I just built a stone wall with illuminated glass features embedded, and to make them shine evenly, I had all sides but the visual one wrapped in industrial thickness aluminium foil. One week later, the foil has disintegrated. I have used type 10 Portland. What is going on?
I believe your problem is that concrete acts as a fairly strong base (this is especially true of mortar mixes). It is well known that strong base will react with an active metal like aluminium and produce hydrogen gas as a byproduct. The representative reaction is: 2Al+6NaOH==2Na3AlO3+3H2, This reaction is fairly rapid and can even cause an explosive buildup of hydrogen gas in a non-ventillated area.
Embedded aluminum roof flashing, aluminum water stops, aluminum electrical conduit, introduced aluminum powder (sometimes used to foam concrete), or embedded structural aluminum shapes may all corrode in concrete or mortar. In all cases, a reaction that forms aluminum hydroxide and hydrogen gas occurs, and may cause expansion and cracking of the concrete or mortar. The common use of calcium chloride (or other alkali compounds), and dampness of the concrete increases the reaction rate. Usually, coating the aluminum with bituminous paint, impregnated paper or felt, plastic, or an alkali-resistant coating will prevent or sharply reduce the corrosion.
