Detailing Rebars in Pour Strips

[Robbiee]

Typically rebars are spliced in the pour strips in suspended slabs. If rebars are NOT spliced, i.e. continuous, and the concrete is poured after 28 days from pouring the adjacent panels, is that any helpful for releasing shrinkage stress?
Thanks for the input.

 

[civilperson]

Yes the shrinkage stress in the second placement is lessened by the % of the dimension already placed compared to the overall dimension.

 

[Robbiee]

Civilperson,
Thanks for the input. I did not understand from you if the rebars being continued across the pour strip vs. being lap spliced will affect the purpose of the pour strip.

 

[hokie66]

Continuous bars and properly lapped bars are treated the same in slab design, so there would be not difference in your case.

While delay between pours is beneficial in controlling shrinkage in the longitudinal direction, in the opposite direction, shrinkage of the second pour will be restrained by the first pour and will likely result in some restraint cracking.

 

[Robbiee]

Yes, the pour strip will be poured 28 days after the adjacent panels are poured. Now, is it OK to make the rebars continuous through the delayed strip? To me this delaying is only a waste of time and is only serving similarly as the saw cuts; controlling where the cracks to happen. I could not convince the boss here that rebars must be lap spliced in the pour strip.

 

[hokie66]

Ailmar,

I am sorry, I didn't fully understand your question at first. I thought you were comparing placing the slab with just constructions joints with continuous reinforcing vs. with delayed pour strips with lapped bars. Now I see you are talking about using pour strips, but with continuous bars.

Certainly the continuous bars would provide some restraint to the second pour, while lapped bars would not. So the second slab would tend to crack more. How much more and whether the cracking is important would be dependent on the structure.