Experimental investigation on flexural cracking behavior of ultrahigh performance concrete beams

The flexural cracking behavior of ultrahigh performance concrete (UHPC) beams was experimentally studied in this paper. Eight UHPC beams were tested and analyzed regarding their crack pattern, crack spacing and load-crack width curves. The test variables included reinforcement ratio, reinforcement diameter and UHPC cover thickness. The results indicated that crack width of UHPC increased linearly with the increase of applied load until the yielding of steel rebars. When the applied load was beyond the yielding load, one or two flexural cracks developed into localized cracks, followed by a rapid increase in crack width. Besides, increasing the ratio of steel rebars and appropriately decreasing the thickness of UHPC cover were beneficial to decrease mean crack spacing and maximum crack width, whereas reinforcement diameter had little influence on these characteristics. Predictions of crack width by existing FRC/UHPC codes were evaluated and compared with the experimental results. The comparisons indicated that predicted values by NF-P18-710, MC 2010, CNR-DT 204, and RILEM TC-162-TDF models showed a good accuracy with experimental ones. The highest deviation for mean crack spacing and maximum crack width were less than 18 and 8%, respectively. However, CECS 38 model gave the largest deviation about 60 and 25% for prediction of mean crack spacing and maximum crack width, respectively. Among them, NF-P18-710 model exhibited the best accuracy with average ratio and SD of 1.01 and 0.17, respectively.