TY - CONF A1 - Pistol, Klaus A1 - Weise, Frank A1 - Meng, Birgit A1 - Schneider, U. ED - Koenders, E.A.B. ED - Dehn, F. T1 - The mode of action of polypropylene fibres in high performance concrete at high temperatures T2 - 2nd International RILEM workshop on concrete spalling due to fire exposure (Proceedings) N2 - It has been shown in fire tests that polypropylene fibres reduce or avoid explosive spalling of high performance concrete. In the critical temperature ränge up to 300 °C the permeability of HPC increases by using polypropylene fibre. Due to this the water vapour, which is the main reason for explosive spalling, can escape. There exist different theories in the literature conceming the micro structural mechanisms, which cause an increase in the permeability. Within the framework of an internal research project at BAM an innovative methodology was developed for experimental verifying of existing theories and to get new insights into this problem The methodology used is unique and has been undertaken here for the first time. This consists of the combination of acoustic emission and ultrasonic measurement during temperature loading and the non-destructive micro structural analysis of cooled down samples with the aid of micro X-ray computed tomography. For the validation of the nondestructive test methods scanning electron microscopic images of prepared samples were undertaken. The results show that due to the thermal decomposition of the polypropylene fibres micro canals emerge. These are connected due to a simultaneous micro cack formation. T2 - 2nd International RILEM workshop on concrete spalling due to fire exposure CY - Delft, The Netherlands DA - 05.10.2011 KW - Spalling KW - Polypropylene fibres KW - High performance concrete KW - Acoustic emission KW - X-ray computed tomography KW - Scanning electron microscopy PY - 2011 SN - 978-2-35158-118-6 SP - 289 EP - 296 PB - RILEM Publications AN - OPUS4-24835 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Huismann, Sven A1 - Weise, Frank A1 - Meng, Birgit A1 - Schneider, U. T1 - Influence of polypropylene fibres on the thermal strain of high strength concrete at high temperatures JF - Journal of structural fire engineering N2 - This paper presents the results of an experimental study on the influence of polypropylene (PP) fibres on the thermal strain of high strength concrete (HSC) at temperatures up to 750°C. Concerning this topic only few results can be found in the literature and systematic investigations are missing. However, basic knowledge is necessary to understand the internal damage processes as well as for structural design. To explain the differences in the thermal strain of HSC with and without addition of PP fibres the internal damage processes were investigated with acoustic emission (AE) analysis and ultrasound (US). Furthermore the weight loss was measured continuously during heating to monitor the drying of the specimen. This novel approach by combining these different methods with strain measurements at high temperatures allows the integral description of the internal damage processes. The results reveal significant differences in the thermal strain of HSC when PP fibres are added. Between 200°C and 250°C the thermal strain of HSC with PP fibres is superimposed by shrinkage caused by accelerated drying. Above 250°C it is lower than that of plain HSC without PP fibres. It is supposed that it is caused by a more homogeneous distribution of micro cracks whereby the fibre beds acting as defects in the concrete. Hence this paper gives a contribution to the general understanding of the impact of PP fibres in HSC at high temperatures and points out the influence of the fibres on the thermal strain of HSC. KW - High performance concrete KW - High temperatures KW - Polypropylene fibres KW - Thermal strain KW - Acoustic emission KW - Ultrasound PY - 2011 DO - https://doi.org/10.1260/2040-2317.2.3.173 SN - 2040-2317 VL - 2 IS - 3 SP - 173 EP - 179 PB - Multi-Science Publ. Co. CY - Brentwood AN - OPUS4-24817 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Huismann, Sven A1 - Weise, Frank A1 - Meng, Birgit A1 - Schneider, U. ED - Kodur, V. ED - Franssen, J.-M. T1 - Influence of polypropylene fibres on the thermal strain of high strength concrete at high temperatures T2 - 6th International conference "Structures in fire" (Proceedings) T2 - 6th International conference "Structures in fire" CY - East Lansing, Michigan, USA DA - 2010-06-02 KW - High performance concrete KW - High temperatures KW - Polypropylene fibres KW - Thermal strain KW - Acoustic emission KW - Ultrasound PY - 2010 SN - 978-1-60595-027-3 SP - 719 EP - 726 PB - DEStech Publications, Inc. CY - Lancaster, PA, USA AN - OPUS4-21563 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -