Concrete Spalls: Carbonation vs. Chloride Intrusion
Concrete Spalls: Carbonation vs. Chloride Intrusion
(OP)
Hi,
Is there a visual test an structural inspector can perform to determine if a concrete spall is caused by either carbonation (CARB) or chloride intrusion (CI)? I am not concerned with structural cracks such as flexure or shear cracks that eventually cause a spall. My understanding is that both CARB and CI spalls occur due to the expansion of corroding steel reinforcement, but the mechanisms are different for how the corrosion is initiated.
Essentially, I would like to know if there is a easy visual method to differentiating a CARB and a CI spall without lab testing of chemicals, etc. Maybe the shape of the spall gives it away? Maybe the reinforcement deteriorates in a unique fashion?
Type of concrete structures that pertain to my inspections: prestressed piles, prestressed slab beams, RC columns, RC beams, RC pile caps.
Thanks in advance for any help!
Is there a visual test an structural inspector can perform to determine if a concrete spall is caused by either carbonation (CARB) or chloride intrusion (CI)? I am not concerned with structural cracks such as flexure or shear cracks that eventually cause a spall. My understanding is that both CARB and CI spalls occur due to the expansion of corroding steel reinforcement, but the mechanisms are different for how the corrosion is initiated.
Essentially, I would like to know if there is a easy visual method to differentiating a CARB and a CI spall without lab testing of chemicals, etc. Maybe the shape of the spall gives it away? Maybe the reinforcement deteriorates in a unique fashion?
Type of concrete structures that pertain to my inspections: prestressed piles, prestressed slab beams, RC columns, RC beams, RC pile caps.
Thanks in advance for any help!






RE: Concrete Spalls: Carbonation vs. Chloride Intrusion
Carbonation is rarely deep enough to cause a rebar corrosion issue. It can cause other durability issues, particularly when the concrete is exposed to abrasion or freeze-thaw cycling.
Chlorides can permeate almost any concrete and the effect is direct corrosion of the rebar, resulting in exfoliation and expansion of the rebar, thus causing spalling.
If there is spalling due to carbonation, it will be a near-surface condition, usually less than 1/2" inch deep. Spalling resulting from chlorides will be thicker....all the way to the depth of the rebar.
Other than the noted issues, there is no distinction between the sources of spalling that can be assessed visually.
RE: Concrete Spalls: Carbonation vs. Chloride Intrusion
http://www.concrete-experts.com/pages/carb.htm
I remembered reading about using a phenolphthalein spray some years ago to identify carbonation.
RE: Concrete Spalls: Carbonation vs. Chloride Intrusion
If you spray phenol on the surface of the concrete, that won't tell you anything about the DEPTH of carbonation which is the important factor. For that you need to take cores and have a petrographic analysis done. Ditto for chlorides.
RE: Concrete Spalls: Carbonation vs. Chloride Intrusion
RE: Concrete Spalls: Carbonation vs. Chloride Intrusion