Use 64 Year Old Concrete Bridge Pier for New Bridge

[rockchip]

Is there a good resource for evaluating the structural capacity of a 64-year old reinforced concrete bridge pier? So far, we have identified the following issues: 1)are there discontinuities (cracks, fractures, cold joints, etc.,) where corrosion of reinforcing steel could have compromised the steel; 2) what is the compressive strength of existing concrete (this will probably vary from face to depth of pier); 3) what is the present state of concrete (chemical, and thin section review); and 4) has the steel degraded? Thanks for your resonses. Rockchip

 

[LittleWheels]

Confirm that the reinforcement is as depicted on the As-Constructed drawings. I've had some nasty surprises in the past.

 

[fuchsjr]

You could use a concrete rebound hammer. Core those areas. Then test for compressive strength. Determine a correlation between the rebound and the compressive strength. Then go back and use the rebound hammer on the rest of the structure to test strengths.

If that is not good, you could use impact-echo test equipment to go all the way thru the structure to determine the strength of the concrete.

You could also do freeze-thaw and chloride tests on additional concrete cores. No need to do chloride tests if there is no reinforcement.

Make sure there actually is reinforcement. ;>)

 

[SlideRuleEra]

This will sound trivial, but...

During your analysis be sure to consider the 1940 material properties and construction techniques (examples: rebar steel strength, concrete properties may vary - mixed on job site, by the contractor?, probably no air entrainment, etc.)

I have rejected more than one signed, sealed report because the consultant used "modern" specs to evaluate an older structure.

 

[rockchip]

Thanks to all for the comments and advise. I just wanted to follow up with you all on the project. We ended up coring the concrete pier in an area the structural engineer deemed to have the most severe environmental degredation - that was below and just above the seasonal high water level. Compressive strength testing on 4-inch diameter cores (six tested) ranged from 4,800 to 9,800 psi. There did not appear to be any difference in strength between those from below the water line and those above. However, aggregate (1940's spec?) size may have played a factor in compressive strength as the max size was 3 inches or slightly larger. Aggregates were rounded, quartzitic and quite durable. There did not appear to be any entrained air in the concrete, but it did appear to be compact and with few voids. Where reinforcing was encountered, the rebar was smoooth, 1/2-inch diameter bar with good adhesion with concrete matrix. Surface wear was not severe for 64-year old concrete. Structural engineer has obtained good records of past pier inspections spanning decades and there appears to be no unusual cracking, effluorescence, iron staining/leaching or other indications of serious problems.