Effect of elevated temperatures on mechanical properties of high-strength concrete containing varying proportions of hematite

Aggregates typically constitute 70 to 80 wt\% of concrete, and therefore their type, size, and structure play an essential role in modifying the properties of concrete. When concrete is used for shielding nuclear applications, temperature is also a key factor. This study investigates the effects of elevated temperatures (25 degrees C, 200 degrees C, 400 degrees C, 600 degrees C, and 800 degrees C), heating durations (1, 2, and 3 h), and cooling regimes (air, and water cooling) on mechanical properties of concrete containing different proportions of hematite. A sample of plain concrete was produced for comparison purposes by using river sand, crushed sand, and crushed aggregates. Replacement ratios of 15\%, 30\%, 45\%, and 60\% were used for hematite aggregates. The cement content and water-cement ratio were 450 kg/m(3) and 0.38, respectively. Slump values of fresh concretes as well as unit weight, compressive strength, flexural strength, splitting tensile strength, and elasticity modulus values of hardened concrete were determined. The addition of hematite into concrete seems to improve its mechanical properties, and hematite concretes have better thermal stability at elevated temperatures than plain concrete does. Copyright (C) 2011 John Wiley \& Sons, Ltd