Mechanical Properties And Permeability Of Microencapsulated Self-healing Cement-based Materials

The problem of easy cracking of concrete seriously affects the durability of buildings.Traditional repairing methods cannot meet the requirements of effective repair of the defects(e.g.,cracks and porosity,etc.)in concrete.The Self-repairing technology has emerged as the times require and gradually become a research hot spot.In this paper,triaxial compression tests,impermeability tests and microscopic measurement(MIP test)are carried out for the mechanical properties and permeability of self-repairing cement-based materials with microcapsules.,and the effects of the content of microcapsules,confine pressure,preloading stress and curing ages on the mechanical properties,impermeability and micro structure of the self-repairing cement-based materials are studied,and establish a predictive model of strength properties and impermeability.The main research results are as follows:(1)The results show that the microcapsules have an important influence on the strength and deformation characteristics of cement-based materials.On the one hand,the strength and cohesion gradually decreased with the increase of the content of microcapsules,accompanying with a negative hybrid effect.The degradation degree of strength and cohesion of the damaged samples increased with the increase of the content of the microcapsules However,the internal friction coefficient slowly increases with the increase of the content of microcapsules.On the other hand,after pre-compression and repair,the peak strain repair rate of the sample decreases with the increase of the amount of microcapsules.However,the elasticity repair rate of the healed samples increased.This indicates that the microcapsules can better repair defects in the damaged cement base materials and improve the overall of the samples after rapid maintenance.(2)In the initial state,when the microcapsule content from 0%to 5%,the chloride ion penetration depth of the test piece is continuously reduced,this indicates that the impermeability of the samples is improved.In the range from 5%to 15%content of the microcapsules,the chloride ion penetration depth gradually increases,this indicates that the impermeability of the samples decreases.The chloride ion penetration depth or impermeability of the samples gradually increases or decreases with the increase of content of the microcapsules under preloading damage condition.With the increase of soaking time from 0 to 120d,the repair rate of the chloride penetration depth gradually increases.Meanwhile,it is also found that the recovery rate of chloride ion penetration depth of the specimen can exceed 100%and the impermeability of the samples exceeds that of the initial samples,when the mixing content of the microcapsules is 15%and the greater than 60 days soaking age.(3)The repair rate and recovery rate of related pore structure parameters are defined to characterize the self-repair effects of the microcapsules on the microstructure of cement-based materials.The relationship model between related pore structure parameters and the dosage of microcapsules,and that of the repair rate,and recovery rate and the dosage of microcapsules are established,so as to predict the pore structure characteristics of self-rep airing cement-based materials and the repair effect on the pore structure parameters under different dosage of microcapsules.(4)Based on the existing relationship model between strength and pore structure parameters,permeability and pore structure parameters,combined with experimental data,the relationship model between pore structure parameters and strength,permeability,repair rate and recovery rate are established,and quantitative analysis and evaluation are carried out.The repair effect of microcapsules on the mechanical properties and impermeability of the material.