9 - Magnesia in self-healing cement and concrete

Abstract

Self-healing in cementitious systems has recently emerged as an exciting and innovative area of research that has also received significant media attention. This is partly as a result of its biomimetic approaches learning from natural and biological systems and on the other hand its potential to deliver significant savings in terms of cost and carbon. Self-healing in cementitious systems includes a range of autogenous and autonomic processes that could be tailored for specific applications. Magnesia, as an expansive additive, alone or in combination with other expansive additive, within a cementitious matrix, has a role to play in delivering enhanced and effective autogenous healing. The chapter then focuses on the addition of magnesia as an encapsulated entity, to ensure it remains unreactive until needed. Magnesia was added in both powder and granule forms. The powder magnesia was encapsulated in different glass tube systems: single, parallel and concentric, which were positioned within cementitious samples to ensure interception by a crack. Magnesia was also pelletised and coated with PVA. Throughout, the mechanisms of both autogenous and autonomic self-healing using experimental tests and microstructural analyses were explored. Finally field trials were performed in which MgO as an expansive additive and MgO pellets were included in lightweight concrete blocks and commercially used in a new building. This chapter presents selected results from a range of recent research exploring the potential applications for magnesia in the autogenous and autonomic self-healing within cementitious systems.