBS modified asphalt;the mass loss of stage was largest,which focuses on ? the pyrolysis combustion of saturates,aromatics;Phase ? heat release most,which was caused by the pyrolysis combustion of resins and asphaltenes;the important sources of toxicity in asphalt were aldehydes,CO,and other components.Secondly,Aluminum Hydroxide(ATH),Magnesium Hydroxide(MH)and Layered Double Hydroxide(LDHs)were selected as flame retardants to modify SBS modified asphalt with different ratios,and the flame retardant properties and rheological properties of asphalt were studied.The results showed that the oxygen index of modified asphalt could reach 26% only when the content of ATH,MH and LDHs wass 25%,and the content of composite flame retardant was only 20%,which indicated that there was a synergistic flame retardant effect between ATH,MH and LDHs,and the flame retardant capacity of flame retardant was ATH/MH/LDHs>ATH/MH>MH/LDHs>ATH/LDHs>MH/LDHs>LDHs>ATH.Flame retardant can improve the high temperature performance of asphalt.Then,TG-DSC-MS technology was used to study the pyrolysis combustion process of flame retardant modified asphalts.Combined with XRD and SEM technology,the flame retardant mechanism and synergistic mechanism of different inorganic hydroxide flame retardant in asphalt were discussed.The results showed that the influence of flame retardant on asphalt pyrolysis combustion process was related to its pyrolysis characteristics;ATH and LDHs mainly acted in stage and ? ?,and MH mainly worked in and ? ?;the more orderly the carbon layer was,the more obvious the lamellar structure was,which indicated that the better the flame retardant effect of the flame retardant agent was;the composite flame retardant had a wide range of temperature and could inhibit the pyrolysis and combustion of asphalt for a long time;the composite flame retardant also could promote the formation of carbon layer earlier,and the solid phase flame retardant effect was better;therefore,the pyrolysis combustion rate and the heat produced were decreased.Finaly,asphalt mixture was prepared by using flame retardant agent instead of some mineral powder,and the road performance and flame retardant performance of the modified flame retardant mixture were studied.The results showed that the addition of flame retardant could affect the road performance of asphalt mixture to a certain extent,but the performance indexes meet the requirements of the specification;moreover,the residual Marshall stability ratio of flame retardant asphalt mixture after combustion test was significantly higher than that of ordinary asphalt mixture,which indicated that flame retardant could effectively improve the flame retardant performance of asphalt mixture,of which ATH/MH/LDHs composite flame retardant had the best effects. |
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