Effects of elevated temperatures on mechanical properties of reactive powder concrete elements

Abstract

Although reactive powder concrete (RPC) is a well-known composite that achieves high rates of compressive strength, its behavior during fire still questionable. This study investigates the mechanical characteristics of RPCs following exposure to high temperatures. RPCs were prepared using high quantities of cement, silica, quartz, and fine aggregates, very small quantities of water (w/c less than 0.25). The testing was carried out on five different RPC mixtures: control mixture (plain RPC), and four test mixtures (RPC with glass, steel, polypropylene (PP), and a hybrid of steel and PP fibers). RPCs were analyzed to explain the original and residual mechanical conduct and spalling during different temperatures between 25 °C and 800 °C. After exposure to elevated temperatures, specimens were testedfor compressive, flexural, and indirect tensile strengths. Appearance and color change, spalling, mass loss ratio, and ultrasonic pulse velocity (UPV) were examined as well.Compressive and tensile strengths for RPC’s mixes and flexural strength for RPC with steel fibers and RPC with steel and PP fibers gradually increases when specimens heated to 200 °C. However, the strengths of all mixes begin to drop as temperatures rise.Although RPC with steel and PP fibers had a high loss of its original compressive, tensile, and flexural strength at 800 °C, this RPC showed the best performance regarding spalling resistance and mechanical characteristics compared to the other types of RPCs. Also, all RPC mixes showedincreasing in mass loss and decreasing in UPV with temperature increase until spalling or became doubtful.