Research On Performance Of Anti Cracking Cement Stabilized Macadam Based On Homogeneity Design

Semi rigid base has the characteristics of high strength,large rigidity,high carrying capacity and good stability.However,there are many defects in engineering practice,which are mainly manifested as shrinkage cracking and fatigue failure.The reason is that as a multi phase composite cement stabilized macadam,it is easy to cause the weak bond surface due to the uneven distribution of the cementitious material and the aggregate.Local damage is caused by the coupling of load and environment,resulting in overall failure.Based on the multistage dispersion and non-homogeneous properties of cement stabilized macadam,the cracking mechanism of the material is analyzed and an ideal structure and composition state to improve the evenness and interface state of the mixture is put forward—“mortar wrapping and filling,and suspended skeleton dense structure”.In order to achieve this state,a hierarchical design method for improving the performance of multi-stage dispersion system is proposed,and the two stage design method including mixture design of cement mortar and cement stabilized macadam is put forward.It is concluded that the first order surplus coefficient K₁ of mixture is 1.2,and the two level surplus coefficient K₂ is 1.45.And the designed mixture is evaluated.Firstly,the distribution uniformity of new cementitious materials and aggregates is quantitatively evaluated and fractal characterization of aggregate gradation is carried out.Fractal deviation is used to evaluate aggregate variability.According to the design method,the coefficient of variation of cementitious material and gradation decreased by approximately 19.2%and 17.6%respectively.Secondly,the comprehensive properties of the mixture are studied from the aspects of mechanical properties,shrinkage and fatigue properties and all have improved to varying degrees Finally,through the SEM-EDS and microhardness,the interfacial transition zone was analyzed from the interface characteristics and microscopic product angles.The results show that the microstructure of the mixture obtained by this design method is relatively compact,with fewer defects.The thickness of the transition zone is reduced by about 27.3%,and the average microhardness is increased by about13.8%.The micro mechanism of the performance improvement of the mixture was revealed.In conclusion,the composition characteristics and cracking failure mechanism of cement stabilized materials are studied and analyzed.The mortar wrapped and filled and suspended skeleton structure improved the uniformity and interface state of the mixture.The properties of the materials have been improved in varying degrees.This paper provides references for reducing composition defects and improving crack resistance of low cementitious material mixture.