Water transport in recycled aggregate concrete under sustained compressive loading: Experimental investigation and mesoscale numerical modelling

Abstract

The durability properties of load-induced damaged concrete incorporating recycled concrete aggregates (RCAs) have previously been reported, but the investigation on water transport in recycled aggregate concrete (RAC) subjected to sustained loading remains to be limited, especially involving both numerical simulation and experimental aspects. This paper presents a comprehensive exploration on capillary water absorption in RAC under various sustained compressive stress levels (λc = 0, 0.1, 0.3, 0.5, 0.7). An improved experimental set-up was self-designed for realizing the coupled action of sustained compressive loading and water absorption by RAC, and then a series of water absorption tests for specimens with different replacement ratios of RCAs (0, 30%, 50%, 100%) were experimentally conducted. The coupled effects of sustained stress level and replacement ratio on the sorptivity of RAC were further discussed. The quantitative correlation between the sorptivity and stress level was obtained to derive the formula of hydraulic diffusivity. Based on the unsaturated flow theory and Mazar's damage variable, the prediction model of water transport in load-induced damaged concrete was established. A mesoscopic model of RAC modelled as a five-phase composite material by considering the old and new interfacial transition zones (ITZs) as interphases was developed and employed to numerically simulate the process of water transport in load-damaged concrete. The mechanical and hydraulic parameters for multiple ITZs of RAC were determined by summarizing the previous studies. The visual numerical results indicate that the distribution of water content and wetting front of penetration depth were remarkably affected by the stress level and the content of RCAs. The comparison of cumulative amount of water absorption indicates that the numerical results agreed well with the obtained experimental measurements, fairly validating the feasibility and accuracy of the developed models. It further illustrates the mesoscopic numerical modelling can be practically adopted to simulate water transport process coupled with sustained loading and also visually exhibit the wetting front of water penetration in RAC.