| Aging of pavement materials is a major problem for high-grades road in China,which is manifested as the decline of anti-skid performance for surface layer and the fading of durability for pavement materials.Thus,the maintenance demands are focused on the functional restoration for road surface and the structural adjustment of the pavement.The porous asphalt thin overlay(PATO)is an ideal choice to meet requirements above,and rubber asphalt is the suitable binder for PATO considering its advantages in terms of durability,high temperature adhesion and economic benefits.Based on constraints in application of PATO,the optimization for PATO materials design and performance evaluation were carried out through indoor test research,finite element simulation as well as test section laying.Firstly,the asphalt binder suitable for PATO was selected from five typical rubber asphalt products,including two rubber powder modified asphalts and three composite modified rubber asphalts,determined by the investigation of current rubber asphalt technology.The three major indexes,elastic recovery,dynamic viscosity at 60℃,viscosity-temperature curve,and PG classification related parameters were obtained.Considering the overall performance,construction process requirements and maintenance costs,SRC-A of the composite modification group was chosen as the suitable asphalt binder.Secondly,the mix design for PA13/10 gradation was conducted.PA13-J was designed with good skeleton stability,and the design oil-rock ratio was 4.9%.For the PA10 with relatively diverse features,the gradation design was carried out based on the coarse relationship among three specifications.The dynamic stability of the asphalt mixture was selected to reflect the skeleton stability of gradation.PA10-S was selected as the optimal gradation for its best skeleton stability,and the design oil-rock ratio was 5.7%.Based on the gradation design results,the applicability of two criterions for PA13/PA10 skeleton design was verified,including the SMA skeleton judgment criterion and the primary structure formation criterion.It is reflected that the former criterion is greatly affected by test deviation and the judgment results are not accurate.The latter criterion based on the packing theory confirms the main particle size range of the PA13/10 skeleton structure,that is,9.5～13.2&4.75～9.5(mm)for PA13 and 4.75～9.5&2.36～4.75(mm)for PA10.The primary structure formation conditions show clear correlation with the stability of the PA13/10 framework in those particle sizes.It was suggested that aggregate contents of 2.36～4.75(mm)particles in PA10 could be increased based on the content of 4.75～9.5(mm)particles under the primary structure formation criterion.The aggregate content within the framework particle size range of PA13 could also take the criterion as a reference.The performance evaluation of surface materials showed that PA13 asphalt mixture with relatively coarse gradation composition and better skeleton stability performed better in high temperature stability,permeability and anti-skid function under high speed and rainy condition,while PA10 asphalt mixture with larger fines content,asphalt content and thicker film was relatively superior in low temperature crack resistance,anti-raveling,water stability,noise reduction function and anti-skid function under low speed condition.Besides,the resistance to raveling and moisture damage after long-term aging condition were considered.It is verified that the performance degradation of the material shows an exponential change trend.Both PA13 and PA10 asphalt mixtures behaved good resistance to raveling when aging time reached 5 days,but the water stability index TSR could not reach the limit value 80%,which means the update for PATO should be done after 5years of its service cycle.Afterwards,the interlayer material design was carried out to determine the final paving scheme.The direct shear test results were used to obtain the distribution law of interlayer shear strength and shear fracture energy with the amount of SBR emulsified asphalt.It is confirmed that the amount interlayer material is 0.6kg/m~2 for PA13 and PA10.The applicability of the cohesion model was verified through combination with results of the direct shear specimen model and test data.The pavement structure models of two paving schemes(3cm-PA13,3cm-PA10)were constructed.It was found that the interlayer performance of two schemes was equivalent in the elastic stage without interface damage under the action of uniform speed moving load(90km/h).For cases with occurring of interface damage,the interlayer resistance of the PA10 scheme performed better according to direct shear test results.It is concluded that PA13 and PA10 paving schemes have their own advantages based on the surface and interlayer performance evaluation result.The best paving scheme should be determined in combination with actual demands and environmental characteristics.Thus,the 3cm-PA13 scheme of test section in this research was determined considering the requirements focused on anti-skid,permeability and high temperature stability,and the overall performance of the test section was good,confirmed the applicability of the optimization suggestions and construction process parameters in the article. |
PDF Full Text Request