| Author |
Message |
Dale Hurttgam, NCARB, AIA,LEED AP, CSI
Senior Member
Username: dwhurttgam
Post Number: 105
Registered: 10-2005
| | Posted on Monday, September 24, 2012 - 10:13 am: |    |
Revisiting a thread from 2008 regarding fly ash in concrete slabs scheduled to receive finish flooring products.
With the ever increasing demand for sustainability and meeting LEED credit requirements, there is concern with allowing fly ash content in floor slabs that will be receiving floor finish products.
Presently our concrete specs do not permit the use of fly ash in floor slabs that will be receiving a finish flooring material, epoxy, VCT,resilient sheet flooring,carpet, etc. Fly ash is allowed for structural concrete in foundations.
I found one more recent article that suggests that a maximum of 15% fly ash content be maintained for floor slabs - it indicates that this is the threshold beyond which problems with adhesion may begin.
Potential problems include:
1. Surface strength of floor surface may not be uniform.
2. Problems with adhesive bond.
3. Longer cure time for floor slab.
4. Potential need for special surface preparation at significant cost.
Curious if others have been allowing fly ash content in floor slabs, limits on amount of content and any problems encountered with finish flooing adhesion.
Your input will be appreciated as always. |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 338
Registered: 12-2006
| | Posted on Tuesday, September 25, 2012 - 01:49 pm: | |
Dale, this is an interesting article - http://www.intertechflooring.com/PlantServices-FlyAsh_1006.pdf that points out a few very useful items:
1. Adhesion of most flooring systems is based on mechanical adhesion, not chemical;
2. It's hard to stick to silicone-based compounds; and
3. High alkali compounds can wreak havoc on your adhesive.
Essentially surface prep is critical and having a good surface profile can help overcome many problems.
Have you considered granulated slag instead? Same LEED credits and it lightens the color of the concrete when left exposed. Fly ash darkens the concrete. |
Brian E. Trimble, CDT
Senior Member
Username: brian_e_trimble_cdt
Post Number: 63
Registered: 08-2005
| | Posted on Tuesday, September 25, 2012 - 09:18 pm: | |
I just attended the Philly CSI chapter meeting last night and a gentleman from Ardex gave a presentation on Moisture Control in Concrete. Dave Stutzman asked him that exact question (Dale, were you talking to Dave?  ). Anyhow his answer went along the lines as to, yes, the fly ash could have an impact. It will depend on the amount of fly ash and the type. I can't remember what the percentage was now that he stated, but it was rather high. It was higher than the 15 to 20% quoted in Ken's article. It also affected how water moved through the concrete and the length of time for the slab to dry.
The gentleman was Bruce Newbrough of Ardex. He might have some additional information than posted here.
Another reason to attend CSI meetings! |
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