Filtern
Dokumenttyp
Sprache
- Englisch (2)
Schlagworte
- Admixtures (1)
- Casting (1)
- Fib model code (1)
- Fibres (1)
- Flowable concrete (1)
- Fresh Concrete (1)
- Mix design (1)
- Modeling (1)
- Rheology (1)
- Robustness (1)
Flowable concretes can differ significantly from traditional vibrated concrete. Concrete types like self-compacting concrete (SCC), ultra high performance concrete (UHPC) and high performance fibre reinforced cementitious composites (HPFRCCs) require novel mix design approaches. This has consequences for the production and the performance in the hardened state. Mix designs for flowable concretes can incorporate a wide variety of innovative admixtures or components: e.g. superplasticisers increase the flowability and allow for significant reduction of the water content, shrinkage compensating admixtures or superabsorbent polymers support sound and damage free curing processes, viscosity modifying admixtures enhance the robustness, and new fibre types allow for sophisticated and tailored structural performance.
The new Model Code has limitations regarding the application of flowable concrete, e.g. thresholds for the minimum aggregate size and the maximum strength. Provisions are added to include fibres for structural design. fib Task Group 4.3 aims at facilitating the use of innovative flowable materials for designing concrete structures and considers three aspects of flowable concrete: material properties, production effects and structural boundary conditions and performance. This paper reports about the progress of fib TG 4.3 related to the mix design of flowable concrete and discusses the present state-of-the-art concerning admixtures and robustness.
First, we define in this paper two benchmark flows readily usable by anyone calibrating a numerical tool for concrete flow prediction. Such benchmark flows shall allow anyone to check the validity of their computational tools no matter the numerical methods and parameters they choose. Second, we compare numerical predictions of the concrete sample final shape for these two benchmark flows obtained by various research teams around the world using various numerical techniques. Our results show that all numerical techniques compared here give very similar results suggesting that numerical simulations of concrete filling ability when neglecting any potential components segregation have reached a technology readiness level bringing them closer to industrial practice.