The experimental evaluation of the diffusion coefficient and the moisture saturation of basalt fiber reinforced rebar with an anhydride curing agent after climate aging in a cold climate

Abstract Moisture diffusion in basalt-plastic reinforcing bars was investigated during exposing samples in the North conditions for 28 months and in a desiccator above the distilled water surface for 306 days at a temperature of 60 °C. The highest moisture absorption of the initial samples and the exposed samples of BPR does not exceed 0.35%. The initial kinetics of moisture saturation of the initial and exposed samples is similar; the rate of relative mass change is at its maximum at the beginning and reaches a plateau after about 100 days. Due to formation and development of micro- and macrodamages, the kinetics of moisture saturation of exposed samples to an extremely cold climate has a variation. Internal stresses arise in basalt-plastic reinforcement and epoxy anhydride binder in cold climates, owing to the unequal thermal expansion of basalt fiber, and cause the formation of microcracks. The experimental kinetics was approximated by Fick’s law under constant boundary conditions for 6 mm diameter reinforcement bars. A significant change in diffusivity from 16% to 56% and decrease in 20% of maximum moisture saturation for exposed BPR samples in comparison with the stored in warehouse confirms the initial stage of degradation mechanism of reinforcing bars, particularly, uneven destruction of the surface layer and post-curing of the epoxy binder.