Study On Preparation And Properties Of Full Mechanical Sand Cement Based Rapid Repair Mortar

Cement-based quick repair mortar is composed of coagulation materials,mineral admixtures,aggregates and admixtures,and other raw materials.After a reasonable ratio and water mixing evenly,it has excellent performance such as good construction,fast hard and early strength,dry shrinkage resistance,and non-shrinkage of late strength.It is often used for structural repair and cement concrete pavement repair.In this thesis,based on the composite cementitious material system,the mechanical sand after optimized particle gradation is used to replace all natural yellow sand,supplemented by functional admixtures and mineral admixtures to prepare the full mechanical sand cement based rapid repair mortar,and the influence of each material composition on the performance of the full mechanical sand cement based repair mortar is systematically studied,and the optimal mix ratio is determined.Then,according to the microscopic test,scanning electron microscopy(SEM)phase analysis and X-ray diffraction(XRD)infrared spectrum analysis,that is,analysis of the structure mechanism of the repaired mortar slurry,and finally the optimized mechanical sand repair mortar for trial production.After conducting the research through the above experiments,this thesis draws relevant conclusions:(1)Through the production line of fine machine-made sand and according to the close packing theory,the grain gradation of machine-made sand can be improved.When the ratio of 2.36mm～4.75 mm,0.6mm～2.36 mm and 0～0.6mm sand silo is 0.5:6:3.5,the close packing density and porosity of machine-made sand are better than that of natural yellow sand.The working and mechanical properties of the repaired mortar are the best when the optimized mechanical sand particle grading is adopted and the cement-sand ratio is set as 1.0.(2)When the proportion of ordinary Portland cement and sulfoaluminate cement is1:3,the setting time of repairing mortar system is effectively shortened,and the early strength is greatly improved,which is of great help to catch up with the construction project.Through the analysis of water-binder ratio and admixture test,it can be known that: Appropriate water-binder ratio and appropriate amount of water-reducing agent and defoamer are beneficial to improve the fluidity and mechanical properties of the repaired mortar.The addition of redispersible emulsion powder and cellulose ether can optimize the internal structure of the repaired mortar.The HP-CSA expansion agent can guarantee the micro-expansion effect of the whole process of the repaired mortar.0.30water-binder ratio,0.18% water-reducing agent,0.8% redispersible emulsion powder,0.02% cellulose ether,0.04% defoamer and 1% HP-CSA expansion agent.(3)On the basis of the benchmark mix ratio,the action mechanism of fly ash,wollastonite and limestone powder in the full mechanism of cement based sand repair mortar was studied,and the compound mixing of fly ash,wollastonite and limestone powder was carried out by orthogonal test method.The optimized content of three mineral admixtures was 8% fly ash,4% wollastonite and 6% limestone powder.(4)Through SEM microstructure analysis,there is a dense spatial network structure between the hydration products of the optimized mixing ratio.Through XRD test,the microscopic mechanism analysis and comparison between the benchmark mixing ratio group and the optimized mixing ratio group show that the hydration reaction rate of each age in the optimized mixing ratio group is faster,and the structure of the interfacial transition zone is better improved.Machine-made sand is more closely bonded to cement stone.