Bernd Hillemeier

Untersuchung betontechnologischer Fragestellungen mit Hilfe eingebetteter flexibler faseroptischer Fabry—Pérot-InterferometerInvestigations of Durability Parameters of Concrete by Means of Embedded Flexible Fiber-Optic Fabry—Pérot Interferometers

Zusammenfassung Die Dauerhaftigkeit von Betonbauteilen zu einer messbaren Größe zu machen, ist ein vorrangiges Ziel der Baustoffforschung. Schrumpfen, Schwinden und Temperaturverformungen gefährden bei Hochleistungsbetonen deren Dauerhaftigkeit. Die begleitende messtechnische Deformationsmessung wird daher zu einer unverzichtbaren Methode, Betonrezepturen zielsicher und ökonomisch hinsichtlich der Dauerhaftigkeit zu entwickeln. Ein flexibler Fabry–Pérot-Interferometer-Sensor ermöglicht die messtechnische Erfassung der frühen Deformationsprozesse bereits ab dem Moment des Betoneinbaus. Der Artikel zeigt das Sensorprinzip, Untersuchungen zur In-situ-Referenzierung und zur Rückwirkung des Sensors sowie dessen Einsatzmöglichkeiten in der Baustoff- und Materialforschung.

Fast Non-Destructive Localisation of Prestressing Steel Fractures in Post-Tensioned Concrete Bridges

Professor Reinhardt and his employees are besides us at the Technische Universitat Berlin the experts in using the permanent magnetism to determine the health of prestressed concrete structures to find out whether they are free of prestressed wire breakages or whether they must be repaired. Professor Reinhardt enjoys an extremely high technical reputation in civil engineering, this does not have to be emphasized. I would like to stress that Professor Reinhardt is a quite special colleague regarding his kindness, his helpfulness, humanity and modesty. One has many comrades in arms but only few colleagues. I would like to take this opportunity to thank him for much good advice and for the fact, that I have a trusting, reliable and high appreciated colleague in him. I would like to now turn to a topic that connects us both.

Lessons Learnt, Open Research Questions and Recommendations

This chapter represents the summary of the common analysis within the Interdisciplinary Research Group Society – Water – Technology. Lessons learnt, research gaps and recommendations are presented as the outcome of the analysis of the two case studies Fergana Valley and Lower Jordan Basin and as a conclusion from the cross-analysis based on the evaluation framework and the considerations outlined in Chap. 3 (Bismuth et al., Research in two cases studies: (1) Irrigation and land use in the Fergana Valley and (2) Water management in the Lower Jordan Valley. In: Huettl RF, Bens O, Bismuth C, Hoechstetter S (eds) Society water technology: a critical appraisal of major water engineering projects. Springer, Dordrecht, 2015, in this volume).

Membranes Made of Hardened Cement Paste for Processing Wood Gas—Influence of Paste Composition on Separation Factors

The efficiency of wood gasification can be improved by applying membrane based gas separation operations in several of its sub-processes. In the present study the use of membranes made of hardened cement pastes for this purpose was investigated to provide a low cost alternative to conventional membrane materials. The pastes were tested for their diffusional properties in a Wicke-Kallenbach cell and analyzed with regard to their pore structure. The use of low water to binder ratios and slag and/or pozzolans led to a finer pore structure and higher separation factors; in particular, an approximately linear dependence of the separation factors on the threshold radii was observed. The results implicated that Knudsen diffusion is the prevailing diffusion mechanism in the membranes. Deviations from the theoretically expected separation factors were found, which may be ascribed to concentration polarization and channeling effects.

Enhancing Durability of Structures by Monitoring Strain and Cracking Behavior

Powerful testing methods are available for the diagnostics of engineered structures. Promising methods in the laboratories should be developed for application in practice. Responsible owners are capable of maintaining durability in their structures at low cost by a better planning during use.

How to achieve the desired strain transfer for fibre optic microdeformation measurements in cementitious building materials at early ages

Compliant FPI-sensors were used to measure mortar deformation at very early ages with high strain resolution. An appropriate design of alternative coatings to achieve reliable bonding between fibre sensor and cement matrix is described.