5/17/2008
8:31:54 PM 

John,

The issue has to do with the 40% fly ash recommendation for LEEDS credits. This amount will definitely cause serious problems with all glued flooring.

The tests that are going to be conducted will determine what the safe threshold amount should be.

The 40% recommendation was obviously an arbitrary number (must have been pulled out of hat) that simply will not work with glued flooring of any type.

5/18/2008
9:50:21 PM 

If you are worried about it I would agree with Darian do a bond test and then PH and moisture testing document everything with time location of test with photos with results. We as installers are only responsable for the substrate at time of installation and I have it all documented many of times over. Question, How many job failure.s have been from Fly Ash?

FD

5/26/2008
5:40:54 PM 

FYI

The next

Concrete, Moisture and Failures Seminar is August 13th and 14th.

5/27/2008
1:57:29 PM 

Greetings!

I did not read through the four pages but the topic caught my eye. Yes, fly ash concrete is out there.

I have subscribe'd to this website for quite awhile now. It has a forum and sends you news on concrete ect.

http://www.aggregateresearch.com/forum/

5/28/2008
7:19:39 PM 

(NEW DELHI, India) -- Scientists at University of New South Wales have turned the ash waste from coal-fired power stations into a global environmental solution which promises to slash emissions in construction sector by 20 per cent. Researchers at UNSW have converted the fine particulate pollution generated in coal furnaces, known as fly ash, into a new range of high-strength, lightweight building materials.


NOTICE: Lightweight building materials.. !!

5/29/2008
1:16:46 AM 

Try posting a question in the forum. You might get repiles from all over the world.

I have read many conversations about the use of fly ah in concrete over the years.

5/29/2008
6:45:05 PM 

So what exactly is Lou Migilore and his side kick trying to say in that article? Adhesive does not stick due to the roundness or spherical nature of fly ash?

And where are these issues or failures documented?

Quote:
"The key problem with EXCESSIVE add-mixes is "Efflorescence".. this is alkali leeching out of the concrete.
"

I think a few people have their head up their fly ash.

5/31/2008
6:13:22 PM 

How about 100% fly ash concrete like the romans used?

I found this. It actually may be better than portland as far as moisture and efflorescence is concerned.

As previously described, the paste is the key to durable and strong concrete, assuming average quality
aggregates are used. At full hydration, concrete made with typical cements produces approximately
1/4 pound of non-durable lime per pound of cement in the mix. Most people have seen concrete
or masonry walls or slabs with the white, chalky surface coating or streaks called efflorescence.
Efflorescence is caused by the face of the concrete being wetted and dried repeatedly, or by the
movement of water vapor from the damp side of the concrete to the dry side through the capillaries
(voids), drawing out the water soluble lime from the concrete, block or mortar. A typical 5 sack
concrete mix having 470 pounds of cement per cubic yard has the potential of producing 118 pounds
of lime. Fly ash chemically reacts with this lime to create more CSH, the same “glue” produced by the
hydration of cement and water, thereby closing off the capillaries that allow the movement of moisture
through the concrete. The result is concrete that is less permeable, as witnessed by the reduction
in efflorescence.


And then some other interesting facts about it.


Other evidence of the contribution fly ash makes to strength and durability includes:
– Cement has an upper limit of roughly 7.5 sacks (7.5 x 94# sack = 705#) when using
1" maximum size aggregate, above which the psi per pound of cement strength contribution in a concrete
mix diminishes rapidly. The tallest concrete structures in the world are made with concrete where fly ash
is a necessary component. Its ability to contribute to additional CSH, lower water demand, reduced heat
of hydration and its fine particle size are crucial to making high-strength concrete (8,000 psi to over
20,000 psi).
– Cement was invented in 1824, over 170 years ago. There are examples on the west coast of Italy, in a
town named Cosa, where a mixture of natural pozzolans (volcanic) were combined with lime to produce
concrete that has withstood waves and attack from seawater for over 2,000 years and is still intact.
– The Pantheon in Rome is a pozzolan and lime concrete structure built around 300 B.C. and still stands
today. It features a cast concrete dome 124 feet in diameter and was the world’s largest domed structure
until modern times.

6/1/2008
3:51:01 PM 

C.mon Ray. Volcanic....natural pozzolans. More importantly the article touches on issues you and Lew were worried about. That research took me all of ten minutes. I have the pdf file if you want to read the whole shebang and who wrote it but thats gonna cost you another case of whiky whiky.

6/1/2008
7:21:00 PM 

does the fly ash have on the expansion rate of concrete?

If it hardens it does it impede expansion ?

We know concrete has the same expansion rate of steel. .008 mm per 10 ft per 10 degrees C.