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Creep and shrinkage prediction for a heat-treated ultra high performance fibre-reinforced concrete
The work presented is a contribution for the state of knowledge on the time-dependent strains of Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) undergoing a heat treatment at a moderate temperature. The results confirm the significance of the effect of the type of heat treatment used for UHPFRC regarding the time-dependent stains as shrinkage and creep. It is well documented that heat treatments at 90 °C applied to the hardened concrete for almost two days increases concrete mechanical resistance and limit time-dependent strains. The heat treatments at moderate temperature studied here were applied just after mixing the UHPFRC with the aim to accelerate during few hours the hardening process. For UHPFRC undergoing a moderate heat treatment, experimental results show that autogenous shrinkage must be taken into account for the calculation of the time-dependent strains. The French Interim Recommendations on UHPFRC (AFGC/SETRA, 2002) distinguished the UHPFRC with or without heat treatments. The new version of this document will be published in 2012 and would integrate plainly the impact of heat treatments on creep and shrinkage distinguishing heat treatments at moderate temperature applied during few hours after moulding from heat treatments at around 90 °C applied to the hardened concrete. NF EN 1992-1-1 and NF EN 1992-2 standards of Eurocode 2 were not worked out to design UHPFRC structures. Nevertheless, with the help of some adaptations using the methodology described in the annex B of EC2-2 standard, these analytical models allow to calculate creep and shrinkage of UHPFRC when a moderate heat treatment is used. Moreover, Eurocode 2 already take into account the concept of "temperature adjusted concrete age" for temperatures varying between 0 °C and 80 °C. A better prediction of the evolution of the properties of the prestressed UHPFRC products according to the nature of the heating applied should allow the optimization of the production cadences and the energy used for the heat treatments.
Creep and shrinkage prediction for a heat-treated ultra high performance fibre-reinforced concrete
The work presented is a contribution for the state of knowledge on the time-dependent strains of Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) undergoing a heat treatment at a moderate temperature. The results confirm the significance of the effect of the type of heat treatment used for UHPFRC regarding the time-dependent stains as shrinkage and creep. It is well documented that heat treatments at 90 °C applied to the hardened concrete for almost two days increases concrete mechanical resistance and limit time-dependent strains. The heat treatments at moderate temperature studied here were applied just after mixing the UHPFRC with the aim to accelerate during few hours the hardening process. For UHPFRC undergoing a moderate heat treatment, experimental results show that autogenous shrinkage must be taken into account for the calculation of the time-dependent strains. The French Interim Recommendations on UHPFRC (AFGC/SETRA, 2002) distinguished the UHPFRC with or without heat treatments. The new version of this document will be published in 2012 and would integrate plainly the impact of heat treatments on creep and shrinkage distinguishing heat treatments at moderate temperature applied during few hours after moulding from heat treatments at around 90 °C applied to the hardened concrete. NF EN 1992-1-1 and NF EN 1992-2 standards of Eurocode 2 were not worked out to design UHPFRC structures. Nevertheless, with the help of some adaptations using the methodology described in the annex B of EC2-2 standard, these analytical models allow to calculate creep and shrinkage of UHPFRC when a moderate heat treatment is used. Moreover, Eurocode 2 already take into account the concept of "temperature adjusted concrete age" for temperatures varying between 0 °C and 80 °C. A better prediction of the evolution of the properties of the prestressed UHPFRC products according to the nature of the heating applied should allow the optimization of the production cadences and the energy used for the heat treatments.
Creep and shrinkage prediction for a heat-treated ultra high performance fibre-reinforced concrete
Francisco, Philippe (author) / Benboudjema, Farid (author) / Rougeau, Patrick (author) / Torrenti, Jean-Michel (author)
2012
7 Seiten, 4 Bilder, 3 Tabellen, 8 Quellen
Conference paper
English
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