Experimental Study On The Permeable Semi-rigid Base Mixture

Permeable asphalt pavement has good permeable ability and road surface structure depth, its unique maintaining ecological ability and traffic safety also has been more and more countries accepted and to be treated as new roads standards. However, at present, low strenth and not-treated aggregate is used for most of the base of permeable pavement, which is applied to public squares, parking lots and sidewalks, such as light traffic roads. Under middle trafic, for wider range applications of permeable asphalt pavement, developes a permeable semi-rigid material to replace not-treated aggregate which is commonly used. Residents'requirements on the road quality is increasing, the study of permeable semi-rigid material and permeable asphalt pavement has an important academic value and economic benefits.In this paper, in order to reduce semi-rigid material's shrinkage and cracking and improving the road service life, from the mechanism study of semi-rigid material's dry shrinkage and temperature shrinkage, to develope a permeable semi-rigid material based on adding agents and to add layer of steel fiber, including the following three aspects:Firstly, in the mixture proportion design, to aim at the permeability of mixture, the gradation selects skeleton-void structure. Based on regulatory requirements and experience, take porosity and unconfined compressive strength as the control targets, with volume method to design gradation and control Voidage to meet the indicator. In addition to select two representative gradations for indicators'comparison, determining the design gradation is superior to representative gradations. By comparing test results, determined the best ratio of cement and aggregates.Secondly, the composition of cementitious material design, proposed to treat cement, fly ash and expansive agent as a cementitious material. With equivalent fly ash and expansive agent take the place of the cement and the content of aggregates unchanged, that is the internal adding law which is to use fly ash and expansive agent put in the cementitious material. From the part of the construction, the way to add steel fibers is putting steel fibers in the certain layer.Thirdly, pavement performance tests are arranged based on three kinds of ratio between cementitious material and aggregate, simultaneously, composition of cementitious material are different. Pavement performance tests are including: porosity and permeability coefficient test, unconfined compressive strength and resilient modulus test, flexural strength and modulus test, split test, dry shrinkage and temperature shrinkage test. Through the comparison of test data, determine a good mixture in general pavement performance tests.Finally, taking the volume of traffic, designed deflection, soil permeability, level of rainfall and the reproducibility of rainfall, etc into account, assuming the parameters of the pavement'surface layer, the gravel and the soil-based, the best permeable semi-rigid material in performance tests is applied to the permeable asphalt pavement structure design. Through BISAR to calculate pavement structure in two situations of layers completely continuous and not completely continuous,calculations and the results check of the designed permeable asphalt pavement are fully satisfy the norm and the actual usage requirement.