Permeability of Roller-Compacted Concrete after Various Loading Levels

The novelty of this study lies in investigating the simultaneous effects of applied loading, supplementary cementitious materials (SCMs), and interlayer cold joints on the permeability of roller-compacted concrete (RCC). Over 420 RCC specimens were prepared for water permeability, compressive strength, and ultrasonic pulse velocity (UPV) tests in two directions, parallel and perpendicular to the cold joint. A predictive relationship was developed for permeability after loading based on UPV exhibited high correlation and reliability. A sensitivity analysis assessed the impact of the four key parameters—water-to-cementitious material (w/cm) ratio of RCC, water-to-cement (w/c) ratio of mortar, ground granulated blast-furnace slag (GGBFS) content, and the presence of joints—on permeability. ANOVA and the response surface methodology (RSM) were employed to determine the statistical significance of parameters and the influence of layering and arrangement on permeability. The microstructure was examined using scanning electron microscopy (SEM). Test results indicated the enhanced resistance of GGBFS-RCC to stress-induced increases in permeability. A threshold stress level of 40% was identified for RCC’s permeability. Under 20%–40% compressive stress levels, microcracks and pores within the concrete structure gradually closed, reducing permeability. However, when the stress exceeded 40%, crack propagation interconnected with existing internal pores, forming continuous pathways for fluid flow.