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Timber Embedded in Concrete
2

Timber Embedded in Concrete

Timber Embedded in Concrete

(OP)
Have we reached any conclusions on this?

This was a good thread:
http://www.eng-tips.com/viewthread.cfm?qid=347266

Below is a summary of the discussion if you are going to embed a pole and I would appreciate any added advice:

You should expect a good result for embedding timbers in concrete if:

1. Allow drainage at the bottom
Question - If the wood is to bear on crushed stone at the bottom to allow for drainage, do you assume some sort of skin friction to transfer to the concrete? Should you place dowels through the timber into the concrete to transfer vertical load? Won't the dowels cause faster deterioration of the member?

2. Use preservative treated timber
Question - What type of treatment should be specified? What about Creosote tar?

Thanks!

EIT
www.HowToEngineer.com

RE: Timber Embedded in Concrete

2
The type of preservative is dependent upon the type of wood and the environment it will be in. Creosote works but you may be violating some law. Google this manual from the Agriculture Department, it has a lot of good info.

Preservative-Treated Wood and Alternative Products in the Forest Service by James Groenier, April 2006

It's too large to upload.

RE: Timber Embedded in Concrete

bridgebuster - That document is an excellent summary, thanks!
Here is a direct link to the download:
http://www.fs.fed.us/t-d/pubs/pdfpubs/pdf06772809/...

Table 4, on page 28 gives specific recommendations of the type treatment and retention levels for various suitable preservatives. IMHO, for what is called "Critical Structural" the very best choice is southern pine with CCA-C . That preservative is no longer allowed for residential use in the USA, but it is still available for other applications.

The recommended retention of 0.60 PCF (for CCA-C) may be a little low for poor soils, such as high water table. Other sources recommend 0.80 PCF. The differential cost to go with higher treatment levels is not unreasonable. Twenty-eight years ago, I used southern pine with 2.5 PCF of CCA-C (normally specified for marine construction and at that time readily available where I work) for an important structural foundation in very wet, silty soil. That foundation still looks and performs like it was new.

Again, IMHO, for residential use, the other preservatives and retention rates recommended (other than creosote - for environmental reasons) should give satisfactory performance.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

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