Computational Fluid Dynamics Modeling of Fresh Concrete Behavior

Memoria tratta da "The New Boundaries of Structural Concrete: Session B – Controlled-performance Concrete", ACI IC - Ancona 2011

Cementitious composites with adapted rheology are becoming increasingly used in a wide variety of civil engineering applications. Assessing the fundamental rheological properties of cement suspensions is a crucial task, instrumental not only to mixture proportioning of SCC and assessment of its fresh state performance, but also to the design of casting procedures, such as pumping, grouting, underground and underwater injections, etc. For such applications the rheology of the fluid may make a difference in the successful accomplishment of the application. The measurement of the fundamental rheological properties of the cement suspensions is not a simple task. It requires dedicated and expensive equipments in laboratory, which are not compatible with field applications and may not even be available in every laboratory. Correlations between fundamental properties from laboratory and field test measurements are, therefore, desirable and, in some cases, are available, e.g., for the yield stress vs. the spread diameter in slump/mini-slump flow test. As for the viscosity, different attempts have been made, e.g. with the Marsh cone flow time or with the time to reach a prescribed diameter in the slump flow tests. This study aims at providing further evidence to the aforementioned correlations, with reference to a broad range of cement pastes and mortars formulated for high performance fiber reinforced cementitious composites (HPFRCC). A robust assessment by means of computational fluid dynamics (CFD) modeling was performed, employing an approach developed by Cremonesi. The “simulation” of the casting process of a structural element, made with a highly flowable concrete, was performed as an opportunity to address the use of CFD in civil engineering. Such process should allow to “tailor” the material composition and the casting process for the intended application.

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