Progress and challenges in self-healing cementitious materials

Abstract

Concrete is a very common material consisting of a mixture of aggregates (sand, gravel, crashed rock) and paste (cement, water and additives). The paste component, made up mainly of cement and water, degrades with time. Despite this shortcoming, research toward the next-generation cement and concrete materials has intensified in the past 10–15 years. Self-healing cementitious materials, in particular, are a research area that has attracted a great deal of attention. A number of novel formulations have demonstrated an increase in mechanical and chemical stability with respect to conventional Portland cement, through the addition of inorganic, organic, and even biological additives. This review reports on the latest developments in cement research related to the synthesis of cement and concrete materials with autogenous healing and/or self-healing capability. These include geopolymers, engineered cementitious materials, bacterial cement composites, microencapsulated self-healing materials, self-healing assisted by shape-memory alloys, and polymer–cement composites. This work describes the performance of each cementitious material and the mechanism responsible for healing, including a section on atomistic simulations and modeling of cementitious materials. A detailed understanding of various cement technologies with autogenous healing and self-healing properties, including their strengths and weaknesses, is critical to determine the areas where new development is needed to enable novel, energy-efficient, and environmentally responsible cement and concrete solutions. To this end, molecular simulations can play a significant role and have already demonstrated promise in achieving an atomic level view of interactions between cementitious materials and other add-on compounds, such as carbon nanotubes or polymers for enhanced reinforcement or autonomous healing properties. Next-generation construction materials are led by self-healing cement and concrete. With a wide range of autonomous healing strategies based on smart polymers and alloys, biotechnology, and molecular modeling, advanced cementitious materials are becoming part of our daily lives. This work represents a comprehensive review on progress, challenges, and opportunities in the development of these materials for infrastructure and beyond.