Research On Strength And Pore Structure Of Microcapsule Based Self-healing Cementitious Composites

With the function of the intelligent perception and self-healing location for microcrack and damage in cement matrix, microencapsulation technology has become a new trend in the study of self-healing concrete. Mechanical properties are one of the main methods to evaluate the macro performance of microcapsule self-healing cement based materials, and the mechanical properties of concrete are often determined by the microstructure of the materials directly. For a deeper understanding of the microstructure of the cement based materials,modern advanced testing instruments was used to test the microstructure of the cement based materials, and the self-healing effect of microcapsule cement based materials is evaluated from the aspects of microstructure.An organic microcapsule has been synthesized,with E-51 epoxy resin as content and urea-formaldehyde resin as envelope, and the microcapsule has a rough surface and spherical.By controlling and changing the rotational speed of the production process, three different average particle size of the microcapsules were produced, respectively 121.66?m, 184.26?m,286.35?m, and the average particle size distribution、wall thickness and capsule core content of the microcapsules were respectively measured. The content and particle size of microcapsules as variables were mixed into cement mortar,and self-healing cement based materials with different mix ratios were prepared in this paper. To study the influence of the content and particle size of microcapsules on the initial compressive strength and flexural strength of the self–healing cement based materials, the paper find out how strength change with the increase of the content and particle size of microcapsules. With the self-healing rate and recovery rate of compressive strength as indicators, the effect of content and particle size of microcapsule on the self-healing cement-based material was studied. Dynamic Mechanical Analyzer(DMA) was used to measures elastic modulus of cement-based materials. The effect of the amount of microcapsule whose particle size is 121.66?m on the elastic modulus of cement-based material was also studied, and the repair rate and recovery rate of the elastic modulus were used to characterize the self healing effect of the cement based materials. The results show that the self-healing effect of strength of self-healing cement based material ishigher as the increase of dosage and particle size of microcapsules, which means microcapsule have a better self-healing effect on microcracks of cement based material.Nitrogen adsorption method, the mercury intrusion method, XCT method and nuclear magnetic resonance method are used to test self-healing cement-based materials, which respectively get the corresponding pore parameters. To study the influence of the content and particle size of microcapsules on the initial pore parameters of the self-healing cement based materials in different measuring pore method, the paper find out how pore parameters change of different measuring pore method with the increase of the content and particle size of microcapsules. With the self-healing rate and recovery rate of pore parameters as indicators,from microstructure of materials, content and particle size of microcapsule are on the self-healing effect of cement-based material. Discuss mercury porosimetry and NMR porosimetry applied to results of self-healing cement-based materials, which compare the similarities and differences between mercury porosimetry and nuclear magnetic resonance techniques.According to the existing pore size distribution model, the paper establishes the pore size distribution model from mercury intrusion testing pore size distribution of cement-based materials at initial stage, and analyze the physical meaning of pore parameters of the model,and the paper establishes the relational model between the parameters of pore size model and content and particle size of microcapsule. Definition pore parameters self-healing rate and recovery rate of pore size model, the paper establishs the relationship between pore parameters self-healing rate and content and particle size of the microcapsules and the relationship between pore parameters recovery rate and content and particle size of the microcapsules. This paper establishes the strength model and pore parameters of cement-based material at initial stage, which compared and analyzed with the existing model of strength of concrete. Known strength self-healing rate and recovery rate of Chapter II and pore parameters self-healing rate and recovery rate of pore size model of Chapter Ⅳ, the paper established the model between strength self-healing rate and pore parameters self-healing rate of pore size model and the model between strength recovery rate and pore parameters recovery rate of pore size model.