Study On Engineering Technology Optimization And Application Of Semi-rigid Base Of High-grade Highway In Guangdong Province

Semi-rigid base has excellent structural strength and stiffness,can achieve "strong base,thin surface" effect,has become C hina's most widely used pavement structure form,to ensure the rapid development of high-grade highway in our country.However,the special temperature shrinkage and dry shrinkage characteristics of cement and other inorganic binders can lead to cracks in semi-rigid base.One of the most prominent changes in the new specification "highway pavement base construction technical rules" is to improve the strength of the structural design,which will inevitably make the contradiction between the high strength and cracks in the base more prominent.In this study,based on the cement stabilized macadam material as the object,the relationship between strength and shrinkage performance was established by experimental research,and proposes the evaluation index of the crack resistance,forms material design method to try to solve the contradiction between semi-rigid base strength and crackingFirst of all,according to the raw materials,climatic conditions and traffic load of Guangdong Province,through a lot of compressive strength test,tensile strength test,drying shrinkage test and temperature shrinkage test,the variation rules of compressive strength,flexural strength,dry shrinkage and temperature shrinkage with cement dosage,aggregate gradation,curing age,stone type,water loss rate and temperatur e were analyzed.Based on the analysis of experimental data,established the functional relationship between the 7d unconfined compressive strength and 90 d flexural strength,dry shrinkage coefficient and temperature shrinkage coefficient.According to the 7d unconfined compressive strength,the 90 d tensile strength,dry shrinkage coefficient and temperature shrinkage coefficient can be predicted.Secondly,on the basis of the existing evaluation index of crack resistance,the comprehensive crack resistance index is proposed,and the formula is deduced.The factors influencing the mechanical properties and shrinkage performance were analyzed: gradation and cement dosage.This paper established the 7d unconfined compressive strength and 90 d flexural strength,dry shrinkage coefficient and temperature shrinkage coefficient and aggregate gradation and cement dosage function,combined with the anti cracking performance of the proposed evaluation index,to determine the optimum gradation range of mixture and the best cement dosage range,forming a method of balancing the contradiction between the semi-rigid base strength and cracking,and providing guidance for improving the quality of semi-rigid base in Guangdong Province.Finally,build a test road on the Chaohui Expressway in Guangdong Province,through test road detection and tracking show that to meet the strength requirements of the conditions,the greater the cement dosage,the higher content of fine aggregate,cement stabilized macadam base is more prone to shrinkage cracks,the contradiction between strength and crack can be balanced by cement the appropriate dose and gradation.