Mechanical Properties of High Performance Self-Compacting Concretes at Room and High Temperature
Résumé
The composition of Self-compacting concretes (SCCs) differs significantly from that of vibrated concretes (VCs). In particular, SCCs generally contain higher paste volumes, larger contents of mineral admixtures and often lower binder to water ratios than VCs. These specific composition parameters allow fulfilling the hard-to-please fresh state requirements of SCCs. However they could also modify significantly their mechanical behavior when concrete is submitted to high temperatures. The main objective of this paper is to study the mechanical behavior of SCCs at room and high temperature. Compressive strength, modulus of elasticity and free thermal strain of 11 self-compacting concretes (SCCs) have been studied at room and high temperature (up to 600 °C). Two series of SCCs are studied: a series in which the mixture proportions of a given concrete are changed in order to vary independently the water/binder ratio and the paste volume and a series with compositions similar to those employed in the precast industry. The variations of compressive strength and modulus of elasticity as a function of the two composition parameters studied are in good agreement with those obtained in the literature for vibrated and self compacting concretes. A relation is given to link the modulus of elasticity of SCC to its compressive strength, which is close to that proposed by ACI 363-2010. The free thermal strain of SCCs is then studied as a function of temperature. Below 300 °C, the free thermal strain of SCCs is larger than that proposed by Eurocode 2 rules for vibrated concrete. Above 300 °C, free thermal strain of SCCs lies between the values proposed by Eurocode 2 for siliceous and calcareous aggregates. The relative compressive strength determined at elevated temperature is generally lower than that proposed by Eurocode 2 for traditional vibrated concrete. The comparison of our results with those determined on several vibrated concretes shows that the obtained relative modulus of elasticity is in the same range. The influence of water to binder ratio and paste volume on these results is discussed.