Filtern
Erscheinungsjahr
Dokumenttyp
- Beitrag zu einem Tagungsband (71)
- Zeitschriftenartikel (44)
- Beitrag zu einem Sammelband (37)
- Vortrag (21)
- Buchkapitel (7)
- Posterpräsentation (5)
- Sonstiges (2)
- Forschungsbericht (1)
Sprache
- Deutsch (94)
- Englisch (93)
- Mehrsprachig (1)
Schlagworte
- Beton (18)
- Rheology (13)
- Baustoffe (11)
- Concrete (10)
- UHPC (10)
- AKR (9)
- Zement (8)
- Self-compacting concrete (7)
- Alkali-Kieselsäure-Reaktion (6)
- Repair mortar (6)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (51)
- 7.1 Baustoffe (51)
- 6 Materialchemie (4)
- 6.3 Strukturanalytik (4)
- 4 Material und Umwelt (2)
- 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung (2)
- 7.4 Baustofftechnologie (2)
- 7.0 Abteilungsleitung und andere (1)
- 7.2 Ingenieurbau (1)
- 8 Zerstörungsfreie Prüfung (1)
This chapter provides an overview of methods that are commonly used for the analysis of the original water content of fresh and hardened concrete. The methods consist of direct methods, which detect the water content or the water/cement ratio primarily, as well as indirect methods, which measure other material characteristics related to the water content.
Computational modeling of fresh SCC flow is a comprehensive and time consuming task. The computational time is additionally increased when simulating casting of reinforced sections, where each single reinforcement bar has to be modeled. In order to deal with this issue and to decrease the computational time, an innovative approach of treating a reinforcement network as a porous medium is applied. This contribution presents the model for concrete flow through reinforced sections, based on Computational Fluid Dynamics (CFD), coupling a single-phase flow model for SCC and a continuum macroscopic model for porous medium. In the last part of this paper, numerical simulations are compared with experimental results obtained on model fluids.
Stabilising admixtures are commonly used additives in repair mortars and grouts. Beyond this, such type of admixture is increasingly used in concrete and other cementitious materials. In particular when fresh mortar or concrete properties have to be adjusted reliably, stabilising agents can be beneficially used to improve workability and robustness of the mixture. The mode of operation of these admixtures varies, rather affecting either the liquid phase or the solid particles in the dispersion, both causing strong interactions with the mortar or concrete system, and significant changes in their rheological behaviour. Furthermore, these are strongly affected by the environmental temperature during the casting process. In the paper the effect of temperature on the performance of stabilising agents in cementitious systems is presented and how performance changes affect fresh and hardening mortar or concrete properties. Particular attention is placed on interactions between stabilising agents and superplasticizers. Results are discussed with special focus on self-compacting concrete.
Varying ambient temperatures in plants or on construction sites during casting of SCC can cause serious problems affecting the fresh concrete performances, such as rheological properties and setting time, with consequences for the hardened properties in the structure. By sensible choices of the components, the robustness of SCC mixtures against temperature variations can be improved. However, this aspect has not been the focus of intensive research yet. In this study the effects of varied ambient temperatures on the early performance of differently composed SCC mixtures are investigated, with emphasis on changes in rheology, early deformations, heat evolution and setting. Focus is placed on the study of the influence of the polycarboxylate ether molecule type as well as different viscositymodifying agents on the temperature robustness. Effects on the relevance for practical concrete applications are evaluated, which will provide a reliable framework of possible actions on the appropriate use of admixtures for SCC.