Abstract
In this work we analyzed the "residual" performance of Portland cement concretes heat-treated at 600 °C after cooling down to room temperature. Concretes with characteristic compressive strength at 28 days of 45 MPa and of 60 MPa were studied. The heat-treatment was carried out without any imposed load. We measured the residual compressive strength and modulus of elasticity. The geometry of the structure was described by mercury intrusion porosimetry and nitrogen sorption tests. We observed a decrease of residual compressive strength and modulus of elasticity, with the raise of heat-treatment temperature, as a result of heat-induced material degradation. The results also indicated that the microstructural damage increased steadily with increasing temperature. Based on the results of this experimental work we concluded that residual mechanical properties of concrete are dependent of their original non heat-treated values.
Highlights
High-performance concrete is a construction material that has been used in increasing volumes lately
In order to study the effect of transient high temperatures on the residual mechanical properties, we presented linear plots of residual modulus of elasticity, as percentage of their original non heat-treated modulus of elasticity vs. temperature - Fig. 1a - and residual modulus of elasticity, of concretes heat-treated at 600 °C, as percentage of their original non heat-treated modulus of elasticity vs. fck Fig. 1b
From the results of mercury intrusion porosimetry, obtained for non heat-treated concretes, presented in Fig. 2, it appears that both NSC and HSC curves are convex to the pressure axis
Summary
High-performance concrete is a construction material that has been used in increasing volumes lately. The residual compressive strength of the concrete, when cold after heating to various temperatures, is important in connection with the repair of a structure after a fire[12]. With regard to residual properties of concretes, they are extremely relevant, when special structures such as the secondary-containment shells of nuclear reactors or coal-gasification vessels are at issue, where heavy loads have to be carried even after the exposure to high temperatures, whether by accident or not. Scanty information is available on thermo-hygral and thermal-mechanical properties of high-strength concrete[13]. Such information is critical to the design and construction of safe and durable structures[10]. The test program consisted of preparing two concrete compositions and documenting the compressive strength, modulus of elasticity, and pore structure
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