Framework for the design of capsule-based self-healing cementitious concrete

Abstract

Self-healing concrete has emerged as a viable solution to cracking of concrete and subsequent loss of durability and structural capacity. A multitude of work has been done on the performance of varying combinations of healing capsules and concrete mixes in both experimental and theoretical areas. Due to the lack of standardization in design of self-healing systems, it is difficult to efficiently determine an optimal and cost-effective design. To adequately assess healing effectiveness and healing efficiency, it is necessary to simulate cracks that are representative of realistic crack mechanisms, and corresponding induced local stresses in and around capsules. Analytical and numerical models are still required for the optimization of a self-healing system under different conditions at the design stage, for the properties of self-healing system not only at early-age but also after self-repair of cracks. The present work employs multi-scale theory and probabilistic analyses to develop an engineering framework for determining the probability of crack-capsule intersection and rupture within an early-age self-healing cementitious system. The goal is to provide an efficient tool to aid in the optimization of capsule design for self-healing cementitious systems. Chapter 2 provides a review of background, key issues, and status of research regarding self-healing concrete. Chapter 3 considers the probability for a crack to encounter capsules during cracking. A geometric model is developed to estimate statistical probability for a surface crack to intersect capsules dispersed within a cementitious matrix. In Chapter 4 & 5, a framework considering deterministic and probabilistic approaches is proposed for analyzing capsule behaviour in the vicinity of a crack within a self-healing cementitious composite. A multi-scale multi-step method is developed to determine local stresses and deformation of an individual capsule in a capsule-based composite. This method is extended to consider the impact of shrinkage cracks on local stresses, with crack-induced damage to the matrix.