Full surface inspection methods regarding reinforcement corrosion of concrete structures

Abstract

For reinforced concrete structures a localisation of all significant critical areas can only be done by a full surface inspection. The economic advantages are obvious: uncritical areas have not to be repaired expensively [1]. The first step of the assessment should always be a visual inspection [2]. The range of deterioration causes can be limited and the degree of deterioration may be estimated roughly. The inspection program can be adjusted to the requirements. By means of a full surface potential mapping areas with a high risk for chloride induced reinforcement corrosion can be localised, although no deteriorations are visually detectable at the concrete surface. In combination with concrete cover depth and resistivity measurements areas with corrosion promoting exposure conditions can be localised even if the reinforcement is not yet depassivated. The following publication gives an overview about the essential full surface investigation methods to localise critical areas regarding corrosion of steel in concrete. The selection of methods is based on the inspection procedure given in [2]. IVDefects that can, in the foreseeable future, decrease the reliability of the structure. Repair is needed on the short term/immediately Delamination and spalling of concrete cover, corrosion stains and damage at the concrete surface, decrease of rebar cross-section V Defects that present a serious danger for safety of the structure. Intervention is needed immediately Delamination and spalling of larger concrete areas, progressive corrosion processes visible, significant decrease of rebar cross-section

Corrosion resistances of passive films on low‐Cr steel and carbon steel in simulated concrete pore solution

“…Hence, in saturated Ca(OH) 2 solution, the addition of small amount of chromium element to CS may change the components of the passive film. Figure 10 also 3 and FeOOH. On the other hand, O 2À is also the primary constituent of the passive film, which corresponds to the formation of FeO.…”

“…9, the chromium peaks could be seen in 3Cr steel, and the chromium profile showed mainly two peaks: Cr(OH) 3 (577.1 eV) and CrO 3 (578.2 eV). The content of Cr(OH) 3 and CrO 3 is calculated by using Xpspeak 4.1 software, and the calculated Cr(III) : Cr(VI) ratio is 0.58 which are listed in Table 5. Hence, in saturated Ca(OH) 2 solution, the addition of small amount of chromium element to CS may change the components of the passive film.…”

“…Because HRB400 steel has limited anti-corrodibility, the early failure of reinforced concrete structure caused by chloride attack and carbonation is widespread and causes great loses in economy. [3,4] Numerous strategies are available for increasing the service life of reinforced structures exposed to chloride salts. [5][6][7][8][9][10] However, all these methods have their own defects.…”

Local detailed inspection methods regarding reinforcement corrosion of concrete structures

“…Based on the recommended inspection strategy in ref. 2 local inspections should always be carried out after the evaluation of a full surface survey 1. The aim of local inspections should be the assessment of the type and extent of deterioration.…”

“… Abstract Full surface surveys which are likely to include e.g. a deterioration and potential mapping as well as a cover depth survey, should be the base to identify critical areas which are suspect to be suffering from reinforcement corrosion 1. Localised assessment in these areas should give further information about the type and extent of deterioration.…”