Development and experimental validation of a lightweight Stay-in-Place composite formwork for concrete beams S. De Sutter ⇑ , O. Remy, T. Tysmans, J. Wastiels Vrije Universiteit Brussel, Faculty of Engineering, Department of Mechanics of Materials and Constructions (MeMC), Pleinlaan 2, 1050 Brussels, Belgium highlights  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. article info Article history: Received 20 April 2013 Received in revised form 25 February 2014 Accepted 24 March 2014 Keywords: Beam Bending Composite Concrete Experiment Hybrid Model Reinforcement Stay-in-Place (SiP) formwork Textile reinforced concrete and cement (TRC) abstract Context: Current 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. Objective: Using cement composites, the authors developed a new Stay-in-Place formwork concept for beams that is lightweight, easy to place and omits steel reinforcement. Method: This paper describes the conceptual design, the analytical modelling of the loadbearing behaviour and the bending tests that demonstrate its structural feasibility. Results: Unlike 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. Conclusion: This paper proves the feasibility and potential of structural SiP formworks in cement compos- ites with hollow core elements for future structural applications. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Formwork costs often transcend more than half of the overall cost of an in-place-cast concrete element [1]. To reduce the cost, reducing the complexity of the formwork system and facilitating the placing of the structural elements are the key to success in the future. Current formwork research aims therefore towards new cost-competitive formwork systems and materials that focus on labour reduction and efficient material use. Over the last years, the increasing worldwide restriction on harvesting has challenged traditional timber and plywood form- works for in-place concrete casting [2]. Re-usable alternatives like prefabricated metal modules exist but are still time consuming due to the process of assembling, disassembling, cleaning and storing. This labour cost is reduced when using Stay-in-Place (SiP) form- works. Besides its forming function, SiP formwork can moreover have a protective, an aesthetic or even a structural contribution to the hardened concrete element. SiP formworks in reinforced concrete are widely used for the erection of floor systems (e.g. half slabs, hollow core slabs). Unfortunately, these formworks retain a high surface weight, require machinery for placing on site and often demand supporting structures during casting. Lightweight alternatives that are http://dx.doi.org/10.1016/j.conbuildmat.2014.03.032 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +32 2 629 29 26. E-mail addresses: svdesutt@vub.ac.be (S. De Sutter), oremy@vub.ac.be (O. Remy), ttysmans@vub.ac.be (T. Tysmans), jan.wastiels@vub.ac.be (J. Wastiels). Construction and Building Materials 63 (2014) 33–39 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat