Development and experimental validation of a lightweight Stay-in-Place composite formwork for concrete beams

• Cement composites are introduced as a new material for structural Stay-in-Place formwork.
• The new lightweight formwork concept eliminates the need for supporting mechanisms.
• The structural capacity of the formwork eliminates the steel reinforcement.
• 2.8 m span hybrid beams are tested under four point bending.
• The hybrid beams are 28% lighter and 87% stronger than traditional concrete beams.

ContextCurrent formwork research aims towards new cost-competitive formwork systems and materials that focus on labour reduction and efficient material use. This labour cost is reduced when using Stay-in-Place (SiP) formworks. Besides its forming function, SiP formwork can moreover have a protective, an aesthetic or even a structural contribution to the hardened concrete element.ObjectiveUsing cement composites, the authors developed a new Stay-in-Place formwork concept for beams that is lightweight, easy to place and omits steel reinforcement.MethodThis paper describes the conceptual design, the analytical modelling of the loadbearing behaviour and the bending tests that demonstrate its structural feasibility.ResultsUnlike for steel-reinforced concrete beams, serviceability limit state becomes dominant for the developed hybrid beams. As experiments show, hybrid beams with equal stiffness as traditional reinforced concrete beams, have an increased load bearing capacity of 87%, while being 28% lighter.ConclusionThis paper proves the feasibility and potential of structural SiP formworks in cement composites with hollow core elements for future structural applications.