Abstract
The microstructural characteristics of high performance concrete (HPC) samples were analysed using scanning electronic microscopy (SEM) and X-ray diffraction (XRD) following thermo-hydraulic and thermo-mechanical testing. The relationship between engineering behaviour (transport and mechanical properties) and microstructure for HPC was then analysed. The failure mechanism of HPC under thermo-mechanical conditions was also discussed. Lower porosity, a higher content of calcium silicate hydrate (C−S−H) and a lower content of the crystalline-phase calcium hydroxide (CH) in both the cement paste and transition zone all exerted a positive influence on the transport and mechanical properties of HPC. By increasing temperature to 200°C, the evaporation of water led to an increase in capillary porosity as well as to a reduction in the cohesive forces between C−S−H layers, which cause degradation of the concrete’s transport and mechanical properties. Microcracking under thermo-mechanical conditions proved to be the main failure mechanism of HPC.
Résumé
Les propriétés microstructurelles des échantillons de béton à haute performance (BHP) ont été analysées par microscopie électronique à balayage (MEB) et diffraction X, suite aux tests thermo-hydrauliques et thermo-mécaniques. Les relations entre le comportement en matière d’ingénierie du matériau (propriétés mécaniques et de transfert) et les microstructures de BHP ont été ensuite évaluées. Le mécanisme de rupture du BHP sous des conditions thermo-mécaniques a aussi été abordé dans ce papier. Un niveau de porosité plus faible, une plus grande concentration en silicate de calcium hydraté (C−H−S) et une concentration plus faible de l’hydroxyde de calcium (CH) à la fois dans la pâte de ciment et dans la zone de transition ont joué une influence positive sur les propriétés mécaniques et de transfert des BHP. En élevant la T° à 200°C, l’évaporation de l’eau a conduit à une augmentation de la porosité capillaire de même qu’à une réduction des forces de cohésion entre les couches de H−S−C, engendrant une dégradation des propriétés mécaniques et de transfert du béton. Les microfissures sous l’effet des conditions thermo-mécaniques se sont avérées être la cause principale de dégradation mécanique du BHP.
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Editorial Note. Prof. Z. Li is a RILEM Senior Member. Prof. G. Ballivy and Prof. K. Khayat work at the CRIB—University of Sherbrooke, a RILEM Titular Member.
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Li, X.J., Li, Z.J., Onofrei, M. et al. Microstructural characteristics of HPC under different thermo-mechanical and thermo-hydraulic conditions. Mater Struct 32, 727–733 (1999). https://doi.org/10.1007/BF02905069
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DOI: https://doi.org/10.1007/BF02905069