Design and self-repair behavior of clay-cured microcapsule composite cementitious materials

Using the round pot granulation method, through the design and optimization of the microcapsule process and formulation parameters, microcapsules with clay solidifying agent, bentonite, MgO expansion agent and microcrystalline cellulose as the core material and ethyl cellulose (EC) as the core material were prepared. For the microcapsules of the wall material, the influence of the components of the microcapsule core material on the self-healing effect of the self-healing microcapsule/cementitious composite material was explored by orthogonal experiments, and the optimal composition of the microcapsule core material was determined: that is, the clay curing agent is 10wt% , MgO expansion agent is 35wt%, microcrystalline cellulose is 6wt%, and bentonite is 49wt%. The results show that the compressive strength of self-healing microcapsule/cementitious composite decreases with the increase of the content of microcapsules. When the content (mass to cement) of microcapsules is 3%, the compressive strength of self-healing microcapsule/cementitious composite is only dropped by 4% with a high strength recovery rate of 103.8%. The deformation behavior of self-healing microcapsule/cementitious composites during loading was traced and tested by the digital speckle correlation method (DSCM). From the stress-strain curve, strain field distribution, gray correlation coefficient eigenvalues (S_tc) and strain eigenvalues (S_ts), the self-healing mechanism of self-healing microcapsule/cementitious composite is based on the fact that when the microcapsules rupture, the cement-based homologous substances(AFt, Mg(OH)₂) are generated to fill the cracks, limit the development of cracks, and achieve the purpose of repairing cracks.