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  • Brouwers, J. (2)
  • Hüsken, Götz (1)
  • Kühne, Hans-Carsten (1)
  • Meng, Birgit (1)
  • Quercia, G. (1)
  • Schmidt, Wolfram (1)
  • Spiesz, P. (1)

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  • 2012 (1)
  • 2010 (1)

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  • Concrete (1)
  • Durability (1)
  • Modified starch (1)
  • Nano-silica (1)
  • Polycarboxylate (1)
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Effects of superplasticizer and viscosity-modifying agent on fresh concrete performance of SCC at varied ambient temperatures (2010)
Schmidt, Wolfram ; Brouwers, J. ; Kühne, Hans-Carsten ; Meng, Birgit
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.
Effects of amorphous nano-silica additions on mechanical and durability performance of SCC mixtures (2012)
Quercia, G. ; Spiesz, P. ; Hüsken, Götz ; Brouwers, J.
In the recent years the application of nanotechnology in building materials has increased exponentially. One of the most referred and used nano-materials is amorphous silica with particles size in the nano-range, even though its application and effect in concrete has not been fully understood yet. It has been reported that nano-silica (nS) addition increases the compressive strength and reduces the overall permeability of hardened concrete due to the pozzolanic properties which are resulting in finer hydrated phases (C-S-H gel) and densified microstructure (nano-filler and anti leaching effects). These effects enhance the durability of concrete structures such as bridges, quays or off-shore oil facilities in marine environments. In this study two different types of nano-silica were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD) but produced in two different processes (fumed powder silica and precipitated silica in colloidal suspension). The influence of nanosilica on SCC was investigated with respect to the properties of concrete in the fresh state (workability) and hardened state (mechanical properties and durability). Additionally, the densification of microstructure of the hardened concrete was verified by SEM and EDS analyses. The obtained results demonstrate that an efficient use of nano-silica in SCC can improve its mechanical properties and durability. Considering the reactivity of the two nano-silica studied, colloidal type shown more reactivity at early age, which influenced all the final SCC properties.
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