Research On Micro-fine High Performance Grouting Cement

Micro-fine cement(MC) can penetrate into micro-cracks and has almost the same penetration capability as chemical grouting materials. However, the poor rheological property and weak capability of resisting corrosion hinder the application and development of micro-fine cement. Micro-fine high grouting cement(Abbreviation, MHPGC) is a direction of grouting materials development. In this thesis the author systematically research MHPGC's penetration mechanism, rheological behavior, physical and mechanical properties, durability and microstructure. By these work, the thesis reveals the relationship between composition, microstructure and performance in MHPGC. A "sub-cluster" theory was applied to the research on micro-fine cement-based grouting material in this thesis. All these research afford an important theory basis to the design, preparation and application of MHPGC.Through analysis of cement-based material's grouting and filling mechanism and impact factors in micro-cracks, this thesis puts forward the design principle for MHPGC. The research on the relationship between material composition and performance shows that fly ash (FA) can reduce micro-fine cement water-cement ratio and improve its flowability considerably; fly ash composite materials' water-reducing capability has "synergistic effecf'.The influence mechanism of mineral admixtures on the flowability of micro-fine cement paste is their "electrostatic repulsion, ball bearing and filling-and-disperse functions". FA and its composite materials' water-reducing capability derives from these three outstanding functions. By means of optimizing components of MHPGC and fully exerting the properties of one after another hydration of micro-fine cement and fly ash composite materials, the high compressive strength cement paste can be prepared. Although MC is merely forty five percent of the MHPGC, the compressive strength of MHPGC paste was higher than that of neat MC paste, moreover, it is good volume stability and its chloride ion permeability coefficient is also small.By means of DTA, XRD, SEM, EDXA, and MEP, this thesis studied the relationship between microstructure and performance. The result shows that, micro-fine cement hydrates so rapidly that most of cement have hydrated within 28 days, and the CH content is high and increase as time goes by in micro-fine cement paste, which result in its poor ability of resisting erosion; While the CH content in MHPGC paste is low and decrease as time goes by, and Ca/Si ratio of C-S-H in MHPGC paste is also lower than that in pure micro-fine cement paste.Microstruture analysis shows that those center particle sub-clusters(AFt) produced during the early stage of hydration in MHPGC may form three-dimensional netted structure, which enhance the early strength. With the progress of hydration, the hydration product keeps filling in the netted structure to form the composite structure which was similar to compact fiber reinforced composite. Furthermore, as the hydration of fly ash composite materials the cement paste become more and more compact, the early and late strength of MHPGC are both improved. In the interface transition zone of aggregate-paste, the directional degree of CH in micro-fine cement paste is bigger than that of PC paste. While that of CH of MHPGC paste in the interface transition zone is weak. CH crystals' size of micro-fine cement and MHPGC in the interface zone are both bigger than that in their matrixes. However, no matter in the interface zone or matrixes, CH crystals' sizes of MHPGC is always smaller than that of micro-fine cement paste.The sub-cluster statistics theory was applied to the research on MHPGC in this thesis. The material's properties depend on the competition between every level and every type of sub-clusters. As the competition of "coherence and disperse" in cement sub-cluster controls the paste's rheological character, any factor that affect the paste rheological properties are accomplished through influence on this competition. Through the competition between "big pore sub...