Research On Performance Of Cement Stabilized Recycled Mixture And Mechanical Response Of Pavement Structure With It

With the rise of the construction industry and the comprehensive coverage of the road network,a large amount of waste concrete has been generated in the demolition of old buildings or road reconstruction,which not only affects the environment,but also takes up a lot of land resources.On the other hand,a large amount of natural stone needs to be consumed in the road construction process.If the waste concrete can be recycled and applied to the road construction,it can not only save natural mineral resources,but also reduce the environmental pollution of the waste concrete.At present,recycled aggregate obtained from crushing and screening of old concrete blocks is mainly used in the pavement base course.However,due to the poor physical and mechanical properties of recycled aggregate,the use of recycled aggregate as the base course material may cause defects such as insufficient strength of the structural layer and prone to shrinkage cracking.By adding a certain proportion of natural aggregate or admixture,the strength and crack resistance of cement stabilized recycled mixture can be improved,so as to effectively improve the recycling rate of old concrete aggregate.The main research contents of this article include:Firstly.Through the comparative analysis of the conventional physical and mechanical indexes of natural aggregates and recycled coarse aggregates,it was found that the crushed value,water absorption rate,needle flake content of recycled coarse aggregates,the mud content index is high,and the apparent density slightly smaller than natural aggregate.Secondly.Under the condition of 5% cement content,with recycled material content,fiber length and fiber volume content as the influencing factors,with 7d and 90 d unconfined compressive strength and 90 d dry shrinkage coefficient as the evaluation indexes,the optimal mix proportion of cement stabilized recycled mixture is determined by orthogonal test analysis.The results show that when the content of recycled coarse aggregate is 60%,the length of fiber is 12 mm and the content of fiber is 0.8 ‰,the comprehensive performance of the mixture is the best.The test results show that the strength,rigidity,frost resistance and shrinkage of cement stabilized recycled mixture can meet the technical requirements under this mixture ratio.Compared with cement stabilized natural aggregate,it is found that there is little difference between them in road performance.The road performance of cement stabilized recycled mixture with polypropylene fiber and polyester fiber was compared and analyzed.It is found that polyester fiber wants polycarbonate polypropylene fiber.Thirdly.Based on the dual modulus theory,the mechanical response of pavement structure corresponding to different thickness of base course and different driving speed is studied when cement stabilized natural aggregate,cement stabilized recycled mixture,polypropylene fiber cement stabilized recycled mixture and polyester fiber cement stabilized recycled mixture are applied to the base course.There is a big difference between the calculation results of double modulus and the traditional calculation results of single modulus,which is mainly manifested in: the bottom tensile stress of base course calculated by double modulus is less than that calculated by single modulus;when single modulus is used,the center of surface layer bottom bears compressive strain,and when double modulus is used,the center of surface layer bottom bears tensile strain;the deflection calculated by double modulus is greater than that calculated by single modulus.