Design And Performance Evaluation Of Cement Stabilized Macadam Of Vibration Mixing

The cement stabilized macadam base has the advantages of high strength,good water stability,strong diffusion stress and good economics.It is widely used in China.In the construction process,normal mixing equipment is used to produce the mixture.In order to ensure the strength of the base layer,the higher cement dosage was used,which results in the exposure of defects such as cracks and poor durability during service.As a new technology to improve the quality and performance of building materials,vibration mixing technology is mainly used in the concrete field,and there are few researches on cement stabilized macadam.In this thesis,the physical and mechanical properties of cement stabilized macadam under vibration mixing mode are systematically studied,and the guidance for cement stabilized macadam base construction is proposed.The mix proportion of C-B-3 and C-B-1 cement stabilized macadam mixture was designed by vibration mixing and normal mixing.The results show that the maximum dry density of C-B-3 cement stabilized macadam mixture is 0.011g/cm3 higher than that of normal mixing,the optimum water content is reduced by 6.7%,and the unconfined compressive strength of 7d is higher than 1.06MPa,when meet the strength standard the cement dosage is reduced by 14.3%;the optimum water content of C-B-1 cement stabilized macadam mixture is reduced by 2.8%on average than that of normal mixing,while the maximum dry density is higher than 0.01 g/cm3,and the unconfined compressive strength of 7d is higher than 0.74MPa,when meet the strength standard,the cement dosage is reduced by 12.5%.Based on the strength and shrinkage characteristics,the physico-mechanical properties of cement stabilized macadam under different mixing modes were studied.The grading bearing performance was quantified by the coarse aggregate penetration test,and the relationship between the grading characteristics and the compressive strength of the mixture was studied.The results show that the vibration mixing can improve the compressive strength of the two types of mixing materials.Under the same cement dosage,the unconfined compressive strength of C-B-3 cement stabilized macadam of vibration mixing mode is increased by 16.9%than that of normal mixing,and the C-B-1 cement stabilized macadam of vibration mixing mode is increased by 19.4%;with the increase of cement dosage,the effect of vibration mixing on the compressive strength of the two graded mixture is gradually reduced,and vibration mixing effect of lower cement dosage is the best for the strength improvement of the two grades;at the same cement dosage,the vibration mixing of cracking resistance of the mixture is better than that of the normal mixing;the aggregate grade has a large impact on the compressive strength of the cement stabilized macadam,the coarse aggregate penetration load has a good correlation with the compressive strength of the mixture under the two mixing modes,the coarse aggregate penetration test can preliminarily optimize the gradation.The formation mechanism of cement stabilized macadam strength was summarized,and the mechanism of vibration mixing on mixing uniformity of cement,cement agglomeration and interface transition zone was combed.The results show that the cement hydration process is mainly divided into the dissolution of C3S and C3A and the precipitation process of C-S-H gel and CH and AFt.The two processes promote each other;the failure process of cement stabilized macadam is similar to that of soil particles,and it is affected by cement hydration products,aggregate,grading and compactness;vibration mixing can compensate for the inherent speed gradient phenomenon of normal mixing,improve the mixing low-efficiency zone,eliminate the"hug-axis" phenomenon,and make the fine aggregate evenly wrap on the surface of the coarse aggregate,and enhance the uniformity of the mixture;the cement particles of the flocculation group are broken up,the cement hydration is uniform,the interface transition zone is filled by the C-S-H gel,the pores in the interface transition zone are reduced,the compactness of the mixture structure is improved,and the strength is improved.The titration test was used to test the uniformity of cement dispersion inside the mixing chamber.The grading uniformity of the mixture grading after washing and sieving was studied by means of fractal theory quantitative grading characteristics.The permitted delay time of mixture was studied.The results show that under the vibration mixing mode,the cement dispersion uniformity and gradation uniformity of the two mixtures are better than the ordinary agitation,while the vortex of the C-B-3 and C-B-1 mixture of the vibration mixing is gradually increased with the cement dose;the 7d unconfined compressive strength of C-B-3 and C-B-1 mixture decreased with the increase of delay time,and the permitted delay time of the mixture under vibration stirring mode was better than ordinary stirring.Economic and technical benefit analysis shows that the vibration mixing technology saves money mainly in the stage of cement costs,while the cost of crushed stone is slightly higher than the normal mixing method;overall,the vibration stirring method is more economical than the ordinary mixing method.The difference caused by the equipment cost can be compensated by the paving length;the cost of producing the C-B-3 mixture by the same mixing equipment is lower than that of the C-B-1 mixture.The analysis shows that the strength and crack resistance of the physical engineering of vibration mixing are better than normal mixing.