Research And Application Of Asphalt Mixture Produced In Half-Warm Mix Asphalt Technology With Emulsified

Asphalt pavement occupies a large proportion in pavement engineering with excellent performance,but the high production and construction temperature leads to a large amount of energy consumption and harmful gas emissions,which has become an urgent problem to be solved,especially in the context of the country ’s vigorous promotion of the " double carbon " goal.Half-warm mix asphalt technology has attracted much attention because it can greatly reduce production temperature and does not change road performance.At present,the binder of half-warm mix technology mainly adopts foamed asphalt or traditional emulsified asphalt,but the former has poor adhesion and insufficient bonding force,which can only be used for lowlevel pavement,while the latter has high residual water content,resulting in long strength formation time of mixture and low road performance.Therefore,there is an urgent need to develop new high-performance binders to improve the road performance of half-warm mix asphalt.Based on the theory of abrupt phase transition,according to the preparation process of high internal phase emulsion,high internal phase asphalt emulsions was prepared as the binder of half-warm mix asphalt mixture,and its preparation process,rheological properties,workability and road performance of the mixture were studied.The main contents are as follows :The preparation process of high internal phase asphalt emulsions was investigated by conductivity test,dispersion test,particle size analysis,storage stability analysis and evaporation residue performance analysis.The results show that with the increase of stirring time,the particle size distribution of high internal phase asphalt emulsions decreases gradually,and the emulsification effect becomes better.The suitable stirring time is 10 min.With the increase of asphalt content,the particle size distribution of high internal phase asphalt emulsions decreases,the storage stability first increases and then decreases,and the performance of evaporation residue changes slightly.Among them,the maximum asphalt content of high internal phase asphalt emulsions is 96 %.With the increase of emulsifier content,the particle size distribution of high internal phase asphalt emulsions gradually decreases,the storage stability gradually increases,the performance of evaporation residue changes slightly,the penetration increases,the softening point decreases,and the ductility increases.With the increase of stirring rate,the particle size distribution of high internal phase asphalt emulsions gradually decreases,the storage stability gradually increases,and the performance of evaporation residue only changes slightly.In addition,the orthogonal test was further used to determine that the asphalt content had the greatest influence on the emulsification effect of high internal phase asphalt emulsions,and the optimal preparation conditions of high internal phase asphalt emulsions were determined as follows : asphalt content was 89 %,emulsifier content was 4 %,and stirring rate was 1000 rpm.The rheological properties of high internal phase asphalt emulsions were studied by rheological research method,and the viscoelastic properties and flow model of high internal phase asphalt emulsions were determined.The results show that the viscoelastic properties of high internal phase asphalt emulsions change with temperature,and there is a ’ gel point ’ of viscoelastic transformation.The temperature corresponding to the ’ gel point ’ gradually increases with the increase of asphalt content.When the droplet size is monodisperse,the temperature corresponding to the ’ gel point ’ has no significant change with the particle size.When the droplet size is polydisperse,the ’ gel point ’ does not appear within 100 ℃.The complex viscosity(|η*|)curve of high internal phase asphalt emulsions was fitted by Arrhenius equation to obtain the viscous flow activation energy △E,which was used to quantitatively characterize its temperature dependence.With the increase of asphalt content or the decrease of droplet size,△ E gradually increases,showing a stronger temperature dependence.The viscosity curve and stress curve of high internal phase asphalt emulsions were fitted by Carreaun-Yasuda and Herschel-Bulkley equations.The results showed that the high internal phase asphalt emulsions was pseudoplastic fluid after the ’ gel point ’,and there was yield stress.With the increase of asphalt content or the decrease of droplet size,the pseudoplasticity and yield stress of high internal phase asphalt emulsions gradually increase.The amplitude scanning results show that there is a linear viscoelastic region after the ’ gel point’ of high internal phase asphalt emulsions.With the increase of asphalt content or the decrease of droplet size,the linear viscoelastic region of high internal phase asphalt emulsions gradually increases,and the storage modulus G ’ value gradually increases.The frequency scanning results show that the modulus of high internal phase asphalt emulsions changes little in a wide angular frequency range,showing good storage stability.The workability of high internal phase asphalt emulsions as the binder of half-warm mix mixture in the process of mixing and compaction and the time of subsequent strength formation were studied.The results show that the recommended mixing process of half-warm mix asphalt mixture is as follows : the aggregate and high internal phase asphalt emulsions are mixed evenly and then mixed with mineral powder.According to the volume parameters and road performance evaluation of half-warm mix asphalt mixture,the optimum asphalt content of high internal phase asphalt emulsions is 86 %.It is determined that the asphalt use temperature is 60 ℃ and the mixing temperature is 100 ℃ during the mixing process of the mixture.The longest storage time of the mixture from mixing to compaction is 8 hours.The early strength of the mixture after molding meets the requirements of the specification.After 7 days of curing at room temperature,it can reach stable strength and has good workability.The pavement performance of half-warm mix asphalt mixture based on high internal phase asphalt emulsions was studied,and compared with hot mix asphalt mixture and warm mix asphalt mixture.The results show that the road performance of high internal phase asphalt emulsions meets the requirements of hot mix asphalt mixture in the specification.Among them,the high temperature performance is similar to that of hot mix and warm mix asphalt mixture,and the low temperature performance is better than that of hot mix asphalt mixture,slightly worse than that of warm mix asphalt mixture.Water stability : residual stability is better than hot mix and warm mix asphalt mixture,and freeze-thaw splitting strength ratio is lower than hot mix and warm mix asphalt mixture.In addition,the fatigue performance of half-warm asphalt mixture was investigated by four-point bending fatigue test.The results show that the half-warm asphalt mixture has better fatigue performance.At the large strain level(strain ≥ 600 με),its fatigue life decline rate is lower than that of hot mix asphalt mixture and warm mix asphalt mixture,showing better fatigue performance.