| Many asphalt pavements in China have entered into the maintenance and repair stage.Reclaimed Asphalt Pavement(RAP).As the main product of asphalt pavement maintenance and milling,it has the problems of wasting land resources and polluting the environment.The application of RAP material in the road subgrade can alleviate the shortage of land resources and road construction sand and gravel resources.But the surface of RAP material coated with asphalt is more difficult to be cemented than ordinary aggregates.So it is necessary to increase the amount of stabilizing materials.Cement is a good stabilizing material for semi-rigid subgrade.But increasing the amount of cement to stabilize RAP material increases the project cost on the one hand,and increases the demand for cement on the other hand,which increases the carbon emission of cement production.The use of inexpensive industrial solid waste output powder to prepare cementitious materials to replace cement clinker.And applying it together with RAP material in road subgrade is of great significance for sustainable development.Based on this,this study adopts the simple shape center of gravity design theory to analyze the performance of cementitious sand under different composition ratios of multi-solid waste cementitious materials.And investigate the importance degree of each component of cementitious materials on the performance of cementitious sand.The sieving test is used for the recovered RAP material to analyze the absence and variability of particle size in each grade of RAP material.Taking the characteristics of solid waste raw materials into consideration,the mix ratio design was carried out for the multi-solid waste stabilized asphalt pavement used materials.And the physical and mechanical properties of the mix were studied by analyzing the mixing rate of solid waste,the particle size of RAP material admixture,the molding and maintenance methods and the ageing period,and the strength variation law and the reasons were investigated.Based on the statistics and analysis of the test data,a prediction model of the effect of aggregate crushing in the mix on the mechanical properties of the mix was constructed.And the main conclusions were as follows:(1)Under the effect of low dosing of desulfurization gypsum,the steel slag powder contributes to the early compressive strength of the colluvial sand.And the influence of mineral powder on the strength is gradually significant with the growth of age.Solid waste-based colluvial sand,the strength formation is slower.And the mechanical prediction model under the age of 56d is more effective.The compressive and flexural strengths of the mastic sand and the brittleness coefficient were integrated.And the planning solution was carried out by Design-Expert to determine the ratio of multi-solid waste mastic materials as,steel slag powder:fly ash:mineral powder:desulfurization gypsum=14.5:62:20:3.5.At this time,the compressive strength of the mastic sand was 17.3 MPa and the flexural strength was4.3 MPa.(2)The maximum dry density and optimum moisture content of the cold recycled mixture of multi-solid waste are negatively correlated with the amount of RAP material admixture and positively correlated with the amount of cementitious material.The mechanical properties of the cold recycled mixture decreased with the increase of RAP material dosing,and the influence of each grade on the cold recycled mixture under the same RAP material dosing was different in significance,among which the most significant influence on the unconfined compressive strength and splitting strength of the cold recycled mixture was 19 mm and 9.5mm sieve.It is recommended that 8%of solid waste cementitious material and 40%of RAP material should be used for the preparation of multi-solid waste cold recycled mix,and the 7d unconfined compressive strength of cold recycled mix is 3.17MPa and 7d splitting strength is0.21MPa.(3)Taking dry density as the preferred reference index of vibration molding parameters,the best parameters of vibration molding were determined as follows:excitation force of6900N,vibration frequency of 30Hz,static surface pressure of 1760N and eccentric block angle of 30°.Compared with static compression molding,the denseness and mechanical properties of cold recycled mixes under vibration molding were better.The dry density of the mixture of vibration molding and hydrostatic molding was significantly different when the amount of RAP material was more than 40%.Compared with hydrostatic molding,vibration molding had less influence on the damage of cold recycled mixture gradation.(4)The way of regeneration on the mechanical properties of the cold in the raw mix has a greater impact.The compressive strength of the cold recycled mixture at 7-28d was higher than that of the control group at 20°C.For the cement cold recycled mixture,the effect of high temperature maintenance on the compressive strength of the cold recycled mixture was more significant.The unconfined compressive strength of cold recycled cement mixes was higher than that of the same RAP material.The prediction model of the influence of four factors,namely RAP dosing,age of curing,type of cementitious material and curing method,on the unconfined compressive strength of cold recycled mixes was constructed by using multivariate nonlinear mathematical model,and the R~2 was 0.81.The prediction of the unconfined compressive strength of cold recycled mixes by this model was highly reasonable. |
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