The Influence of Freeze–Thaw Cycles and Corrosion on Reinforced Concrete and the Relationship between the Evolutions of the Microstructure and Mechanical Properties

Abstract

Freeze–thaw cycles (FTCs) and steel bar corrosion (SBC) are the most common service conditions of hydraulic concrete and have significant impacts on its durability. Using pullout and microscopic tests of different FTC and SBC rates, we selected the mass loss rate, ultrasonic velocity, bond strength and bond slip in order to describe the changes in the macro-properties, and also selected the porosity and pore size distribution as micro-parameters in order to explore the influence of FTCs and SBC on the mechanical properties of hydraulic concrete. The results showed that the bond strength decreased as the FTCs increased due to the microstructure damage caused by FTC and SBC, which affects the mechanical properties. A corrosion rate of ≤3% offset the damage caused by 50 FTCs. FTCs and SBC resulted in superimposed damage effects on the concrete. In addition, we established a bond strength damage model based on the joint FTCs and SBC and quantitatively described the degradation law of the macro-mechanical properties. The analysis shows that the influence of FTCs on the bond strength was greater than that of the SBC. These research results can provide a reference and experimental support for the frost-resistant design and durability prediction of hydraulic concrete structures in cold environments.

Influence of Variatropy on the Evaluation of Strength Properties and Structure Formation of Concrete under Freeze-Thaw Cycles

“…Research Topics Main Results [13] The influence of alternate freezing-thawing and corrosion of metal rods on the change in the mechanical properties of concrete Alternate freezing and thawing have a negative effect on the structure of micropores, increases their diameter, and contribute to the acceleration of corrosion processes.…”

Spatially resolved analysis of the progression of freeze‐thaw damage in concrete

“…1. the increase of permeability of the outer structure that can lead to further ingress of aggressive media and thus corrosion of either the steel rebars or the concrete itself [13-15] 2. the change of mechanical properties (like strength or stiffness) in the surrounding of the rebars leading to a reduction of the bond between concrete and steel [16][17][18][19][20] 3. the change of mechanical properties directly leading to a reduction of the structure's load-bearing capacity [21][22][23] For all three factors, it is necessary to evaluate from which depth material loss or a reduction of the strength and stiffness can become critical. Instead of absolute limits normally used as acceptance criteria, the authors propose the use of depth-dependent threshold values for the freezethaw damage comparable to the critical corrosion-inducing chloride content.…”

Investigation of the effect of boron inhibitor on reinforced concrete by using the accelerated corrosion technique

“…Due to the direct and indirect economic losses caused by corrosion, studies for corrosion protection are increasing day by day [1][2][3]. Metals tend to return to their natural state; therefore, it is impossible to completely eliminate corrosion but this process can be slowed down by taking the necessary precautions [4][5][6][7][8][9]. In order for reinforced concrete structures to continue their functions during their design life, some corrosion precautions should be taken.…”