| As an important food production base in China,the northeast region has abundant reserves of biomass materials such as crop straw,but the utilization rate is low,and most of them are disposed of by burning,which not only wastes resources but also pollutes the environment.At present,there are many researches to prepare agricultural waste into bio-asphalt by physicochemical treatment and apply it to road construction,which minimizes the environmental pollution caused by the treatment of agricultural waste and also further improves the utilization rate of resources,which is beneficial to the green and sustainable development of resources.Bioasphalt is a product prepared by mixing bio-oil extracted from biomass materials with asphalt under certain conditions,which has the characteristics of environmental protection,abundant reserves and low price,and has attracted the attention of many researchers.However,the current technology of bio-asphalt is still immature,and there are a series of problems such as unclear refining process of pyrolysis products,high temperature sensitivity and easy aging,which limit the application of bio-asphalt in road materials.Based on this,this paper explores the effect of purification treatment on the performance of asphalt with agricultural residues as raw materials,the process conditions of solvent liquefaction of straw and the performance of bio-asphalt,and the use of agricultural residues to prepare epoxy asphalt with better high temperature performance to make up for the defects of bio-asphalt.The specific research work in this paper is as follows:(1)Although there are many studies on the pyrolysis of agricultural waste,there are few reports on the treatment and preparation of bio-asphalt from its pyrolysis products.In this chapter,the degradation products of corn stover were obtained by high-temperature pyrolysis,and then mixed into asphalt to prepare bio-asphalt after different degrees of purification: one is to use the direct product of corn stover pyrolysis(CSC)to prepare bio-asphalt,and the other is to prepare bio-asphaltbio-asphalt by purifying the direct product of corn stover pyrolysis(CST).Compared with CST,the naked eye can see that CSC contains a large number of fine black particles inside;in addition,we found that the purified CST has more specific gravity of alkanes and phenols,similar to the composition of matrix asphalt,flatter apparent phase and better thermal stability by means of Fourier infrared spectroscopy,gas chromatography mass spectrometry,scanning electron microscopy and thermogravimetry;further analysis of the components revealed that The bio-asphalt(CSTA)prepared from CST has more asphaltene and less gum,and has a more stable colloidal structure and better high temperature performance.These studies showed that the direct product of pyrolysis affects the low temperature performance of asphalt,and CSTA6 meets the requirements of 90# asphalt for road use.(2)In this study,the effects of temperature,retention time,ratio of liquefying agent,content of catalyst,and liquid-solid ratio on the liquefaction rate were investigated using rice straw as raw material,polyethylene glycol 400(PEG400)and propanetriol as solvents,and ptoluenesulfonic acid as catalyst by the univariate method.It was found that the liquefaction rate reached the highest value when the temperature was 180 ℃,the retention time was 3 h,the liquid-solid ratio was 3.5:1,the ratio of liquefying agent was 1.5:1,and the ratio of catalyst was45%.The liquefaction products were purified to obtain bio-oil(RSB),which was blended into asphalt to finally obtain bio-asphalt(RSBA).Through Fourier infrared spectroscopy and thermogravimetric test,it was found that the bio-oil contains more oxygen-containing functional groups and has better thermal stability than CST.Through needle penetration,softening point,DSC,adhesion test and DSR test,it was found that the addition of RSB makes the asphalt needle penetration decrease first and then increase,softening point increase,glass transition temperature decrease and rutting resistance increase.Combined with the classification standard of road asphalt,RSBA20 meets the use standard of 90# asphalt and can be used in the alpine region of northeast China.(3)Conventional epoxy asphalt is a kind of modified asphalt prepared by curing epoxy resin as a framework for high temperature resistance.In this study,using the construction of epoxy system,lignin is used as the basic raw material,and the dynamic covalent bonding unique to the vitrimer system is added to the system of epoxy asphalt to construct a dynamic reversible epoxy asphalt.The lignin epoxy resin,lignin carboxylate as curing agent,and zinc acetate catalyst were added to the asphalt to obtain ELEA,which has good high temperature performance and mechanical strength(tensile strength 1.605 MPa,elongation at break 382.38%)in accordance with the requirements of epoxy asphalt for steel bridge deck pavement mixes.The characterization of ELEA viscosity,thermal properties and high-temperature reversibility showed that ELEA has good operability,thermal stability and potential for recovery and recycling.In this paper,it is found that after pure treatment,the bio-oil has better compatibility with asphalt,and its low temperature performance is more in line with the conditions of road use.The technology of straw liquefaction was explored,and the liquefaction product was purified to prepare bio-asphalt.Epoxy asphalt prepared from lignin has good high temperature performance,and the addition of dynamic covalent bond makes it reversible at high temperature.From purification treatment to raw material preparation to performance improvement,the integrated preparation process from agricultural residues to bio-asphalt was established. |
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