The building industry, and especially the concrete industry, consumes a considerable proportion of the natural resources extracted from the lithosphere and is responsible for a large part of the solid waste generated worldwide. Unfortunately, this fact has not yet generated a movement to counter the trend; rather, a huge increase in the use of concrete in new structures can be observed. It is imperative to counteract this development by optimally exploiting the material properties of concrete in order to improve its efficiency. One strategy being pursued at the University of Natural Resources and Life Sciences, Vienna and TU Wien is to reduce the amount of concrete and reinforcement in structures by using high‐performance materials such as carbon‐fibre‐reinforced polymers (CFRP) in ultra‐high‐performance concrete (UHPC) members. This permits a crucial reduction in the self‐weight and allows for the design of very lightweight precast concrete elements. The authors' goal is to use CFRP rods as bending reinforcement and a combination of flat and preformed CFRP textiles as shear and structural reinforcement. In the first part of this paper, the research approach is introduced and a comprehensive overview of the state of the art of UHPC and CFRP reinforcement is given. The second part contains a description of the conceptual design of some structural members (one floor element and two T‐beams), starting with the development of a suitable UHPC mixture. Furthermore, preliminary uniaxial tensile tests of textile‐reinforced UHPC strips are described and evaluated. In the final part of this paper, the authors present parameter studies for different reinforcement types, values, additional prestressing of the rod reinforcement and the first prototypes. They are used to give an estimation of the feasibility, the load‐bearing and deflection behavior of the proposed building components.

Concrete is the most widely used construction material. Worldwide consumption of cement, the strength‐giving component in concrete, is now estimated to be 4.10 Gt per year, having risen from 2.22 Gt just 10 years ago. This rate of consumption means that cement manufacture alone is estimated to account for 5.2 % of global carbon dioxide emissions.Concrete offers the opportunity to create structures with almost any geometry economically. Yet its unique fluidity is seldom capitalized upon, with concrete instead being cast in rigid, flat moulds to create non‐optimized geometries that result in structures with a high material usage and large carbon footprints. This paper will explore flexible formwork construction technologies that embrace the fluidity of concrete to facilitate the practical construction of concrete structures with complex and efficient geometries.This paper presents the current state of the art in flexible formwork technology, highlighting practical uses, research challenges and new opportunities.

Structural optimization within concrete construction has been increasingly taken up in research within the last two decades. Possible drivers are the need for material-reduced and thus resource-efficient structures as well as recent advancements in automated concrete construction. However, structural concrete is characterized by nonlinear material behavior. Consequently, the merge of structural concrete design and topology optimization is not trivial. This paper reviews and assesses the topic of topology optimization within concrete construction, carrying out an extensive quantitative as well as qualitative review on practical and numerical applications. The following research areas are identified: Multimaterial modeling, stress constraints, concrete damage modeling, strut and tie modeling, combined truss-continuum topology optimization, the consideration of multiple load cases, a focus on construction techniques and alternative approaches. Although the number of research papers dealing with the topic of topology optimization in concrete construction is numerous, there are only few that actually realized topology optimized concrete structures. In addition, only a little number of experiments was performed for an objective evaluation of the found geometries so far. Concluding this review, a list of future challenges, like the incorporation of sustainability measurements within the optimization process, is given and thus serves as a guidance for subsequent research.

Concrete as a construction material is characterized by high compressive strength, low tensile strength, and good casting ability. In order to fully utilize the potential of this material, the form of load-carrying structures has to be designed according to the stress distribution in the structure. Partially hollow structures, such as hollow beams, or doubly curved structures, such as shells, have favorable characteristics. In hollow structures, material savings are achieved in the individual building components by locally reducing dimensions. Concrete shells, if designed properly, are able to span over large areas by transferring the loads mainly by membrane stresses. The main problem with these structures, however, is the high effort required for producing the complicated formwork. One possibility of reducing this effort is to use a pneumatic formwork. This paper describes different pneumatic formwork systems invented in the past 100 years and presents the latest developments in this area. The many types of possible applications are divided into three categories in order to obtain a clearer overview. Finally, a new construction method, called “Pneumatic Forming of Hardened Concrete (PFHC),” is presented. This method was invented at the TU Vienna and uses the pneumatic formwork in a novel way.