مقاله انگلیسی رایگان در مورد امپدانس بتن آرمه تحت شرایط ماتریکس ترک خورده – الزویر 2018

The electrochemical phenomenon of corrosion is a global source of deterioration of reinforced 35 concrete structures. In environments lacking chloride ions (chlorides), low-carbon steel reinforcing bars (rebar) embedded within concrete form a passive film due to the high pH (ca. 13 to 13.5) of the concrete pore solution and are generally not expected to exhibit any significant corrosion activity during the designed service life of a structure. However, external chloride ions, which originate from sources such as ocean saltwater or deicing salts placed on roadways, can permeate porous concrete cover layers and depassivate the steel rebar after a critical threshold of local chloride concentration has been reached at the rebar surface [1, 2]. After depassivation, corrosion activity of the steel rebar readily increases. As the volume of corrosion products is greater than the sum of the reactant volumes, internal expansion of these products causes concrete cracking [3], subsequently increasing the chloride solution permeability of the concrete 45 [4, 5] and reducing the mechanical performance of the composite [6, 7]. Premature replacement of damaged structures and associated mass consumption of additional construction materials is undesirable due in part to the high energy demands required for concrete production [8]. Because reinforced concrete degradation is dependent on the cracked state of the 49 composite matrix, research of novel crack-resistant construction materials has gained popularity in recent decades [9, 10]. In particular, hybrid fiber-reinforced concrete (HyFRC) is a candidate to reduce corrosion-induced cracking damage due to the mechanical toughening provided by the inclusion of different types of short (e.g., 8-mm to 60-mm long), discontinuous 53 fibers dispersed throughout its cementitious matrix [11, 12]. A crack-resistant concrete such as HyFRC is further advantageous considering that a primary functional purpose of reinforced concrete is to resist mechanical loads, requiring any new implemented construction material to be damage-tolerant against not only corrosion-induced cracking but also structural loading [13, 14]. An increase in the time to corrosion initiation was observed for reinforced HyFRC (i.e., HyFRC composite with embedded steel rebar) compared to reinforced concrete after subjecting samples to flexural stress [15, 16]. While a lower corrosion current density icorr of reinforced HyFRC was also measured compared to reinforced concrete, indicating favorable durability performance after active corrosion had begun, electrochemical characteristics of samples were limited to corrosion potential, polarization resistance, and corrosion current density based on assumed Stern-Geary coefficients. Several corrosion-related studies with different types of fiber reinforced concrete have utilized similar techniques [17-20], making detailed information from certain other electrochemical tests, such as Tafel polarization and electrochemical impedance 66 spectroscopy (EIS), rarely available for fiber-reinforced concrete composites.