Research On The Performance And Microstructure Of Polyphosphoric Acid Modified Asphalt

With the rapid development of highway construction, the amount of asphalt concrete increases every year in China. So the amount of asphalt is rapid growth.Due to the increase of traffic and load, the matrix asphalt has been difficult to meet the requirements of the road now. A variety of modifiers has been used to improve asphalt performance to meet the needs of the asphalt road. Polymer-modified asphalt which is a physical modification has some disadvantages such as high cost, needing expensive modified equipment, complex modified process and poor storage stability. It restricts the development of modified asphalt. By adding more polyphosphoric acid in the asphalt modification, can effectively solve the disadvantage of the existing physical modification. The phosphoric acid polymer modified asphalt has the advantages of low cost and simple processing technique, so the good promising application can be expected.First to verify the modifying effects of polyphosphoric acid on asphalt of yunnan local used, based on the laboratory preparation of the polyphosphoric acid modified asphalt, the effects of polyphosphoric acid on the matrix asphalt was studied. The test results show that the softening point was increased, and the penetration and ductility were decreased with the introduction of polyphosphoric acid. Polyphosphoric acid can effectively improve the matrix asphalt thermal susceptibility, high temperature stability, aging resistance performance, etc., which has good modification effect of asphalt used in Yunnan.Above on the performance of the polymer modified asphalt phosphate is studied, but this test is using the empirical indicators of specification in our country, so it can not quite accurate to evaluate the performance of the material, and the correlation of actual road performance is poorer.In order to better understand the modification effect of polyphosphoric acid on the matrix asphalt, from the perspective of viscoelastic mechanics, this paper studies the viscoelastic mechanics behavior of the polyphosphoric acid modified asphalt, and tries to set up the relationship of the pavement performance.In this paoer. the effect of the asing before and after polyphosphoric acid modified asphalt on viscoelastic parameters of temperature and load frequency is studied by the dynamic shear rheological experiment.The creep property of the polyphosphoric acid modified asphalt aging before and after were analyzed by static experiments which is multiple stress and creep recovery text.Experimental results show softening point was increased, and the penetration and ductility the plural shear modulus (G*) and the fatigue factor(G*sinδ) were increased,the total strain and the irreversible strain were decreased when the polyphosphoric acid add in the asphalt. So the polyphosphoric acid modified asphalt can enhance the ability of the resistance to permanent deformation in the pavement. the polyphosphoric acid modified asphalt can reduce the sensitivity of the load and the influence of the aging of asphalt, so it can improve the fatigue resistance and durability.The change of the material macroscopic properties has a close relationship with microscopic structure. Studying the change of the material microstructure has important significance in understanding the structure-activity relationship of material,and to establish a link between macro to micro scale.In this paper, in order to study the micro influence of polyphosphoric acid on asphalt, the phase diagram, topography and force-displacement curve of before and after the aging of the polymer modified asphalt is studied by atomic force microscope.Results show that the atomic force microscope is a powerful tool to study the micro structure of the asphalt. When the polyphosphoric acid adds in the asphalt, the "bee" structure is increased and mutual connection to grow up, and the white area is increase. When the polyphosphoric acid adds in the asphalt, the modulus of elasticity is decreased, and the adhesion strength is increases in the white area.Summary, polyphosphoric acid as a chemical modifier, not only can be used alone to well improve the performance of asphalt, also can be compounded with other polymers to produce more excellent performance of modified asphalt to meet the requirements of high-performance road. The microscopic morphology of the asphalt can be well observed, and the mechanical properties can be tested under the micro by atomic force microscopy. It is the foundation to study of the relationship between microcosmic properties and macroscopic properties for the future.