| In recent years,the proportion and scale of tunnels in my country’s highway construction have become larger and larger,and most of them appear in the form of tunnel groups and super-long tunnels.For tunnel asphalt pavement,on the one hand,the mixing temperature of traditional hot-mix asphalt mixture is high,and the large amount of smoke released during the construction process not only seriously harms the physical and mental health of the constructors,but also directly affects the construction quality;on the other hand,the asphalt itself Its flammability and its inadequate combustion in tunnel traffic accidents release a large amount of dense smoke,which directly threatens the safe operation of highway tunnels,especially super-long tunnels.Therefore,the paving of extra-long highway tunnels puts forward higher requirements on the flame retardant and smoke suppression performance,mixing temperature and road performance of asphalt and asphalt mixtures.From the perspective of construction and operation of extra-long tunnel pavement,this paper prepares a warm-mix flame-retardant asphalt with excellent flame-retardant and smoke-suppressing properties and significantly lower mixing and compaction temperature to meet the requirements of extra-long tunnel pavement.(1)Preparation of asphalt flame retardant based on surface modification and warm-mix flame-retardant asphalt.First,use titanate coupling agent and silane coupling agent to modify the surface of intermediate MZ(a combination of magnesium hydroxide flame retardant and zinc borate in a certain proportion)to prepare new flame retardants MZ-Ti and MZ-Si.Secondly,the optimal preparation process of warm-mix flame-retardant asphalt was determined through orthogonal experiment,and then the optimal content of warm-mix agent and flame-retardant in warm-mix flame-retardant asphalt was determined,and MZ-Ti warm-mix flame-retardant asphalt was prepared.And MZ-Si warm-mix flame-retardant asphalt.(2)Test and evaluation of flame-retardant and smoke-suppressing performance of warm-mixed flame-retardant asphalt.In this paper,SBS modified asphalt is used as raw material,and Rediset~?LQ1102 warm mix agent,MZ-Ti and MZ-Si flame retardants are used as modifiers to prepare five modified asphalts,namely MZ-Si flame-retardant asphalt and MZ-Si warm-mix flame-retardant asphalt,MZ-Ti flame-retardant asphalt,MZ-Ti warm-mix flame-retardant asphalt and warm-mix SBS modified asphalt.Through limiting oxygen index test and smoke density test,the flame retardant and smoke suppression properties of six asphalts were tested and comparatively analyzed,and their thermal decomposition properties were studied through thermogravimetric analysis test.The results show that the limiting oxygen index LOI of MZ-Ti warm-mix flame-retardant asphalt and MZ-Si warm-mix flame-retardant asphalt are 27%and 26%,respectively,and the maximum smoke density is 55.5%and 56.2%,respectively.Both flame retardant and smoke suppressive Better performance;compared with SBS modified asphalt,the mass loss rate M_p,the final residual carbon content M_f,and the temperature T_p corresponding to the maximum mass loss rate of the two warm-mix flame-retardant asphalts have changed significantly,and both Shows its good flame retardant properties.(3)Research on the road performance of warm-mix flame-retardant asphalt.In this paper,the conventional performance and Brookfield viscosity of the above six asphalts were tested respectively,and then the rheological properties before and after short-term aging and long-term pressure aging were compared and analyzed,and their anti-aging performance was evaluated.The results show that Rediset~?LQ1102 warm mixing agent has a significant cooling effect,effectively reducing the mixing temperature of modified asphalt;after short-term and long-term aging,the residual penetration ratio,mass loss,complex modulus and phase of the six asphalts The change of the angle indicates that the blending of MZ-Ti and MZ-Si flame retardants has an adverse effect on the anti-aging performance of asphalt,but the incorporation of warm mixing agent can improve the anti-aging performance of asphalt to a certain extent.(4)Study on the storage stability of warm-mix flame-retardant asphalt.By comparing the test methods,the segregation test was used to test the softening point changes of the upper and lower asphalts of MZ-Ti warm-mix flame-retardant asphalt and MZ warm-mix flame-retardant asphalt after different storage time.The storage stability of the flame retardant was evaluated;on this basis,infrared spectroscopy tests were carried out on the upper and lower asphalts before and after the separation of the two flame-retardant modified asphalts.The area changes of the characteristic functional groups of the flame retardants were quantitatively calculated by the ORIGIN software.Angle analyzed and evaluated its storage stability.The results show that the softening point difference between the upper and lower parts of the MZ-Ti warm-mix flame-retardant asphalt after different segregation times is significantly smaller than that of the corresponding MZ warm-mix flame-retardant asphalt;MZ-Ti warm-mix flame-retardant asphalt After different segregation times,the peak area S of the absorption peaks of hydroxyl-OH and saturated hydrocarbon C-H at the upper and lower parts and the area difference△S at different time periods are all smaller than the peak area of the corresponding MZ warm-mix flame-retardant asphalt,indicating that the titanate couple The linking agent can improve the connection between the flame retardant and the asphalt interface,so that the flame retardant can better combine with the modified asphalt,and significantly improve the storage stability of the MZ-Ti warm-mix flame-retardant asphalt.(5)Research on the performance of warm-mix flame-retardant asphalt mixture.This paper selects AC-13I synthetic gradation to design the mixture composition,selects basalt as the aggregate,and uses SBS modified asphalt,warm mix SBS modified asphalt,and MZ-Ti warm mix flame retardant asphalt to prepare three asphalt mixtures.The flame retardant properties of the three asphalt mixtures are studied through the burning time,flame size and dynamic stability of the rut plate after burning through the rut plate burning test,and then the road performance of the mixture is evaluated.The results show that the warm-mix flame-retardant asphalt mixture has excellent high-temperature stability,the best flame-retardant effect,and other properties meet the requirements of the specification.In general,MZ-Ti warm-mix flame-retardant asphalt is suitable for paving super-long tunnel pavement. |
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