Interaction Mechanism And Performance Investigation Of Crumb Rubber Modified Asphalt With High Content And Asphalt Mixture Based On Graded Activation

Under the goals of carbon peaking and carbon neutrality,the recycling and utilization of solid waste has great significance.Crumb rubber,as an asphalt modifier,can not only delay the consumption of asphalt material to a certain extent,but also bring a great degree of improvement to the performance of asphalt pavement material.However,due to the high viscosity of crumb rubber modified asphalt,poor compatibility and storage stability,the research on content of crumb rubber is mostly concentrated around 15～20%,and it is difficult to continue to improve the content.Based on this,the interaction mechanism and rheological properties of 30%high content rubberized asphalt were studied systematically.In the process of activation of crumb rubber,three methods of crumb rubber activation,pre-swelling activation,microwave irradiation activation and high-temperature activation were studied.A variety of macro and micro analysis methods were used to study the properties of crumb rubber modified asphalt under different activation methods from multiple angles.The compatibility of crumb rubber modified asphalt after pre-swelling activation is the best.It is suggested to improve the compatibility between crumb rubber and asphalt with pre-swelling activation method.The pre-swelling combined with twin-screw extrusion method was used for gradient activation of crumb rubber from waste tire.The orthogonal experiment was used to study the advanced treatment process parameters of crumb rubber.It was found that the degree of influence factors of crumb rubber treatment process from large to small were as follows:extrusion temperature>developmental temperature>extrusion speed>developmental time>extrusion time>aromatics oil content.According to the softening point,viscosity of 135℃,rut factor of 50℃ of modified asphalt with high content of crumb rubber,the 18 types crumb rubber were put in treatment degree order by TOPS IS comprehensive analysis method.Then the crumb rubber treatment degree was divided into "deep zone","middle zone" and "shallow zone" according to the relatedness of TOPSIS analysis and solubility,surface morphology and functional group changes of crumb rubber.It was found that in the soluble fraction of the crumb rubber extracted by toluene,ortho-disubstituted benzene and conjugated double bonds appeared,and S-S bonds,C-S bonds and C=S double bonds realized fractional fracture,which meant that obvious vulcanization degradation occurred,and the structure of crosslinking bond changed,but the vulcanization reversion also occurred.By the combination of micro and macro test,the interaction mechanism between crumb rubber and asphalt was revealed,and the compatibility of high content crumb rubber modified asphalt was explored.It is found that the compatibility of high content crumb rubber modified asphalt increases first and then decreases with the enhancement of treatment degree.When the extrusion temperature was higher than 220℃,the vulcanization reversion phenomenon occurs in the process of crumb rubber treatment,and the higher the treatment degree,the more serious of this phenomenon.In that case,the vulcanization recombination occurred in small molecules,which makes the size of the crumb rubber become larger and the particle effect become stronger.It was also found that the solubility of crumb rubber increased with the increase of treatment degree,and the separation ratio between crumb rubber and asphalt increased.The modified asphalt with recombined high content crumb rubber has certain advantages in compatibility.It not only has the characteristic of increased flexibility and decreased sensitivity of crumb rubber,but also has the characteristic of lower viscosity of crumb rubber.The low viscosity and balanced high and low temperature performance of high content crumb rubber modified asphalt can be achieved with the appropriate recombination ratio.The physical properties,rheological properties and creep properties of high content crumb rubber modified asphalt were studied by softening point,rotational viscosity,temperature sweep,multi-stress creep recovery test,frequency sweep and low temperature bending test.The high temperature rheological property test results showed that compared with SBS modified asphalt,the crumb rubber with 30%～40%solubility has stronger effectiveness and superiority in improving the high temperature deformation resistance of asphalt,and crumb rubber with 40%～60%solubility has more obvious improvement on the low temperature performance of modified asphalt,but the proportion of crumb rubber with 40%～60%solubility should not exceed 55%.Finally,the road performance of the high content crumb rubber modified asphalt mixture was evaluated.It was found that the crumb rubber with 30%～40%solubility modified asphalt had excellent high temperature rutting resistance,low temperature cracking resistance and water damage resistance.Performance of the recombined high content crumb rubber modified asphalt mixture was little different from that of the crumb rubber with 40%～60%solubility modified asphalt mixture.