| In recent years,the application of acid aggregates in bitumen pavements has become a research hotspot.Compared with alkaline and neutral aggregates,acidic aggregates have less engineering applications due to their poor adhesion to bitumen.However,with the development of society and economy,the scale of bitumen pavement is increasing year by year,and the consumption of traditional alkali-neutral aggregate used in the project is also increasing.In the future,it may face the problem of exhaustion of natural high-quality aggregates.The inorganic/organic composite materials has attracted widespread attention because of its superior comprehensive properties.Applying this idea to bitumen modification is expected to develop new green road modified bitumen materials to promote the application of acidic aggregates in highway engineering.In this thesis,3-aminopropyltriethoxysilane(APTES)was used as an organic modifier to organically treat calcium-based montmorillonite(MT),and organic montmorillonite(OMT)was prepared.X-ray diffraction analysis(XRD),Fourier transform infrared spectroscopy(FTIR),differential thermal-thermogravimetric analysis(TG-DSC),scanning electron microscope(SEM-EDS),total organic carbon analyzer(TOC),Zeta electric potential and other characterization methods are used to research the microscopic morphology and structure of OMT;the conventional indexes of OMT modified bitumen(penetration,softening point,ductility,viscosity)have been tested to evaluate the basic performance of OMT bitumen;the adhesion performance of OMT bitumen was evaluated by pulling-off test and water boiling test;the road performance of OMT modified bitumen mixture(high temperature stability,water stability)was studied.The result shows:(1)OMT was prepare by using APTES as an organic modifier to organically modify MT.XRD,FTIR,and TG results show that the surface functionalization of OMT forms an intercalation structure and a grafting structure.The intercalation structure increases the interlayer spacing of the OMT which is beneficial to the loading of bitumen.The grafting structure will make the OMT particles and the bitumen form a stable Si-O-Si/Al-O-Si chemical bond.Both will promote the adhesion and thermal stability between OMT and bitumen.(2)OMT bitumen was prepared by melt intercalation method.The physical performance test shows that after OMT is added to bitumen,it has no obvious effect on the softening point,the penetration decreases and the viscosity increases.With the gradual increase of OMT content,the penetration and ductility of OMT modified bitumen gradually decrease.When the mass content is 1%～3%,the OMT reaches a saturated state,and a stable network structure is formed in the bitumenenes.After that,as the OMT content increases,the plastic change of the bitumen slows down.(3)OMT particles have a positive charge and can form a double-charge layer between the bitumen and the acidic aggregate in a humid environment,thereby enhancing the adhesion between the bitumen and the acidic aggregate.After adding 5.0% OMT,the fracture energy and peak load of the bitumen increased significantly,and the coating degree of the bitumen on the surface of the acidic aggregate was also improved after the boiling test.From the perspective of cost and best performance,the best dosage of OMT modifier is 5.0% of the bitumen mass.At this time,OMT modified bitumen has better adhesion performance than pure bitumen. |
