Shuai Zhou

A two-dimensional micromechanical damage-healing model on microcrack-induced damage for microcapsule-enabled self-healing cementitious composites under compressive loading

Concretes with micro-encapsulated healing agents are very appealing due to the advantages of self-healing and the potential for controllable quantifiable healing on a large scale with little initial damage. Based on experimental observation and Taylors model, a two-dimensional micromechanical damage-healing model of microcapsule-enabled self-healing cementitious materials under tensile loading has been proposed. The healing effect on microcrack-induced damage can now be predicted quantitatively by its microscopic healing mechanism. The kinetic equations of damage-healing evolution and the formulations of compliance after healing are developed. Subsequently, simple and efficient numerical simulations are presented and different system parameters of microcapsule-enabled self-healing concretes, such as the radius and volume fraction of microcapsules, fracture toughness of healing agents and initial damage degree, are investigated. In particular, the proposed micromechanical damage-healing model demonstrates the potential capability to explain and simulate the physical behavior of microcapsule-enabled self-healing materials on the mesoscale.

Modeling microcapsule-enabled self-healing cementitious composite materials using discrete element method

Concrete with a micro-encapsulated healing agent is appealing due to its self-healing capacity. The discrete element method (DEM) is emerging as an increasingly used approach for investigating the damage phenomenon of materials at the microscale. It provides a promising way to study the microcapsule-enabled self-healing concrete. Based on the experimental observation and DEM, a three-dimensional damage-healing numerical model of microcapsule-enabled self-healing cementitious materials under compressive loading is proposed. The local healing effect can be simulated in our model, as well as the stress concentration effect and the partial healing effect. The healing variable of the DEM model is developed to describe the healing process. We examine the dependence of the mechanical properties of the microcapsule-enabled self-healing material on (a) the stiffness of the solidified healing agent, (b) the strength of the solidified healing agent, (c) the initial damage of specimens, and (d) the partial healing effect. In particular, the proposed numerical damage-healing model demonstrates the potential capability to explain and simulate the physical behavior of microcapsule-enabled self-healing materials on the microscale.

Evaluation of Self-Healing Properties of Mortar Containing Microencapsulated Epoxy Resin

Under the complex environment of soils, rocks and underground water, the challenges in the repair and maintenance of urban metro structures confront engineers daily. The use of microcapsule-enabled self-healing cementitious composite has high potential as a new repair method for cracked concrete under complex service conditions. The benefit of using microcapsule-enabled self-healing cementitious composite will evidently provide extended durability, service life and security for the metro tunnels. In this study, the self-healing microcapsules enclosing epoxy resins as the adhesive agent are embedded in mortar to achieve the self-healing capability. The properties of healing agents are investigated. The microcapsules are observed by SEM (scanning electron microscope) to obtain the micrographs. The self-healing efficiency is assessed by mechanical restoration of the damaging specimens. The four-point bending test is used. The influence of the content of microcapsules and initial damage is investigated. The results demonstrate that the microcapsule-containing mortar can achieve the mechanical restorations depending on the content of microcapsules and initial damage. Some conclusions about the healing agents and the shell are drawn.

Materials, Theories and Experiments of Microcapsule Self-Healing Method — A Review

The construction of tunnels is booming in China in recent decades. However, the degradation of concrete lining in tunnels seems inevitable, and the challenges in the repair and maintenance in urban metro structures confront engineers daily. The concept of self-healing in concrete was proposed over a decade ago. Concretes with microencapsulated healing agents are very appealing due to the advantages of self-healing, adaptivity to concrete, and the potentiality of controllable, quantifiable healing. The focus of this paper is to summarize the motivation of using self-healing materials and to classify the investigations on the microcapsule-enabled concrete in terms of its components and properties. Relative materials, experiments and theories have been reviewed. Some important factors of microcapsule-enabled, self-healing, underground concrete in urban metro structures are discussed too.