| With the increase of road traffic volume year by year,the problem of pavement crack becomes more and more prominent.It is important to choose reasonable and efficient crack repair method for road preventive maintenance.3D printing technology,with its intelligent technical characteristics,has broad application prospects in the field of road engineering.Therefore,the research on the pavement crack repair materials used for 3D printing has important practical application value.In view of the problems existing in the commonly used styrene-butadiene-styrene block copolymer(SBS)/waste rubber powder(CR)modified asphalt crack repair materials,such as large viscosity,and insufficient durability and difficulty to be applied for 3D printing.The liquid nitrile butadiene rubber(LNBR)with low viscosity was introduced into the SBS/CR system to prepare SBS/LNBR/CR modified asphalt crack repair material for 3D printing.Specific research contents are as follows:(1)SBS/LNBR/CR modified asphalt was prepared with SBS,LNBR and CR.The effects of asphalt type,LNBR dosage,mesh number and dosage of rubber powder and modification technology on pavement performance of modified asphalt were studied.Softening point,cone penetration,elastic recovery,flow value,storage stability and 180 ℃ viscosity were used as evaluation indexes the formula.The optined formula was 90# asphalt,4% SBS,3% LNBR,22%CR content of 40 mesh.The optimal modification process: SBS,LNBR and CR were added in order with the corresponding shear time.The shear temperature was 190 ℃.The shear rate was5000 r/min.The development time was 1.5 h.(2)The rheological properties and aging resistance of matrix asphalt,SBS modified asphalt,SBS/CR modified asphalt and SBS/LNBR/CR modified asphalt were compared.The dynamic shear rheological test(DSR)was used to evaluate the high temperature rheological properties of materials.The results of temperature scan test,frequency scan test and multiple stress creep test(MSCR)showed that adding SBS/CR was beneficial to the rutting resistance at high temperature.The elastic component of asphalt was furtherly increased by adding LNBR,The deformation recovery rate improved and the non-recoverable creep compliance reduced.The low temperature rheological property of the modified asphalt was evaluated by the bending beam rheological test(BBR).The results showed that the low temperature property was improved by the addition of SBS and CR.The low temperature property of the modified asphalt was improved by addition of LNBR.The heat resistant oxygen aging property of the composite modified asphalt was evaluated by rotating film oven aging test and pressure aging test.It was found that LNBR could obviously improve the heat resistant oxygen aging property of the composite modified asphalt.The light oxygen aging property was evaluated by ultraviolet aging test.The ultraviolet aging property was slightly reduced.(3)The microscopic distribution,modification mechanism and thermal stability of three modifiers in asphalt were studied by fluorescence microscopy,infrared spectroscopy and thermogravimetric analysis.The infrared spectrum results showed that no new bond was found which indirected that the modification was mainly physical mixing.The fluorescence micrograph showed that SBS,LNBR and CR were evenly dispersed in the asphalt.The CR was flocculent and interwoven with granular SBS and LNBR.The SBS、LNBR and CR were coupling linked to form a stable network structure in the asphalt.Thermogravimetric analysis show that the modified asphalt had a good thermal stability.(4)Based on the principle of melt deposition,the printability and constructability of SBS/LNBR/CR composite modified asphalt were studied by plunger 3D printer.The printing parameters were preliminatively explored,including printing temperature,nozzle diameter,extrusion rate,floor temperature and deposition rate.The results showed that the printing temperature decreases significantly after LNBR is added.The extrusion could be carried out continuously and smoothly at 120 ℃.In continuous printing,the repair material can be successfully stacked without fusion and collapse,indicating that SBS/LNBR/CR composite modified asphalt has good 3D printing molding performance.(5)The construction technology of SBS/LNBR/CR composite modified asphalt repair material was studied.The road performance was evaluated by surface drying time,appearance,smoothness,filling depth and water seepage coefficient.The results showed that the crack repair material had the advantages of low heating temperature,large penetration depth and fast drying time.The repaired pavement had high smoothness and cracks do not seep water,which can meet the actual needs of pavement maintenance. |
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