Research On The Performance Of Semi-flexible Pavement Materials Filled With Geopolymer

Semi-flexible pavement is a new type of composite pavement composed of asphalt mixture and cement-based grout material.It has the advantages of both asphalt pavement and cement pavement,and is the structure that combines rigidity and flexiblility.However,there are still many problems such as high pollutant emission of cement grout,incompatibility of grout fluidity and strength,and difficulty of compatibility between asphalt interface and slurry interface.Therefore,it is meaningful to adopt low-pollution geopolymer grout material instead of cement as grout material in semi-flexible pavement and study the interface characteristics of semi-flexible material for the development of semi-flexible pavement.The composition design of the parent asphalt mixture--the main part of the semi-flexible pavement material,was studied.In order to ensure the grouting volume,a highly connected and large porosity asphalt mixture is used.The volumetric method was used to design the parent asphalt mixture ratio,and a high connected porosity asphalt mixture with 23%void ratio and 19%connected void ratio of was prepared.The optimal asphalt dosage was determined to be 3.8%by the leakage test and the dispersion test.This paper also studied the composition and performance of the grouting materials,an important component of the semi-flexible pavement material.The response surface method and orthogonal test method was used to determine the ratio of the geopolymer grouting material as 6/4 for raw material m(fly ash/slag),2.3 for alkali activator sodium silicate modulus,5%for sodium oxide content,0.45 for grouting water-binder ratio,0.2 for sand-powder ratio,1%for superplasticizer,1%for shrinkage reducer,and 1%for polymer emulsion.And the geopolymer properties were compared and analysed.The road performance and mechanical properties of semi-flexible pavement materials were studied.And the influence of grouting materials and age change on the properties of semi-flexible pavement materials was analyzed.By comparing the road performance of semi-flexible pavement materials and conventional asphalt pavement materials,it is found that semi-flexible pavement materials have great advantages in high-temperature stability,while low-temperature crack resistance is slightly lacking due to the low temperature and brittleness of grouting materials.The mechanical properties of semi-flexible pavement materials increase with age,and the growth rate is slow in the later stage.Digital image processing method was used to analyze the internal structure of semi-flexible pavement materials.Combined with micro image,the strength mechanism of semi-flexible pavement materials,and the factors affecting the strength of semi-flexible pavement materials were analyzed.By observing the cracks and interface characteristics of semi-flexible pavement materials under the coupling effect of temeperature and load,it is found that stress concentration is prone to appear at the interface,which will eventually lead to the crack and failure of the materials.Finally,methods to improve the properties of semi-flexible pavement materials are proposed from two aspects of material and interface reinforcement.The content of this research and its conclusions can provide a theoretical basis for subsequent development of semi-flexible pavement design,and then promote the further development of high-performance pavement materials.