Topping Bond Strength on Precast Double tees

[ajk1]

What minimum bond stregth should I specify for a new parking garage, for the cast-in-place concrete topping that will be poured on top of the new precast prestressed double tee units that will have a deliberately roughened surface? I believe that CSA A23.1 gives a minimum bond strength for toppings of 1.0 MPa (145 psi) but I was wondering if anyone has experience with this, what bond strength is generally obtained when the topping is placed on deliberately roughened tees, and whether I can specify something > 1.0 MPa (perhaps 1.5 MPa) without encountering push-back from the contractor. A greater bond than 1.0 MPa might be desirable, given that this is a roof level open air parking subject to the full summer to winter temperature variation of minus 20 deg. C to plus 35 deg. C in this area.

Also, is there any surface prep required beyond the deliberately roughened surface and a saturated surface dry condition before placing the concrete?

Is any bonding agent used, such as a rich cement slurry scrubbed into the surface of the roughened tee? I think not, but I am not sure.

 

[dik]

agreed hokie... but other than scope, I cannot explain why it was missed... I worked for the one for a decade and they were right up with reinforced concrete, parking garage design and corrosion issues... one of the better firms in Canada... I've done consulting work for two of the others and they were well versed in deterioration... and Ron can speak for Trow... another bright light... Other than scope, I cannot explain why this was missed.

Dik

 

[hokie66]

Maybe it was a bit far to drive from their main offices, and they didn't send the people with the required experience? Just thinking, I don't know.

 

[Ron]

Trow did a credible condition assessment in the early 90's and made recommendations for repairing the leaks then as well. Not sure if anything was done per their recommendations. Their opinion of cost for the repairs at that time was over 1.2 million CDN.

Trow was/is a high quality group (now exp consultants). Not sure of their exposure in this one.

 

[BAretired]

Sometimes it feels good to be retired.

BA

 

[Ron]

BA...You are a smart man!!

 

[hope9010]

Hi dik - where exactly did you read that the hollow core was over-spanned? I cannot recall reading that in the reports.

 

[dik]

Hokie... haven't forgotten, just so busy... will try to reply later today.

Dik