Rebar corrosion can pose a significant threat to structural integrity and safety of buildings, but can be avoided through effective corrosion prevention techniques, comprehensive inspections, and regular maintenance practices.

Corroding rebar in concrete begins with the appearance of rust colored staining. Once this has happened, iron oxides begin to penetrate the concrete and cause significant deterioration to occur.

Staining

Corrosion leaves unsightly rust stains on concrete structures, marring their aesthetics and impacting their aesthetics. Furthermore, it causes cracks in the concrete that lead to expansive forces which weaken it further resulting in structural failure long before expected.

Rebar corrosion can compromise the efficiency and costs of any building by increasing maintenance needs for repairs. Furthermore, it compromises occupant and user safety within that structure.

To prevent corrosion of steel rebar, it is best to utilize coated or galvanized rebar in the construction of structures, which will limit chloride ions’ harmful impact.

Water penetration into concrete, carrying chloride ions with it, is the single greatest cause of corrosion of steel rebar. Chlorides disrupt its passive layer protection, leading to pitting on its surface and pitting at joints. Carbonation may also accelerate corrosion because it alters its alkaline environment into one which promotes rapid corrosion – leaving steel vulnerable against further corrosion.

Cracking

Corrosion at critical levels can damage concrete by cracking it open and revealing exposed rebar, leading to extensive deterioration and structural damage. To reduce corrosion of rebar, an effective anticorrosion treatment must be utilized.

Chlorides, deicing salts, carbonation and more can cause severe damage to concrete. Their corrosion can dismantle its passive layer that protects steel rebar and trigger pitting; water then seeps in through cracks allowing expansion which leads to cracking.

Mak et al and Jiradilok et al [94,96] conducted research on the effect of rebar corrosion on bond behavior using DIC. Their investigation showed that bond degradation corresponded with its extent and width of concrete cracks, however correlating expansive product with corrosion is difficult due to many variables that influence both phenomena (including concrete strength, ratio of cover diameter ratio to diameter diameter ratio and presence/absence of stirrups). They further discovered that corrosion-laden specimens experienced faster bond degradation rates.

Spalling

Cracked and delaminating concrete structures may result from corrosion of rebars, as the corrosive agents released during corrosion permeate into underlying steel materials and cause them to expand, which then weakens their bond with concrete and the rebar, eventually compromising it completely. It should be noted that bond degradation is far more serious than cross-section loss alone.

Rebar corrosion can be effectively prevented through application of a corrosion protection system on the exterior of a building; however, this solution may not always be feasible given its complexity of applying coatings over existing concrete structures.

GPR inspections can quickly identify rebar corrosion and associated structural deterioration, including hyperbolic reflections at longer travel-time distances with lower signal amplitude. Furthermore, structural degradation can be assessed through attenuation and signal polarity; using this data you can spot signs of detachment/debonding/moisture content/high mineral salt content of corrosion within your structure.

Deterioration

Rebar corrosion can significantly compromise a building’s stability. Corroded rebar weakens in tension and compression, potentially leading to its failure and eventually the collapse of an entire structure.

An effective way to prevent rebar corrosion is through protective coatings and concrete treatments. Corrosion protection coatings can keep moisture and chlorides away from contacting metal parts while simultaneously serving as an anode reaction preventer by creating an inert barrier that stops anode reactions from taking place.

Jiradilok et al. [96, 97] found that surface cracking is one of the primary factors contributing to bond strength degradation due to rebar corrosion, due to pore structure limitations which allow only certain quantities of corrosion products before expansive pressure builds up and pressure exceeds their capacity to dissipate.

GPR data confirms this fact by showing zones containing high concentrations of mineral salts to display reduced signal reflections and lower amplitude spectra. Corrosion of concrete rebars poses not only a major structural threat, but can also pose serious threats to those surrounding them and equipment nearby.