Impact strength and weight loss of fiber-reinforced concrete exposed to elevated temperatures

Abstract

The article presents experimental results that were directed to explore the effect of weight loss on the residual repeated impact strength of concrete exposed to high temperatures. The experimental program included the testing of shallow cylindrical specimens under repeated impact loading following the ACI 544-2R test setup recommendations. Five concrete mixtures were prepared for this purpose to evaluate the influence of two major parameters, which are the concrete design compressive strength and the volumetric content of fiber. Three plain mixtures with three levels of design strength including normal-strength and high-strength concrete were prepared in addition to two fibrous mixtures that have the same constituents of the normal-strength mixture. Hooked-end steel fibers were used in the fibrous mixtures at two volumetric contents of 0.5 and 1.0 %. In addition to the repeated impact strength, the compressive strength was also tested using 100 mm cubes. A group of six shallow cylinders and three cubes was tested at room temperature without heating as a reference group from each mixture, while three similar groups were subjected to 200, 400 and 600 °C then tested after natural cooling. The weight loss was recorded for all heated specimens. The results showed that both the specimen weigh and the repeated impact exhibited a trend of continuous decrease with the increase of temperature. However, the repeated impact suffered serious damages after exposure to 200 °C and almost faded after exposure to the higher temperatures, while reasonable decreasing weight losses were recorded at all temperatures.