Trouble spotted on GRR's Oct2007 cover shot

[Marty Cozad]

Well ya had me looking the cover over. But after reading your post I see what you mean. I'd like to find a site that has the history of itin more detail.

I have used concrete roadbed for over 14 years. I love it.

Anyway, I still have not been able to go to see it up front and personal. I have two videos of it.

My only thought, based on the black/white photo si, they have crowed it alittle much. But thats just me. I still want to go. 

[FJ and G]

thanks, rpc for clarifying. I'm not much of contributor. Just one page and that showing some mistakes I made. I'm good at mistakes.

[rpc7271]

I don't want to start an argument but I am a structural engineer working for a major national structural design firm specializing in signature bridges. The industry standard for clear concrete cover is 2".  3" If the concrete is in contact with soil. I think the main reason for this problem is the small size of the pier. Gutter drain downspouts are usually about 5". If fear of rust is a problem reinforcing rods can be ordered epoxy coated. It varies from state to state but generally anything above 4000' is built with epoxy coated rebar. The concrete itself may be weak. If I was to do it I would add a concrete strengthing addative just to be safe.

[Rastun]

It's nice to hear contributors get an advance copy of the issue with thier submission.

If nothing else they've got a special copy to save or send to loved ones or something

Jack 

[Rene Schweitzer]

The October issue will be mailed this weekend to subscribers. David has an advance copy because he contributed to this issue.

[Rastun]

I didn't think the October issue was realeased until next month.

Unfortunately we don't know when the concrete there was poured or if there has been any problems happen since. Being it's in California there's a good chance it's been through an earthquake or three. Those can cause havoc in 1:1 construction just imagine what it can do to our little construction technics. 

[FJ and G]

There it is, in stark view, right on the beautiful cover; trouble!

It is a shot of the Fairplex Garden Railroad, a beautiful piece of work over 70 years old in L.A. or Lala land. I was amazed in reading about the early design of the railway, and the one black and white photo inside, captured the essense of railroading even better than the magnificent layout that replaced it decades later.

The first railway was Gauge 3, which is 2.5 inches, ties made of wood and rails from strapiron. Rolling stock and locomotives made from original blueprints by a teacher and his students; one piece of rolling stock per pupil. Why can't we have this type of hands-on, realistic training today!!!

The single track (now replaced my multitrack work) winds thru bucolic scenery and a handbuilt dairy farm, replaced now by more plastic scenery. Ah, the good old days.

Oh, I almost forgot about that little bit of trouble. Marc wrote about it in the last issue and since then, I studied up on it by reading multiple books about concrete casting and reflecting on my own work in casting concrete from unusual molds like drain pipes (see photo of one of my castings). 

In concrete work, it is important to reinforce the concrete. This usually is done with steel rebar. It is important to embed the rebar inside the cement and it should not come within about 6 inches of the outside of the concrete, for if it does, it is prone to rusting and expansion up to 3 times its volume. That according to my readings. When this happens, as appears evident in the cover shot, which shows a very nasty crack, the bridge or other structure is compromised.

A workaround would be to embed something that is not rust prone like chicken wire, in the concrete. The other thing I noticed about the bridge supports on the cover is the large holes caused by aggregates. Proper mixing of the concrete and tapping the form will help to alleviate this to some extent.