Durability assessment of a tunnel structure with two‐sided chloride ingress—A case study located in a tropical environment

Abstract

Reinforced concrete structures are the backbone of the transportation infrastructure. Their structural safety and functional performance are critical to sustaining a globalized economy. Corrosion of steel reinforcement is typically triggered by chloride contamination and carbonation, becoming a primary factor in reinforced concrete deterioration. This paper presents a durability assessment of a tunnel structure located in a tropical marine environment. The condition assessment included visual examination, crack survey, cover depth measurements, half-cell potential mapping, and concrete coring. The chloride profiles showed that the tunnel walls are subjected to chloride attack from both surfaces, an unusual finding in the literature.A stochastic approach is implemented to estimate the probability of corrosion initiation for chlorides and carbonation, including an innovative model for two-sided chloride diffusion. The results indicate that two-sided chloride exposure significantly reduces the corrosion initiation time.

Diffusion model of sulfate ions in concrete based on pore change of cement mortar and its application in mesoscopic numerical simulation

“…Equation ( 1) can be used to simulate the diffusion process of chloride ions, 46 and analytical solutions are available. 47 However, sulfate ions are different from chloride ions, which react with the hydration products of cement, thereby changing the porosity of the cement mortar and affecting the diffusion coefficient. [48][49][50] Therefore, Gospodinov et al 51 proposed an improved model that considers the sulfate reaction based on Fick's second law, and Zuo et al 52,53 improved it to obtain the model shown in Equation (2) to simulate the unsteady diffusion of sulfate ions in cement mortar.…”

“…Equation () can be used to simulate the diffusion process of chloride ions, 46 and analytical solutions are available 47 . However, sulfate ions are different from chloride ions, which react with the hydration products of cement, thereby changing the porosity of the cement mortar and affecting the diffusion coefficient 48–50 .…”

Economic assessment of corrosion prevention measures in new structures

“…The current European standard for durability follows a prescriptive approach [3] in which limit values are set for the concrete cover, maximum water/binder ratio, minimum compressive strength and minimum cement content based on the qualitative evaluation of the exposure conditions (exposure classes). Nevertheless, some studies have shown that some RC structures exposed to severe chloride environments do not achieve their designed service life, despite complying with the current standards for durability design in RC [4][5][6].…”

Experimental investigation of corrosion effect on bending deflection of shield tunnel segment containing transverse cracks

“…For the subway tunnels buried underground, once load-induced cracks develop in a segment, the chloride ions in the groundwater, especially in the offshore strata, will rapidly penetrate to the rebar surface through cracks, resulting in rebar corrosion. [5][6][7] Additionally, if the insulation between the track bed and the rail is impaired due to external environmental factors, [8][9][10] the stray current generated by the subway train traction power will flow through the segment rebar, as shown in Figure 1. Relevant tests have shown that the stray current in the rebar will not only Discussion on this paper must be submitted within two months of the print publication.…”

“…Previous case studies 2–4 have shown that the load‐induced cracks on the surface of the segments are mainly transverse cracks. For the subway tunnels buried underground, once load‐induced cracks develop in a segment, the chloride ions in the groundwater, especially in the offshore strata, will rapidly penetrate to the rebar surface through cracks, resulting in rebar corrosion 5–7 . Additionally, if the insulation between the track bed and the rail is impaired due to external environmental factors, 8–10 the stray current generated by the subway train traction power will flow through the segment rebar, as shown in Figure 1.…”