An experimental study of cathodic protection for chloride contaminated reinforced concrete

Cathodic protection (CP) is being increasingly used on reinforced concrete structures to protect steel reinforcing bars from corrosion in aggressive conditions. Due to the complexity of environmental conditions, the design specifications in national and international standards are still open to discussion to achieve both sufficient and efficient protection for reinforced concrete structures in engineering practices. This paper reports an experimental research to investigate the influence of chloride content on concrete resistivity, rebar corrosion rate and the performance of CP operation using different current densities. It aims to understand the correlation between the chloride content and concrete resistivity together with the CP current requirement, and to investigate the precision of the CP design criteria in standards

PROBABILITY FOR CARBONATE STRESS CORROSION CRACKING IN REBARS AND PC RODS IN THE CARBONAETE CONCRETE

The Thirteenth East Asia-Pacific Conference on Structural Engineering and Construction (EASEC-13), September 11-13, 2013, Sapporo, Japan

Multi-term time fractional diffusion equations and novel parameter estimation techniques for chloride ions sub-diffusion in reinforced concrete

In this paper, searching for a better chloride ions sub-diffusion system, a multi-term time-fractional derivative diffusion model is proposed for the description of the time-dependent chloride ions penetration in reinforced concrete structures exposed to chloride environments. We prove the stability and convergence of the model. We use the modified grid approximation method (MGAM) to estimate the fractional orders and chloride ions diffusion coefficients in the reinforced concrete for the multi-term time fractional diffusion system. And then to verify the efficiency and accuracy of the proposed methods in dealing with the fractional inverse problem, two numerical examples with real data are investigated. Meanwhile, we use two methods of fixed chloride ions diffusion coefficient and variable diffusion coefficient with diffusion depth to simulate chloride ions sub-diffusion system. The result shows that with the new fractional orders and parameters, our multi-term fractional order chloride ions sub-diffusion system is capable of providing numerical results that agree better with the real data than other models. On the other hand, it is also noticed from the numerical solution of the chloride ions sub-diffusion system that setting the variable diffusion coefficient with diffusion depth is more reasonable. And it is also found that chloride ions diffusion coefficients in reinforced concrete should be decreased with diffusion depth which is completely consistent with the theory. In addition, the model can be used to predict the chloride profiles with a time-dependent property. This article is part of the theme issue 'Advanced materials modelling via fractional calculus: challenges and perspectives'. </p

Bond characteristics of corroding reinforcement in concrete beams

The results of an experimental study of the bond characteristics of reinforced concrete beams subjected to reinforcement corrosion are presented. Beam specimens recommended by the joint RILEM/CEB/FIP Committee were used, which comprised two halves of a reinforced concrete beam rotating about a hinge mechanism. Corrosion was induced at different levels of rebar diameter loss: 0, 0.3, 0.4, 0.5, 1, 2 and 5 percent by impressing direct current of intensity 0.8 and 2.4 mA/cm(2). The specimens were tested under four point bending to induce bond failure and load - free end slip curves were plotted. The tests showed that at up to 0.4% degree of corrosion, no free-end slip occurred in the reinforcement bars until complete breakdown of bond at failure. At higher degrees of reinforcement corrosion, free-end slip commenced immediately upon application of load and increased linearly with increasing load. The free-end slip at maximum load was a function of the degree of reinforcement corrosion. At small degrees of corrosion, the bond strength increased with increasing degree of corrosion, showing a maximum increase of over 25% at 0.4% corrosion. Higher degrees of corrosion led to a sharp decrease in bond strength