Overview
The quality of reinforced concrete elements depends not only on the average quality of the concrete, but much more on the dispersion of weak areas. In conventional concrete the heterogeneity of the concrete cover is mainly influenced by the compaction process. Among other advantages this fact has first lead Japanese researchers to develop self-compacting concrete. In the meantime this promising material is also applied in Europe and in particular in Sweden and France. In Switzerland so far few tests have been run only. In order to provide a solid basis for the safe application of this new technology the properties of self-compacting concrete are to be optimized.
Self-compacting concrete is usually prepared with comparatively high cement content. Therefore, shrinkage cracking is a real risk. This project aims for minimizing shrinkage strain. This aim may be achieved by adding high modulus fibres or by shrinkage reducing agents. The material is to be optimized with respect to workability and shrinkage cracking.
Funding
Results
Findings were used in several construction projects focused on repair work on civil engineering structures of the Swiss road network (e.g. Schöneich tunnel, underpass Stäfa, groundwater wells of the N40, etc.).
Technical Implications
In this project, the fracture energy has been found as the decisive property for the surface crack formation of non-ductile materials. This property serves as the starting point for optimizing the fibre reinforcement.
Other results
Published results:
Bäuml, M.F., Importance des fibres de renforcement dans le mortiers de réparation, in Transfer 1 – Vers une construction plus durable, D. Rosignoli et M. Martinola (eds.), Sion (CH), 39-50 (2001)
Bäuml, M.F. and Wittmann, F.H., Improved Durability of Self-Compacting Concrete by Addition of Fibers, in Proceedings of the 2nd Int. Symposium on Self-Compacting Concrete, Tokyo (2001)
Bäuml, M.F. and Wittmann, F.H., Application of PVA-Fibre Reinforced Self-Compacting Concrete (ECC) for Repair of Concrete Strucctures , in Internationale Zeitschrift für Bauinstandsetzen, 8, 591-604 (2002)
Bäuml, M.F., Steigerung der Dauerhaftigkeit selbstverdichtender Betone durch den Einsatz von Polymerfaserkurzschnitt, Dissertation ETH Zürich, Diss. ETH Nr. 14837 (2002), in Buliding Materials Report, Nr. 20, Aedificatio Publishers, Freiburg (2003)
Martinola, G., Bäuml, M.F. and Wittmann, F.H., Modified ECC Applied as an Effective Chloride Barrier, Poceedings of the JCCI Int. Workshop on Ductile Fibre Reinforced Cementitious Composites (DFRCC) - Application and Evaluation, Japan Concrete Institut (JCI), 171-180 (2002)
Martinola, G. and Bäuml, M.F., Optimizing ECC in Order to Prevent Shrinkage Cracking, Poceedings of the JCCI Int. Workshop on Ductile Fibre Reinforced Cementitious Composites (DFRCC) - Application and Evaluation, Japan Concrete Institut (JCI), 143-152 (2002)
Wittmann, F.H., Martinola, G., Bäuml, M.F., Frey, R.M. und Meier, S.J., Optimierung des Betons für die Herstellung von Bodenplatten, Proceedings of „Industrial Floors ‘03“, 5th Int. Colloquium in Esslingen (D), P. Seidler (ed.), 37-42 (2003)
Meier, S.J. und Bäuml, M.F., Zur Vermeidung von Rissen in Stahlbetonbauwerken, in Internationale Zeitschrift für Bauinstandsetzen, 9, 173-187 (2003)
F. Beltzung, Influence of alkalies on hygral shrinkage of cementitious composites, 6th International Conference on Materials Science and Restoration, MSR-VI, Karlsruhe, Aedificatio Publishers, 235-244 (2003).
F. Beltzung and F. H. Wittmann, Influence of cement composition on endogenous shrinkage, Proceedings of the Third International Research Seminar on Self-Desiccation and its Importance in Concrete Technology, Eds. B. Persson and G. Fagerlund, Lund (2002).
F. Beltzung, F. H. Wittmann and L. Holzer, Influence of composition of pore solution on drying shrinkage, Rilem Proceedings of Concr