Influence of Marine Environment Exposure on the Engineering Properties of Steel-Concrete Interface

Aims

A detailed and reformed service life prediction model needs to be developed by considering the non-uniform distribution of porous zone as well as the non-uniform distribution of corrosion products layer.

Background

The microstructure of the steel-concrete interface (SCI) plays an important role in corrosion initiation and concrete cover cracking. The porous zone around SCI is one of the vital engineering properties that influence the service life of corroding reinforced concrete structures in service life prediction models.

Objective

The SCI properties are sensitive to the sample preparation technique of reinforced concrete (RC) samples for studying with the aid of scanning electron microscopy (SEM). A simple step-wise sample preparation technique of RC samples for SEM analysis is proposed where there is minimal damage to the properties of SCI. The development, distribution, and propagation of corrosion products at SCI are investigated for RC samples exposed to the marine environment for different exposure periods. The service life of RC structures was assessed through experimentally determined porous zone thickness (PZT) values. Assuming a uniform and constant value of PZT and uniform distribution of corrosion products around SCI might lead to variation or misinterpretation of the service life of structures. The same is explored in the present study.

Methods

In this research investigation, backscattered electron images were obtained for the analysis of porous zone thickness around SCI. The distribution and propagation of corrosion products around SCI was investigated for different mineral admixed reinforced concrete samples exposed to the marine environment. Also, experimentally measured porous zone thickness values were used, and the time from corrosion initiation to corrosion cracking was estimated using a service life prediction model.

Result

Results show that porous zone thickness is not uniform around SCI. Once the corrosion is initiated, the corrosion products start to accumulate in the porous region of SCI. Further, the non-uniform porous zone thickness directly influenced the non-uniform distribution of corrosion products. Assuming a constant or uniform porous zone thickness and uniform distribution of corrosion products around SCI leads to misinterpretation of the service life of corroding reinforced concrete structures.

Conclusion

The porous zone thickness values around the steel-concrete interface and corrosion current density play an important role in predicting the service life of reinforced concrete structures exposed to the marine environment.