Effect of Curing Regimes and Fiber Contents on Flexural Behaviors of Milling Steel Fiber-Reinforced Ultrahigh-Performance Concrete: Experimental and Data-Driven Studies

The influence of the curing methods on the flexural performances of the milling steel fiber reinforced ultra-high-performance concrete (UHPC) with a high fiber content was systematically evaluated in this study, alongside the flowability and compressive strength. The UHPC specimens were subjected to standard curing and steam curing, employing three steel fiber reinforcing schedules: single milling fiber, single straight fiber, and a combination of both. The flowability of the UHPC was found to be less affected by the milling fiber compared to the straight fiber. Steam curing significantly enhanced the compressive strength but had a slight negative effect on the flexural behavior. However, this adverse effect could be mitigated as the fiber content increased. The flexural strength and toughness of the UHPC with milling fiber were minimally influenced by steam curing, suggesting that standard curing was sufficient for the milling fiber-reinforced UHPC. Conversely, steam curing exhibited an improvement in the flexural behavior of the UHPC containing a hybrid combination of milling and straight fibers. In addition to developing an empirical model for compressive and flexural strengths, we proposed a data-driven model called Gaussian process regression (GPR) to predict the flexural behaviors of the UHPC with varying fiber content, types, and curing methods. The data-driven model demonstrated high accuracy, with an R2 value of 1.0 when compared to the experimental data.