Application of Internal Curing in Cementitious Grouts for Prefabricated Bridge Concrete Elements Connections

Cementitious grouts are widely used in construction industry applications, including joint sealing, flooring, structural repairs, and field-cast connections for prefabricated bridge elements (PBE). The authors of this article have a strong interest in the latter application. PBEs facilitate accelerated bridge construction, increase safety, and minimize the inconveniences to the traveling public, while delivering a superior product. While these concrete elements are produced off-site with higher production levels, they rely on the field-cast grout material to complete the connections between them. The ideal grout for PBE connections is self-consolidating, has high early strength, good dimensional stability, good durability, and bonds well to precast concrete. The most common grout type used in PBE connections is based on cement or cementitious materials. This type of grout, however, has at times shown serviceability issues that are mainly associated with dimensional stability (primarily shrinkage), which might also influence the bond to the concrete element. The authors of this article are investigating the possibility of including internal curing (IC) in cementitious grouts with the aim of partially reducing or mitigating most of the shrinkage observed in these materials. The research discusses the particularities encountered in designing IC cementitious grouts, as opposed to conventional concretes, and evaluates the effect that IC has on several grout material properties with special focus on those relevant to PBE connection applications: shrinkage and bond. Results indicate that the inclusion of IC in cementitious grouts reduces both autogenous and drying shrinkage. The effect that this may have on the bond performance is also discussed from a mechanical and microstructural point of view. Finally, an initial cost analysis is provided.