Residual Mechanical Properties Of Concrete Research Articles

Review of Residual Mechanical Properties of Concrete Mixed with Different Admixtures at High Temperatures

In this study, we analyzed results reported in existing literature to examine the residual mechanical properties of concrete mixed with different admixtures. Ground granulated blast furnace slag (GGBFS), fly ash (FA), and metakaolin (MK) were selected as admixtures for analysis, and data reporting the residual compressive strength of concrete with different admixtures at high temperatures were analyzed. Then, with reference to the ordinary Portland cement (OPC) using 100% cement, prediction formulas for the residual mechanical properties of concrete were derived for each selected admixture, and the resulting values were compared with the values of codes used in international concrete specifications. The residual mechanical properties of concrete showed different results depending on the admixtures used, and the concrete mixed with MK showed a higher compressive strength than OPC at room temperature compared with the values of the existing codes. With increasing temperature of concrete exposure, the trend of compressive strength showed convergence to the values of the existing codes. At room temperature, concrete mixed with GGBFS or FA showed a trend of similar or lower compressive strength compared with that of the existing codes; however, with increasing temperature, the residual compressive strength exceeded that of American Concrete Institute (ACI) and CEN codes. Thus, at room temperature, concrete mixed with MK had excellent compressive strength, but with increasing temperature, concrete mixed with FA or GGBFS was observed to exhibit superior residual mechanical properties.

Residual Mechanical Properties of Concrete with 30% Recycled Concrete Aggregates Exposed to Elevated Temperatures

Residual Mechanical Properties of Concrete with 30% Recycled Concrete Aggregates Exposed to Elevated Temperatures

Review of Ultrasonic Pulse Methods for Evaluation of Mechanical Properties of Concrete with Different Percentages of Non-sintered Hwangto at High Temperature

In this study, the effect of non-sintered hwangto on the high-temperature residual mechanical properties of concrete is analyzed. The specimens are classified as NC and HT, which are mixed with 15% and 30% non-sintered hwangto, respectively, and the W/B is set 0.33. The unit weight, compressive strength, and ultrasonic pulse velocity of the specimens heated at room temperature and at 100 °C, 200 °C, 300 °C, 500 °C, and 700 °C are analyzed, and the correlation between ultrasonic pulse velocity and residual compressive strength is analyzed. The analysis result shows that the higher the mixing ratio of non-sintered hwangto, the lower is the mass loss rate at high temperature and the higher is the residual compressive strength of HT compared with those of NC. Meanwhile, the ultrasonic pulse velocity of HT is similar to or slightly higher than those of NC in areas with high temperatures of 300 °C or beyond. Results of correlation analysis shows a difference of approximately 10.0% between the NC and the HT specimens.

Residual mechanical properties of concrete containing lightweight expanded clay aggregate (LECA) after exposure to elevated temperatures

AbstractThe mechanical properties of light‐weight concrete (LWC) in fire are known to be better than those of normal‐strength concrete (NSC), both at high temperature (hot properties) and after cooling (residual properties). The objective of this paper is to increase the knowledge of LWC's residual properties by testing a number of mixes containing expanded clay as light‐weight coarse aggregate. An experimental program was carried out, in which one normal‐weight concrete mix and two lightweight aggregate mixes containing different amounts of LECA were used to fabricate 72 concrete cylinders and 36 concrete prisms. All mixes contained silica fume as a supplementary cementitious material. The specimens were tested at the ambient temperature and after exposure to temperatures of 250, 500, and 750°C to obtain their compressive and tensile strength, modulus of elasticity, and stress–strain response. Results indicate that exposure to temperatures up to 250°C has no significant effect on the mechanical properties of concrete containing LECA just as in normal weight concrete. However, with increasing the temperature, increasing the lightweight aggregate content of the mix resulted in better strength retention after exposure to elevated temperatures. The experimental data are also used to develop equations to evaluate the residual mechanical properties of concrete.

Effects of High Temperature on the Residual Performance of Portland Cement Concretes

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.