Preparation And Property Evaluation Of Polymer Modified Asphalts Used As Stress Absorbing Membrane

Semi-rigid base is used widely at high grade asphalt pavement in our country because of its higher compression strength,integrity and bending strength,but semi-rigid base give birth to reflection cracks easily.The development of reflection cracks will induce a series of problems which appear on pavement and shorten the service life of road.At present,preventing and mitigating reflection cracks become the important task on the development of road.This paper takes preventing and mitigating reflection cracks as a point of departure.In the first place,an evaluation system about polymer modified bitumen as stress absorbing materials is brought forward on the base of that a lot of information is consulted and analyzed.Secondly,rubber-modified asphalt and SBS modified asphalt which is used as stress absorbing materials are prepared.The physical properties,mechanical properties and operation properties are studied. Microstructure of material is studied by fluorescence microscopy.At the end,aging properties of the two types of materials is compared and analyzed.An evaluation system about polymer modified bitumen as stress absorbing materials is put forward on the base of research in this paper,stress absorbing materials are evaluated from the following 4 aspects:physical properties,mechanical properties of the stress,absorbing materials,mechanical properties of the stress absorbing interlayer and operating properties of the stress absorbing materials.The technology of making rubber modified asphalt is studied.The result shows that the optimal technology is that rubber and asphalt is mixed under 215℃until 2.5 hour.Fluorescence microscopy analyzes show that a part of rubber particle swells incompletely when temperature is 190℃;The interface of rubber particle is misty and asphalt is filled in the gap of rubber when temperature is 220℃,which shows that rubber swells completely and form network;when temperature is 240℃,rubber swells completely,but single rubber separates and is not a whole.Therefore,the properties of asphalt descend rapidly.The study of changing rubber proportion shows that 22%is reasonable. Studies of SBS modified asphalt have found that the properties of modified asphalt are the best when stabilizer is 0.13%and MAH is 0.3%.Fluorescence microscopy analyzes show that applied MAH to crosslink SBS molecule form network which improve physical properties and mechanical properties of SBS modified asphalt.The aging properties of two types of modified asphalt are studied by the Thin Film Oven Test(TFOT)and accelerated thermal oxidative aging.The results showed that two types of modified asphalt have good resistance to thermal oxidative aging. Compared with SBS modified asphalt,rubber modified asphalt have lower rate of change of viscosity,higher rate of reserve of tensile strength,adhesive strength and shear strength.