Impact of elevated temperatures on the behavior and microstructure of reactive powder concrete

Reactive Powder Concrete (RPC) is a composite material that will permit the concrete industry to improve material use, generate economic benefits, durable and sensitive to environment. At high temperature due to extremely dense microstructure of RPC shows poor performance owing to the development of high pore pressure that causes the deterioration of the material. By using fiber reinforcement, elevated temperature compression strength and when it is collaborate with the steel the tension strength is increased, as noted by many researchers. This study was aimed to investigate the effect of elevated temperatures on the mechanical and physical characteristics of RPC, containing varying percentages of waste materials as cement replacement. The superplasticizer dosages at the ratios of 1.8% and 2.7% of cement weight were used. The specimens were prepared with 23% silica fume, 23% quartz, 15% granulated slag and two percentages of steel fibers (0.17% and 0.23% by vol.), exposed to two different curing conditions and were subjected to five temperatures, i.e., 20, 200, 400, 500, 600 and 800 degrees C. Later, the specimens were tested for compressive strength test, flexural tensile strength and mass loss test at all temperature ranges. Finally, the degradation of the RPC exposed to high temperatures was estimated by means of the scanning electron microscopy. Experimental results showed that using 0.23% volume fraction of steel fibers, flexural strength of RPC was completely improved. The compressive strength formulated with 15% slag, 23 % quartz powder showed the maximum best mechanical performance at both elevated and normal temperatures. Due to exposed to high temperature, mechanical properties of RPC gradually improves by increasing temperature up to 200 degrees C. The compressive, flexural and tensile strength, decreased at a higher rate of temperatures higher than 200 degrees C. For an exposure temperature of 400 degrees C, results show that the reduction on mechanical properties with deference to the one obtained for room. Furthermore, this mechanical strength exhibited a clear diminution within the temperature range 600-800 degrees C. Using steel fibers in RPC was resisted deterioration, and the amount decrease failure due to high temperatures. (c) 2021 Elsevier Ltd. All rights reserved.