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Old 05-14-12, 09:53 AM   #38
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Originally Posted by lucerne96 View Post
According to this

an article from the 4th Int Symposium on Roof Technology; Re use of fly ash in shingle manufacture:

"A common specification among shingle manufacturers is a limit to the free lime content in filler. Roofing industry experience has shown that an excess amount of lime can react with certain asphalt constituents to greatly accelerate granule loss from the shingle, resulting in premature failure of the roof."
The paragraph above refers to excess free lime in the finely pulverized mineral stabilizer filler used in the interior of the shingle during the manufacturing process. Filler is used inside the shingle to keep the asphalt from flowing when it gets hot on the roof. That article proposed using fly ash as replacement for the pulverized limestone traditionally used as filler. It isn't referring to the much larger sized grit imbedded on the surface of the shingle.

What I am doing involves just the upper exterior surface of the shingle. The granules on composition roofing are usually made of limestone (calcium carbonate), which is what hydrated lime turns into as it cures. I'm just adding a thin layer of unpigmented (white) limestone on top of the pigmented limestone grit that is already there. Calcium hydroxide has long been used as an additive to the asphalt used for paving roads to make pavement last longer.

Fly ash is a mix of silicon dioxide, aluminum oxide, and iron oxide, which chemically is very different from the calcium hydroxide in hydrated lime.

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Last edited by basjoos; 05-14-12 at 09:57 AM..
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