A comprehensive review of cementitious grouts: Composition, properties, requirements and advanced performance

Although grouting is a widespread process mainly used for soil treatment and for filling cracks/voids in concrete structures, grout injection is still a challenging step. Due to the different performance required for the numerous fields of application, encompassing several injection methods and different design approaches, it is essential to understand how the components of the grout (cement, aggregates, supplementary cementitious materials, chemical admixtures) affect the workability, stability, injectability, consistency, rheology and, as a result both the composition and the aforesaid properties, also the mechanical strength of the material and the effectiveness and long term performance of the overall grouting application. As a matter of fact, all cementitious materials can suffer deterioration processes that affect the serviceability and durability of structures and jeopardizing their safety, requiring maintenance/recovery works whose cost can, overall the structure life cycle, result even higher than the construction one. This may be especially true in the case of grouting applications, e.g. in prestressed concrete structures, where the state of deterioration is not visible and its non-inspectable progress might lead to catastrophic structural failures. To address all these issues, researchers have developed self-healing cementitious materials which have proved to be an interesting option, as they are able to prolong the lifetime of structures, reducing the environmental impact all along its life cycle. The literature points out that many self-healing mechanisms are effective in concrete and mortars. However, this technology has been barely applied in grouts. In this context, this work presents a comprehensive overview of cementitious grouts with focus on their composition, properties, application technologies and conditions that can affect the overall material and application performance. In addition, this review also provides an overview of self-healing technologies applied to grouts as well as the research gaps in the field of self-healing grouts that should be desirably filled to exploit their benefits in structural and infrastructural applications.