The Design And Performance Prediction Of Cement Stabilized Materials Based On The Theory Of Framework

Stabilized material with cement is a typical road base material,which should be classified as weak concrete according to the viewpoint of System Theory and the provisions of the "Code for Design of Concrete Structures",For a long time,stabilized material with cement has been used as an independent cement-based material in research and application at home and abroad,with a certain limitation of research thought.Because of extensive availability of stabilized material with cement,and diversified mixture composition,the tests are mainly used in the general design,but the mix design of stabilized material with cement has bigger test workload and long cycle,also is influenced by human factors and environmental factors,the accuracy of the mix design and the representation and comparability of test results need to be improved,macro physical and mechanical performance of the stabilized material with cement and its microstructure influence factors and design improvement measures need to be explored,the prediction on commonly-used mechanical properties of stabilized material with cement in the scientific research and engineering practice need to supplemented and perfected.Based on the above problems,according to the viewpoint of system theory,this study takes the stabilized material with cement as a subsystem of cement-based material,and studies stabilized material with cement according to the structure theory of cement concrete,takes the strength of stabilized material with cement as being composed of coarse aggregate,fine aggregate slurry(pulp)and middle transition layer,considers that the microscopic pore in the structural layer of stabilized material with cement is one of the important factors causing mechanical damage,introduces ultrafine powder filling model(DSP),and expands the original fine pulp structure to ultrafine powder filled slurry structure;in order to realize comparative mechanical properties of stabilized material with cement,by considering the coupling function effect of single factors of stabilized material with cement,DSP filled dense skeleton physical model has been established with main concept of standard stabilized material with cement,deviation of fine pulp ratio,and framework-mortar ratio,and mathematical model of mechanical property with deviation of basic parameters of cement dosage,framework-mortar ratio and fine pulp ratio was put forward.By referring to gap grading design concept of coarse aggregate of stabilized material with cement proposed by the academician Sha Qinglin,this paper made corrections to calculation parameters of gradation composition for CBG-20,CBG-16,CBG-13 and CBG-10,carried out statistical analysis on the mix proportion data of cement concrete and experimental data of stabilized material with cement,as well as the conversion of water-cement ratio of cement concrete and optimum water content of stabilized material with cement,so that the trial mix proportion formula for optimum water content of stabilized material with cement was concluded;By dry ramming coarse aggregate porosity filling method and cement macadam porosity filling method,residual porosity of stabilized material with cement was concluded,and then,the dosage of ultrafine powder(silica fume)was concluded theoretically,and the recommended value of 10%for the amount of ultrafine powder and cement mass in the practical application was presented,and the design method of stabilized material with cement mainly with trial mix proportion under structure theory was eventually formed.In order to compare with the influence of microscopic structure of stabilized materials with cement of standard ultrafine powder filled dense skeleton,with low addition of ultrafine powder and no addition of ultrafine powder on the macro-mechanical properties,first,this paper carried out the comparison of unconfined compression strength test,and observed the morphology of three samples by magnifying 2000 times,5000 times and 20000 times under scanning electron microscopy(SEM),it was found that the microstructures of silica fume mixed materials were the most compact;by comparisons of dry shrinkage and temperature shrinkage tests,the shrinkage property of cement stabilized material with silica fume is better than that of cement stabilized material without silica fume.by calculating the shear stress,displacement and contact force of typical pavement structure with and without adding ultrafine powder through PFC numerical simulation,it was concluded that the pavement base structure with ultrafine powder was obviously better than the pavement structure without ultrafine powder in terms of its force and deformation.In order to ensure the accuracy and high efficiency of mechanical test research,an integrated testing machine for automatic parts,mold release and strength measurement was developed,and the accuracy and working efficiency were given,which also provided reliable guarantee for the testing and inspection in the physical engineering.Then,the fractal study of five types of ultrafine powder filled dense skeleton stabilized material with cement showed that the fractal dimension of the part larger than 4.75mm has an obvious linear relationship with the unconfined compressive strength;in order to determine the correlation degree between deviation of cement dosage,framework-mortar ratio and fine pulp ratio and unconfined compressive strength,grey correlation analysis method was adopted on the basis of the test to obtain the primary and secondary relationship of three main parameters as the deviation of cement dosage>framework-mortar ratio>fine pulp ratio.In order to determine the basic parameters of the mathematical model of structure theory,the relationship between the compressive strength,splitting strength and compressive resilience modulus of five types of stabilized materials with cement and the main influencing factors was regressed through the tests,and the mathematical models of different types of stabilized materials with cement were obtained;finally,DSP filled cement-stabilized construction waste brick,cement-stabilized casting waste sand and iron tailing sand were taken as examples to verify the correctness of the design method and mechanical prediction model of the structure theory through the tests,laying a foundation for the popularization of the extended theory of framework and method to the practical application.