Novel cement-based composites for the strengthening and repair of concrete structures

In the last 30 years the construction industry branch having to do with the repair, protection and strengthening of concrete has experienced explosive growth. This has been driven by the need to reverse the deterioration of, damage to, and defects in concrete structures as well as by changes in building use and code requirements. Accordingly, there is great need to improve the materials and techniques used in repair and strengthening. This article focuses on novel high-performance fibre-reinforced cement based-composites (HPFRCCs) for strengthening and repair of buildings and infrastructure made of concrete and, in some cases, masonry. Two new types of such material, textile-reinforced concrete (TRC) and strain-hardening cement-based composites (SHCCs), are introduced, highlighting with particular care the benefits and challenges of using HPFRCCs. Specific compositions and production techniques of the composites are presented, followed by a discussion of their mechanical properties in respect of their use on the job. Some reference is made to approaches in considering the load-carrying capacity of the strengthening layers made of HPFRCCs. Furthermore, the transport properties through layers of cracked composites are described as the basis for estimating how well they can protect concrete and its steel reinforcement against ingressing fluids and gases, i.e., against their deterioration. Finally, a number of practical applications of TRC and SHCC are described in order to demonstrate their great potential in the field of rehabilitation of existing concrete structures.

► TRC is particularly appropriate for strengthening of structures subjected to quasi-static loading.
► SHCC is most efficient for strengthening of structures under impact.
► TRC or SHCC repair or strengthening layers can ensure high durability of RC structures.
► Transport of fluids and gases in and through TRC and SHCC depends strongly on multiple fine cracks and their self-healing.
► Practical applications of TRC and SHCC demonstrate their great potential for rehabilitation of concrete structures.