Stayform as a replacement for intentionally roughened surface on construction joints.

[ggcdn]

Contractors often request to use stayform at construction joints, and I've heard from both engineers and contractors alike claim that it alleviates the need for an intentionally roughened surface or keyways.

However, I can't seem to find any justification for those claims.

Anyone have thoughts on this, or even better, anyone know of testing to prove it?

-JA
try [link calcs.app]Calcs.app[/url] and let me know what you think

 

[Aesur]

I have heard this and seen it used a few times as well. Their own documentation says it's considered "roughened" and therefore additional roughening is not required, I assume they would have testing for this? Link

I'm not sure I buy that it meets the normal 1/4 amplitude though. It appears that it only achieves 303.9 psi shear bond strength at 28 days according to the link above.

 

[ggcdn]

Thanks for the link. Those test results leave a lot to be desired. They don't mention the test setup, and the amount of reinforcing crossing the joint is going to greatly influence the stress.

If I were to assume the tested plywood condition as 'not roughened', I would expect to see a 1.66 increase in bond strength for stayform to perform as good as 'intentionally roughened' (since the friction factors in ACI are 0.6 and 1.0 respectively). But this is saying the increase was only ~20%.

So at least I can point to this as some evidence that it is not a suitable replacement for intentional roughening.

-JA
try [link calcs.app]Calcs.app[/url] and let me know what you think

 

[HTURKAK]

I did not compare the properties of STAYFORM with STREMA ..

I know this product and the resistance of construction joints with strema is not less than monolytic concrete.Stremaform in the concrete gives a rough surface that satisfies the requirements of an indented joint according to DIN 1045-1 and/or Eurocode 2 and
does not need scabbling.

I will propose to look to the following doc. for tests..

https://www.maxfrank.com/wAssets/docs/products/brochures/stremaform-formwork-elements-BR-INTGB.pdf