Study on properties of foamed asphalt cold recycled mixture under low temperature environment in cold regions
According to the climatic characteristics of Xizang,Qinghai and other provinces in China,the cli-mate is cold throughout the year,the average temperature is low,the temperature difference between day and night and the annual temperature difference is large,and the freeze-thaw cycle is frequent,the field curing condi-tions of foamed asphalt cold recycled mixture under low temperature,room temperature,medium and high tem-perature were simulated at 5℃,10℃,22℃,40℃,60℃ and 110℃,respectively.Based on the differences of indoor mechanical properties(unconfined compressive strength,dynamic resilience modulus),road perfor-mance(high temperature rutting test,OT anti-reflection crack test,immersion Marshall and freeze-thaw split-ting test)and fatigue performance(indirect tensile fatigue test),the effects of low ambient temperature in cold regions on the deterioration of mechanical properties,road performance and durability of foamed asphalt cold re-cycled were analyzed.Based on digital image processing technology and industrial CT non-destructive testing technology,the influence of curing temperature on the dispersion properties and micro-pore structure of foamed asphalt cold recycled mixture was discussed.The results show that the mechanical indexes such as uniaxial pene-tration strength,unconfined compressive strength and dynamic resilience modulus increase exponentially with the increase of curing temperature.Compared with the standard curing condition,the high temperature stability,anti-reflective crack performance and anti-fatigue performance of foamed asphalt cold recycled mixture mixed and cured at low temperature decreased significantly,and the lower the ambient temperature,the greater the re-duction amplitude of the comprehensive road performance of foamed asphalt cold recycled mixture.When the curing temperature was increased,the dispersion area of foamed asphalt at the fracture interface increased,and the diameter of micro-void decreased,and the proportion of void less than 0.05 mm3 in micro-void structure in-creased.The mechanism of the effect of curing temperature on foamed asphalt cold recycled mixture mainly lies in the promotion effect of increasing curing temperature on the dispersion properties of foamed asphalt and the thinning effect of micro-void structure.It is suggested that the temperature control should be strengthened during construction and curing care during the construction of foamed asphalt cold recycled mixture pavement,and it is necessary to adjust the indoor mix ratio design curing temperature according to the construction season tempera-ture in cold regions.Research results provide a reference for the popularization and application of foamed as-phalt cold regeneration technology in cold regions.
pavement engineeringfoamed asphalt cold recycled mixturelow temperature environment in cold regionscuring temperaturemechanical propertiesroad performancedispersion properties of foamed asphaltmicroscopic void structure
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