URGENT, PLEASE COMMENT
URGENT, PLEASE COMMENT
(OP)
i've just poured a waffle roof slab(flat) of a single family home. The beams are 6"x6" spaced 24" in both directions with 4-#3rebars and its slab is 3".
Now here comes my problem. The structural engineer specified the concrete resistance at 200kg/cm2 and they used 150kg/cm2. The structural engineer is not in town so I came here....
How critical is it?
*Attached is a JPEG
The area in red is my concern since it spans +/-14'
Everything is in centimeters.
Now here comes my problem. The structural engineer specified the concrete resistance at 200kg/cm2 and they used 150kg/cm2. The structural engineer is not in town so I came here....
How critical is it?
*Attached is a JPEG
The area in red is my concern since it spans +/-14'
Everything is in centimeters.






RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
The concrete strength specified is 2840 psi. The concrete strength used is 2130 psi.
When you say the beams are 6"x6", do you mean the overall depth is 9" including slab? Or is it only 6"?
The low strength will affect deflection. It should not significantly affect strength in bending, but it will affect shear strength.
Best plan is to wait for the engineer to return and give you his opinion.
BA
RE: URGENT, PLEASE COMMENT
www.PeirceEngineering.com
RE: URGENT, PLEASE COMMENT
No, they just pour it today but it has accelerator. Why will it be an issue in the long term? What can be done about it now? I don't want to waste 407ft3 of concrete....
RE: URGENT, PLEASE COMMENT
"What can be done about it now?"
Regardless of what the specification requires for curing - start a "traditional" wet cure NOW. Keep the concrete CONSTANTLY wet with sprinklers, soaker hose, burlap, Burlene, etc. At least this step will make the the 150 kg/cm2 concrete be its best.
www.SlideRuleEra.net![[idea] idea](https://www.tipmaster.com/images/idea.gif)
www.VacuumTubeEra.net
RE: URGENT, PLEASE COMMENT
Correct, the overall depth is 9". I've attached the file separately.
Let me clarify, it has already been poured, by the time he comes back it will be cured since is has accelerator...
If it's a major issue I rather remove the concrete NOW while I can.
RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
www.SlideRuleEra.net![[idea] idea](https://www.tipmaster.com/images/idea.gif)
www.VacuumTubeEra.net
RE: URGENT, PLEASE COMMENT
Follow SlidRuleEra's advice and wait for the engineer.
BA
RE: URGENT, PLEASE COMMENT
BA
RE: URGENT, PLEASE COMMENT
1-I know because I order it myself.
2-yes, they will remove it based on my word.
I already got hold of the engineer, I am waiting for his response.
RE: URGENT, PLEASE COMMENT
It never pays to rush into things until you have had an opportunity to review all aspects. There may well be a method of strengthening the most critical area (shaded red) after the concrete sets.
BA
RE: URGENT, PLEASE COMMENT
Going back to your question regarding the slab, sorry, it's 6.5" overall.
Thanks to you all. I will keep you posted.
RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
SRE... you may have to be careful about holding back some of the funds... in many jurisdictions, this has to be in agreement with the Contractor. In some jurisdictions, the only manner in which funds can be withheld is for the engineer to reject that portion of the Work outright.
Dik
RE: URGENT, PLEASE COMMENT
Absolutely, if there´s an issue, I leave finger pointing aside and focus on resolving the matter. We all make mistakes, the problem is the cost associated with it. This is a great forum and I am very fortunate.
Answering to Dik:
Yes, wet curing is currently in the works and yes, shoring is not going anywhere.
Regarding your second comment, it´s not a concern first because I am in Mexico and second because I am the one in charge of construction. Nevertheless, thanks for your advise.
RE: URGENT, PLEASE COMMENT
Usually it takes the stark choice between material replacement or negotiations to convince the Contractor that he can not disregard the specification, intentionally or accidentally, without (financial) consequences. Am happy to say that no contract that I've helped settle has resulted in legal action or arbitration. Also, the vast majority of the time, the Contractor would bid on and be awarded future projects - he must have been treated fairly during negotiations or we would not have heard from them again.
www.SlideRuleEra.net![[idea] idea](https://www.tipmaster.com/images/idea.gif)
www.VacuumTubeEra.net
RE: URGENT, PLEASE COMMENT
With many contracts, the only way to 'technically' deal with it is to reject it outright... they often don't have anything between 'accept' and 'reject'. My response was only cautionary.
Dik
RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
I'm not sure what commonly occurs where you're at but I'd hope you could expect high enough breaks.
To eas you mind somewhat, ask the mix provider to provide you with some of their historic test breaks(past jobs) for that mix. It can perhaps alieviate some concern if they typically are breaking higher than 200 kg/cm2
Boyd
RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
RE: URGENT, PLEASE COMMENT
He explained the Kilogram difference of cement in the mixture between the 200kg/cm2 and the 150kg/cm2 is only 5kg.
Thanks all of you that took the time to post.
-Andre
RE: URGENT, PLEASE COMMENT
BA
RE: URGENT, PLEASE COMMENT
Sorry, but I would not rely on that type of test. Get appropriate testing done or if samples were taken, wait for the 28 day results.