New approach needed for forecasting corrosion within bridges, concrete structures
Paradigm shift urgently needed for forecasting corrosion within civil engineering structures

Date:
March 29, 2022
Source:
American Institute of Physics
Summary:
Researchers advocate for a paradigm change in the science
of forecasting corrosion damage within reinforced concrete
structures. They discuss the severe flaws in using the chloride
threshold concept for forecasting corrosion and say change is
needed to address the growing challenges of aging structures
losing functionality and potentially collapsing, greenhouse
gas emissions, and the economy at large. To achieve this, a
multiscale, multidisciplinary approach combining scientific and
practical contributions from materials science, corrosion science,
cement/concrete research, and structural engineering is needed.



FULL STORY ==========================================================================
The most common cause of degradation and failures of reinforced concrete structures is chloride-induced corrosion of its embedded steel. This
is a pervasive, urgent problem that requires immediate attention and
public awareness.


==========================================================================
An underlying concept of a chloride threshold is widely used, and all
existing models to forecast corrosion performance of reinforced concrete structures exposed to chloride environments are based on this one common theoretical concept.

In Applied Physics Reviews, from AIP Publishing, researchers from
Switzerland, the United States, Canada, and Norway advocate for a paradigm change in the science of forecasting corrosion damage within reinforced concrete structures.

Just before the COVID-19 pandemic hit, the international group of
scientists met and discussed the severe flaws in using the chloride
threshold concept for forecasting corrosion. They say change is needed to address the growing challenges of aging structures losing functionality
and potentially collapsing, greenhouse gas emissions, and the economy
at large.

"Corrosion of steel within concrete is a complex phenomenon," said Ueli
Angst, from ETH Zu"rich in Switzerland. "In the generally very high
alkaline environment of concrete, where the pH may be higher than 13,
steel is considered passive, which means it is covered by a thin layer of protective oxides and its corrosion rate is negligibly low." But concrete
is porous, and when exposed to salts, such as seawater or road salts,
chloride ions can eventually penetrate the concrete and reach the steel.

At some point, the protective passive layer will be destroyed, and
corrosion may start. Depending on actual exposure conditions, corrosion
may occur at a faster or slower pace.

In reality, steel corrosion within concrete is a continuous process
rarely separable into uncoupled, sequential phases. The researchers
say the focus should be placed on the quantification of the time- and space-variant corrosion rate from the moment steel is placed within
concrete until it reaches the end of its service life.

To achieve this, a multiscale, multidisciplinary approach combining
scientific and practical contributions from materials science, corrosion science, cement/ concrete research, and structural engineering is
needed. Angst and his colleagues propose scientific research evolve away
from the chloride threshold concept.

"Despite huge amounts of research, no clear chloride threshold could
be found, and the influencing factors are complex," said Burkan Isgor,
from Oregon State University. "Unfortunately, mainstream research is
still in search of this threshold, which presents a major barrier to
developing reliable corrosion forecast models."

========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ueli M. Angst, O. Burkan Isgor, Carolyn M. Hansson, Alberto
Sagu"e's,
Mette Rika Geiker. Beyond the chloride threshold concept for
predicting corrosion of steel in concrete. Applied Physics Reviews,
2022; 9 (1): 011321 DOI: 10.1063/5.0076320 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220329114653.htm

--- up 4 weeks, 1 day, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)