Stress and strain interaction is of vital importance for concrete structures as it has an influence on cracking, deflection and prestressing loss. With the increased range of compressive strengths and flow characteristics, the mixture composition of nowadays concretes often differs considerably from Vibrated Concrete (VC) with regard to paste strength, paste composition and paste volume. As a result, the viscoelastic properties of concrete are altered as well and some of the established stressstrain-relations valid for VC have to be questioned or at least reconfirmed for new concrete types like Self-Compacting Concrete (SCC), Ultra High Performance Concrete (UHPC) and Engineered Cementitious Composites (ECC). This paper discusses time- and load-dependent characteristics of flowable concrete as an outcome of a workgroup within fib Task Group 4.3 that aims at facilitating the use of innovative flowable materials for the design of concrete structures.