Pin Piles and Galvanizing

[zdude]

Hello,

I have a question that is bugging me. I am working on a residential project where the foundation is supported on 3" dia pin piles. I specified galvanized pipe pipe, but of course it is expensive.

I have been thinking that as these piles are driven into the ground, there is a good chance that the coating will be scraped and rust will start wherever the coating is scratched. My question is

Has anyone specified micropiles? if so, what factors (if any) would justify using galvanized?

for example, the groundwater table is perched, corrosive soils, etc.

Matt

 

[rowingengineer]

zdude,
I never protect the pipe due to the scraping effect; AASHTO includes a provision to deduct 1.6 mm from the shell thickness for the pipe to allow for “sacrificial” steel loss (I normally allow a little more). I would however protect the reinforcement bar when required.
This being the case i will only allow the installation of micro-piles in non- aggressive environments, you could allow for further steel loss, but if you have an aggressive site I would seek specialist advice.

I normally define NON-AGGRESSIVE as:
pH – 5.5 < pH < 10
Resistivity ohm-cm Greater than 5,000
Sulphates ppm(1) Less than 200
Chlorides ppm Less than 100
No chemicals/contaminated land ect.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[Qshake]

We use a lot of micro pile (pin pile) and do not galvanize them or otherwise coat them.

But as rowingengineer states if the soil is a proven problem then consulting a coatings expert or local geotechnical group would be beneficial.

Regards,
Qshake

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[zdude]

Thanks,

After I posted, I thought about an allowance for sacrificial losses, but couldn't quantify a reasonable amount.

Your responses are helpful.