I suppose too much fiber mesh could cause a problem but too much water could have been the problem as well.

If the recipe was the same and the curing the same I would suspect too much water

These are pics of a sandLESS tufa container I made with LOTS AND LOTS of fiber. It is still holding up a year later.

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Marly

There are several dozen types of fibermesh.
The stuff I have is called stealth. No idea why.
It was recommended by the batch plant owner over another fibermesh they use.
I have no idea what the difference is but considering the wacky business of concrete there could be fibermesh that is wrong for tufa.:)

Reading about fibermesh makes my head hurt.
I have no idea how you would select one for tufa.

Here is a link that might be useful: Yikes!

The fibermesh I used was the one recommended in one of the posts. It is kind of hairy looking. I got it from Concrete Depot.com. It was $8.00 a lb. I bought 5 lbs, which is more than I will use in several lifetimes. A lb. goes a long way. Live and learn. Archer

I have only used the fibermesh, also from concrete depot, for straight cement/sand work. The rate of curing appeared identical and was under plastic.

I don't know why you have experienced such a difference in curing.

Archer --- Fibers have no effect on the formulation or curing. There must be another culprit.

I use fibers from the local concrete supplier, and on some of my smaller bowls I don't use them at all and have noticed no difference in curing. Sometimes I get a batch of tufa that plain old doesn't cure correctly, and I have never figured out why. I use the same formula of 3 portland, 4 peat, and 5 perlite and a handful of fibers all the time. I think it has something to do with the amount of water, but that's just a guess.

You could also have some bad cement. It deteriorates in humidity, and according to some people, with just age (and I'm not talking years).

You didn't happen to find lumps in it, and mash them to go into your mix, did you?

Sue

Thanks for all the help and suggestions about fibermesh. My troughs finally got nice and hard. I believe that It may have been too much water in the mix that slowed down the process. At any rate I am delighted that my hairy ones are now as hard as the bald ones. Archer4

OH MY GOD I SIFTED MY CEMENT BECAUSE IT WAS ALL LUMPY!!!IS THAT WHY MY TUFA CRUMBLES???

Lumpy is generally not good.
If you want to use it make a small test brick of Portland and sand and see how it is for strength the next day.
Portland is so cheap it's best to spend the $7 and buy a fresh one.

$7 is cheap for cement, but having to get it in 94 lb sacks is just too much weight for me to lug around. Would even be willing to pay the full $7 for a smaller sack--even down to 30 lbs. That would be enough for 3 good size hypertufa troughs, and I would not have to run the risk of breaking my back with a 94lb sack. Just my 2 cents worth. Archer4

It is hard to understand why places like HD don't demand smaller bags.
I agree with you, I hate those 94 pound bags. I end up sore and filty after bringing thos suckers home.

When I need another bag of portland cement, I go to HD or Lowes and drag along 2 plastic containers with lids. Some nice man opens the bag and pours it into my 2 garbage bags which I have in the 2 plastic containers. Then somebody takes the stuff out and puts it in my car. That way, when I get home I can manage the 47 pound containers. Try it!
Laura

I'm with you Laura, 94lbs is too much. I have somebody at HD load it in the back of the truck; gravity helps me get it out, and then I lay a plastic container on its side, flip the bag into it and sort of leverage it in...it is really humiliating to be outsmarted by a 94 bag of concrete...

My last trip to the supplier was 600 pounds. It was a back killer.
Stocking up on aggregates that are hard to buy here in the winter, like stucco chips and filter sand.
The cool part is I'll be able to use this material in my truck for weight during the winter as well.:)