Study And Evaluation Of The Self-healing Efficiency On Permeability Of Microcapsule Self-healing Cement-based Material

Due to the effect of the mechanical and environmental load,the cement-based materials are vulnerable to microcracks and local damage.Therefore,growing attention has been paid to self-healing cement based materials.This thesis aimed to develop a type of self-healing cement mortar,which could heal the crack under seepage condition.The preparation technology of microcapsules containing pysical and chemical components and microcapsule self-healing mortar were experimentally investigated;The effects of microcapsule size and content on the mechanical properties and workablity were studied,and the optimized microcapsule size and content were determined;Permeability test device was designed,and permeability tests were used to evaluate the self-healing efficiency of the self-healing cement mortar.With the orthogonal analysis,the optimized compisiton of microcapsule were determined;Meanwhile,the effects of microcapsule content and crack width were also investigated with permeability tests;Based on the kenetics equation of diffusion controlled reaction,and combined with experimental results,the kenetics equation of the self-healing process was proposed.Main conclusions of the thesis were:(1)According to the demands for the self-healing microcapsule,the expansive agent,bentonite,reaction repairing agent and etc.were used as core material and the swelling resin was used as wall material.The self-healing microcapsules were prepared with round pan granulation method.With the orthogonal analysis,the effect of processing factors,such as swelling resin content,raw materials composition and stirring rate,on the productivity of self-healing microcapsules were studied,and the optimized processing factors were determined.(2)Self-healing mortar was prepared with self-healing microcapsules.The effects of microcapsules size and content on mechanical properties and workability of self-healing mortar were studied.The results showed that,with same amount of microcapsules,the effect of microcapsules size on the strength of mortar was not evident.The microcapsule content showed significant influence on the mechanical properties of self-healing mortar.With the increase of microcapsule content,the compressive strength of self-healing mortar decreased.In addition,the workability of self-healing mortar was also evidently influenced by the microcapsule content.With the increase of microcapsule content,the workability of self-healing mortar reduced.(3)The self-healing efficiency of the mortar was evaluated with permeability tests.With orthogonal analysis the optimized composition of microcapsule was determined,which was: bentonite 25%,expansive agent 20%,swelling resin powder 4% and reaction repairing anent 51%.The effects of crack width and microcapsule content on the healing efficiency of self-healing mortar were studied.The results showed that the healing efficiency reduced with crack width and improved with microcapsule content.(4)With X-ray diffraction(XRD)and electron scanning microscope(SEM)analysis,it was found that the healing products were mainly calcium carbonate and ettringite.Based on the test results,the self-healing kinetics model of microcapsule seal-healing mortar was proposed and verified.