Replies

1. 
   Matt | Oct 28, 2006 06:00pm | #1

   Consider this just a "bump".  It's a great question though, and I am anxious to see some answers.

2. 
   Reg | Oct 28, 2006 06:00pm | #2

   Here goes.

   1) Aluminum reacts chemically with the alkaline constituents of the concrete and generates hydrogen gas. That is why aluminum powder is added to cement or mortar that you want to expand to tightly fit a space - the gas causes expansion.

   2) Since aluminum is subject to attack by alkalines it should not be allowed to come in contact with wet concrete or mortar. If aluminum in contact with concrete (or even other metals) is subject to wetting (as would happen outdoors), the aluminum should be insulated from the concrete, mortar, or metal by coating the aluminum with asphalts, bitumens, sevaral coats of paint, etc.

   The above are from the Building Construction Handbook ( McGraw-Hill), and Concrete Manual (U.S. Dept. of the Interior).

   Of course we all know that aluminum is popular because it is  inexpensive, easy to work with, resistant to most corrosion, and (a priority for some, I fear) will last for the one-year warranty requirement (even when in contact with wet mortar or concrete) common in most states.

   Hope this helps. Randy

   
   

   ---

   Edited 10/28/2006 12:19 pm ET by Reg

1. 
   davidmeiland | Oct 28, 2006 07:49pm | #3

   Thanks for the info. Are you familiar with Schluter termination strips used in tile installs? They are aluminum and are embedded in thinset mortar and grout. In shower applications I would assume these are damp. Why does this work? (Or maybe it doesn't....)

1. 
   Reg | Oct 29, 2006 12:37am | #4

   Sorry - can't help regarding Schluter Termination Strips. Also reviewed: Tile Council of America Handbook, Setting Tile (by Michael Byrne), Graphic Guide to Interior Details - no mention of aluminum being used in shower installs and nothing in the illustrations.

   Randy 

1. 
   davidmeiland | Oct 29, 2006 01:00am | #5

   Funny you should mention Michael...

   http://forums.jlconline.com/forums/showthread.php?t=33517

    

2. 
   ponytl | Oct 29, 2006 01:28am | #6

   i think alot of the alum you see used around showers is anodized...  which gives a level of protection

   p

3. 
   Hazlett | Oct 29, 2006 02:02pm | #7

    david,

    I am sure someone will be along shortly to tell you i am full of beans--or whatever.

    what I can tell you is that HERE---( akron, ohio) I routinely used painted aluminum flashing on masonry chimneys. the chimneys are typically 80 years old. usually i am replacing a roof 20-30 years old---complete tear-off----and the last chimney flashing being torn off is Aluminum. In these situations I have NEVER found any situation where the flashing had deteriorated in contact with the chimney. NEVER---EVER.

   this might be diferent---in say a sea-side climate--- I don't know--- that's not a concern for me.

   It also might be different in an application where  mill finish aluminum is embedded in wet mortar---again  Not a factor here

   ( although I have personally encountered one chimney from the '60's done that way---and the flashing was so solid it had to be ground out of the  mortar joints)

    David------ i suppose i have been just lucky--- but if so, i have been lucky between 2,000 and 3,000 consecutive times.

    I can only relate what I have personally experienced---and I readily accept that other people may have had  other experiences

   also--keep in mind--- I have  a specific life span in mind. when we do a roof--- I am designing for a 25-30 year life cycle. I want everything to last for at least 25-30 years---and ideally it will ALL fall apart at the same time LOL. nails, caulk, flashing , shingles---all comparable. in the rare cases we use a more durable material ---like 50 year shingles---we generally try to use copper.

   since we fully expect that chimney flashing on a 30 year roof to be torn off and thrown away 30 years from now---we plan accordingly. If we were doing a slate roof we wanted to last 100plus years---we could plan appropriate materials for THAT projected life span as well.

   that's all I can tell you,

   Best wishes,

   Stephen