Rebar yield Strength & Grout vs Concrete 1

[struggle66]

Hi Good Day Everyone,

I've got a few question. Hope you guys can help me out.

(1) Now in Singapore we are using Euro codes which means fy = 500 MPa. Before we used BS8110. Now the main contractor wants to use fy=460 MPa rebars for some reasons for a project designed to EC2. If so, I would like to know what are the implications?

(2)my second question is once there are cracks or concrete defects (non-structural), normally people will hack or trim the concrete & grout back. But since there is no aggregate in the grout, what will happen? They use the grout which has the same compressive strength as concrete.

Thanks

 

[allgoodnamestaken]

Every structural element will have to be assessed again to consider what their new capacities are. Will the savings in using cheaper rebar (which I assume you've checked conforms to your structural code) offset all the redesign costs?

 

[jike]

Grout is probably OK in direct compression but not so good to carry shear. It is my understanding that the large crushed aggregate helps carry shear. Grout manufacturers generally require including aggregate for thicknesses greater than 3 inches.

Of course, the effect of exact loading conditions should always be evaluated.

 

[rapt]

Eurocode 2 actually defines reinforcing steel strength as 400 - 600MPa in Annex C.

Standard bars are 500, but any strength bar within that range can be used. If the bar strength is 460, you will need about 500/460 more reinforcement.

 

[struggle66]

rapt,

Thanks for your info. I was just wondering if there are any figures or specifications in EC2 that derived based on 500 MPa. Since EC2 does specify the steel strength range 400-600, then that should be alright & of course more number of reinforcement.

jike,

Thanks. Shear is what I was thinking too.

Allgoodnamestaken,

Thanks. The reason is contractor has got stock piles of 460 MPa rebar.

 

[podosci]

The 460N/mm2 is the steel strength of a particular bar,and when used in design it would produce the required steel area for that class of strength... Like in Nigeria, it's 460N/mm2 that's readily available so we tend to use it in all our designs except for special placed orders from the steel manufacturing companies.