Filtern
Erscheinungsjahr
Dokumenttyp
- Beitrag zu einem Tagungsband (83)
- Vortrag (60)
- Zeitschriftenartikel (37)
- Buchkapitel (5)
- Beitrag zu einem Sammelband (4)
- Posterpräsentation (4)
- Dissertation (1)
- Sonstiges (1)
- Forschungsbericht (1)
Sprache
- Englisch (112)
- Deutsch (75)
- Mehrsprachig (9)
Referierte Publikation
- nein (196) (entfernen)
Schlagworte
- Rheology (42)
- Cement (40)
- Concrete (24)
- Africa (13)
- Rheologie (13)
- Admixtures (11)
- Polysaccharides (11)
- Superplasticizer (11)
- Polycarboxylate ether (9)
- Self-compacting concrete (9)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (33)
- 7.4 Baustofftechnologie (30)
- 6 Materialchemie (6)
- 6.6 Physik und chemische Analytik der Polymere (6)
- 1 Analytische Chemie; Referenzmaterialien (3)
- 1.2 Biophotonik (3)
- 7.0 Abteilungsleitung und andere (3)
- 7.2 Ingenieurbau (2)
- 8 Zerstörungsfreie Prüfung (2)
- 8.0 Abteilungsleitung und andere (2)
Eingeladener Vortrag
- nein (60)
Synopsis: Lately, there has been rising attention to superplasticizers (SP) based on polyphosphate esters. However, the influence of the molecular structure of the polyphosphate polymers on time-dependent properties such as structural build-up has not been examined yet intensively. To investigate this effect, three comb polyphosphate superplasticizers with different charge densities were synthesised by free radical polymerisation. Our findings indicate that SP with the lowest and medium charge densities extend the induction period more strongly than the SP with the highest charge density. The reduction of the structural build-up rate is linearly dependent on the dosage and concentration of the functional group of polyphosphate SP in the cementitious system. This study proposes a mathematical equation expressing the relationship between the structural build-up rate during the induction period and the molecular structure of the polyphosphate SP.
The African-European SPIN Network - Linking Experts to Foster Innovation in Cement and Concrete
(2012)
Most factors acting on concrete rheology work at an extremely small-scale level. Influencing factors in the millimetre or centimetre area are essentially restricted to sand and aggregates. The latter, however, make up 50 to 70% of the total volume of most concretes – a fact often ignored in research on controlling concrete processing properties.
Whereas suitably chosen concrete admixtures and additives can influence rheology in a very targeted manner, sand and aggregates are less suitable for controlling rheology but nonetheless contribute to the rheology of the Overall system. The actions of sand and aggregate can impose themselves upon the actions of admixtures and additives
and, in unfavourable circumstances, even render them redundant. For this reason, any results concerning the processability of binding agent systems can only be transferred to concrete with great care. It is important to better understand the action of sand and aggregates in order to be able to harmonise them in such a way that they complement the action of superplasticisers positively, instead of
working against them. Savings on costs can also be made by this targeted fine-tuning.
Structural build-up describes the stability and early-age strength development of fresh mortar used in 3D printing. lt is influenced by several factors, i.e. the composition of the print able material, the printing regime, and the ambient conditions. The existing modelling approaches for structural build-up usually define the model parameters for a specific material composition with out considering the influence of the ambient conditions. The goal of this contribution is to explicitly include the temperature dependency in the modelling approach. Temperature changes have signifi cant impact on the structural build-up process: an increase of the temperature leads to a faster dissol ution of cement phases and accelerates hydration. The proposed extended model includes temperature dependency using the Arrhenius theory. The new model parameters are successfully calibrated based on Viskomat measurement data using Bayesian inference. Furthermore, a higher impact of the temperature in the re-flocculation as in the structuration stage is observed.