Study On Crack Resistance Of SMA-5 Asphalt Mixture For Joint

As the mileage of highway and city tunnel is increasing,the damage caused by joint of tunnel pavement is becoming more and more serious.It is one of the key measures to improve the durability of tunnel pavement structure to improve the anti-cracking performance of asphalt mixture used for joint filler,especially the anti-cracking performance at low temperature.The aim of this article is to explore the effect of hybrid modified asphalt on low temperature cracking resistance of asphalt mixture,optimize the design of low temperature crack resistance of SMA-5 asphalt mixture,and improve the cracking resistance of asphalt mixture used for tunnel joints.Firstly,the hybrid modified asphalt was prepared by adding rubber powder and nano zinc oxide into SBS modified asphalt binders,respectively,and its macroscopic properties were studied,including three indexes,rotational viscosity,low temperature creep and high temperature rheological properties.In addition,Fourier Transform Infrared spectrometer(FTIR),Atomic Force Microscopy(AFM)and other microscopic testing methods were used to analyze the anti-aging properties,microstructure and mechanical properties.Secondly,a hybrid modified SMA-5 asphalt mixture was designed,and its cracking resistance at low temperature was comprehensively evaluated by different methods,including confined Thermal Stress Restrained Specimen Test(TSRST),bending beam test,low temperature fracturing test and dynamic indirect tensile rebound modulus test.The cracking resistance performance at low temperature of CRM/SBS and zno nanoparticles /SBS co-modified asphalt of SMA-5 mixtures with different dosage was studied to determine the best formula of CRM and nano zinc oxide to meet the needs of anti-crack at the joints of tunnel pavement.At last,based on grey relational analysis theory to establish the fitting equation to comprehensively evaluate the cracking resistance index at low temperature of SMA-5 mixture,and the reference value of low temperature cracking resistance index was put forward.The following conclusions are made based on the research:1)The macro and micro properties of CRM/SBS and zno nanoparticles /SBS co-modified asphalt are improved with the increase of the addition of CRM and nano zinc oxide.The pre-treated nano zinc oxide can improve the compatibility with SBS modified asphalt,so the performance is better than the untreated nano zinc oxide /SBS hybrid modified asphalt.2)The design of SMA-5 asphalt mixture due to the small maximum nominal particle size,the optimal amount of asphalt is determined to be 6.7%,and its aggregate structure advantage,enhance cracking resistance at low temperature of asphalt mixture greatly.3)Thermal stress restrained specimen test,bending beam test,low temperature splitting test and dynamic indirect tensile rebound modulus test all show that CRM and nano zinc oxide can improve the cracking resistance at low temperature of asphalt mixture,which is beneficial to delay the temperature shrinkage cracking at the joints.The optimal dosage of CRM and nano zinc oxide is 15% and 6% respectively.4)The correlation degree between the freezing fracture temperature and the turning point temperature is above 0.7,the correlation degree between the freezing fracture temperature and the bending strain at 10℃ is above 0.8,and the correlation degree between the freezing fracture temperature and the strength modulus of asphalt at-12℃ is above 0.9,indicating that the evaluation results of these three indexes on the low temperature cracking resistance of SMA-5 asphalt mixture are consistent with the results of freezing fracture temperature.