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Ferrocement Educational Forum  |  Ferrocement Discussions  |  General Discussion  |  Topic: New Report on GFRC « previous next »
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Paul Sarnstrom
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« on: April 19, 2016, 04:45:08 PM »

Hello All,

The ACI committee 549 on Ferrocement, of which I am a member, has just released the newest edition of their 'Report on Spray-Up and Continuous Strand Glass Fiber-Reinforced Concrete (GFRC)' listed as ACI 549.5R-16 in the ACI catalog.

This report should prove particularly useful to those in the GFRC industry as well as those with a general interest in the GFRC field.

Paul
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Paul Sarnstrom
daurtanyn
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« Reply #1 on: April 25, 2016, 09:41:55 PM »

Paul,

Does the report include any long term study elements? 

I've always been shy about using glass fiber in mixtures because of the risk of ASR (Alkali Silica Reaction). 

In my projects I've used PVA fibers instead.

Hubert
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Paul Sarnstrom
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« Reply #2 on: April 27, 2016, 10:51:04 AM »

Hello Hubert,

No, the report has no long term studies on the durability of Fiberglas fibers in cementitious mixtures. I suspect ultimate durability has been well tested and the results are known to manufacturers. The Fiberglas and Fiberglas type products that are made for cementitious applications are coated with zircon to mitigate the ASR issues. Hearsay says that while the zircon coating slows the ASR it does not ultimately eliminate the issue.

The GFRC industry is mostly focused on architectural detail, fascia type work - not structural work. Fiberglas fibers are used primarily as surface reinforcement to help prevent shrinkage cracking. With the exception of Fiberglas rebar, which is coated with a plastic to prevent the ASR, Fiberglas fibers are not used as structural reinforcement. The PVA fibers you mention do not have the ASR issue that Fiberglas fibers do.

On the use of fibers: Discrete fibers of any type should not be expected to or depended on to provide structural reinforcement. Discrete fibers are as their name implies discrete, not continuous. Each fiber functions as an independent unit. As such they cannot work together to provide continuous reinforcement. Fiberglas cloth or mesh [like that sold for use in the stucco industry] or any mesh be it PVA, basalt or steel is a continuous reinforcement and as such may be appropriate for structural reinforcement. Another issue with discrete fibers is that they are randomly oriented. This characteristic of random orientation works well to prevent surface cracking but works poorly in structural reinforcement work and design.

Paul
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Paul Sarnstrom
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