Abstract
Chloride penetration resistance of concrete is one of the key parameters for the durability design of reinforced concrete structures located in chloride-bearing environments. In all the current available durability models, service life is evaluated considering concrete in uncracked conditions, which is rarely found in practice. This work investigates chloride penetration resistance of concrete in uncracked and micro-cracked configurations, evaluated in terms of chloride migration coefficient through non-steady state migration test (Rapid Chloride Migration test). Prismatic specimens were manufactured considering six different concrete types and two different times of curing. In micro-cracked configuration, cracks were obtained with a specifically developed loading procedure. Micro-cracks were characterized at the end of the exposure test, in terms of crack width at the exposed surface and crack depth. Results showed that cracks were 5–70 μm wide and up to 40 mm deep, always causing an increase in chloride penetration, that should be evaluated considering both crack width and crack depth, with respect to sound conditions. The effects on the chloride penetration seemed to be more pronounced on the more impervious concretes.
Highlights
Chloride-induced corrosion of steel rebar is one of the main detrimental processes affecting the durability of reinforced concrete (RC) structures located in chloride-bearing environments [1]
It can be observed that chloride penetration depths in sound configuration were quite consistent with the measurements carried out in cracked configuration, at distance equal or higher than 10 mm from the central axis, while the chloride penetration depths in correspondence of the crack showed a significant increase
As previously described (Sect. 2.3), the measurements in this case were carried out excluding the influence of the notch, the chloride penetration depth increment was exclusively attributed to the presence of the crack
Summary
Chloride-induced corrosion of steel rebar is one of the main detrimental processes affecting the durability of reinforced concrete (RC) structures located in chloride-bearing environments [1]. Significant efforts have been dedicated to deepen the knowledge of corrosion processes affecting steel reinforcement, and, as a result, to the development of numerous models for the durability design with regard to corrosion prevention These models, present some critical issues, in particular they do not consider the effects of cracks in concrete [2]. On the other hand, loadinduced cracks obtained with Brazilian splitting test [8,9,10,11,12,13] or expansive core method [14] generate tensile cracks in unreinforced concrete specimens of limited dimensions, but crack depth is not controllable and in most cases the crack crosses the entire specimen Another method proposed to generate load induced cracks is the wedge splitting method, which allows to recreate cracks on specimens with specific configuration [15]. The presence of the reinforcement and the dimensions of the specimens (beam-shaped) do not allow to perform traditional chloride penetration resistance tests
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