Q 1. Can ES600 be used in seismic area cat. B?

Yes

ACI 318 imposes restrictions on special seismic systems in seismic categories C, D, E, and F. Thus, using ES600 shall be safe in seismic category A & B.

Q 2. Where are the best elements to be reinforced with ES600 which will give the most savings?

Elements that are controlled by flexure or tension stress such as. Foundation, Slabs, beam, and tension element (ties) will give the most savings.

Q 3. Can ES600 be used in the intermediate frames? What is the limitation of strength for rebar for the intermediate frames?

Yes. 

According to AC525 clause 1.21.1 “does not permit the use of intermediate high strength steel grade 90 (ES600) in the longitudinal bars of special moment frames, special structure walls boundary elements and coupling beams in seismic design category D, E & F” . However, according to ACI 318 -19 Footnote no. 4 table 20.2.2.4 (a) limits the fy of the longitudinal bars of intermediate moment frames to 550 Mpa 80 Ksi.  It is good to mention that not all frame elements in a structure should be designed as moment intermediate frames unless they are designated structure elements and part of the lateral stability system of a moment frame system or dual system. 

Q 4. Is it allowed to use more than one rebar grades in same project similar to cement?

Yes, nothing in the code prohibits such use.  

However, the execution team and building inspector need to ensure good QAQC practice.

Q 5. Is it allowed in the code to mix 2 different grade rebars in the same element?

Yes. According to ACI 318-19 table 20.2.2.4 (a) it allows using different rebar grades in the same elements such as boundary elements confinement and spandrel beams diagonal rebars to reduce the rebar congestion.

Q 6. Can ES600 used for full building or just only the few floors at lower where the load and congestion are very high?

ES600 can be used in specific elements or specific floors. See answers to Q # 4 and 5

Q 7. Can we do splice joint between ES600&B500B? which rebar grade will define the lap length?

See ACI 318-19 Section 25.5.2.2: If bars of different size are lap spliced in tension, lst shall be the greater of ld of the larger bar and lst of the smaller bar.

Q 8. Is the development length / lap splice for ES600 same as B500B?

No, it is around 20-30% higher. AC 525 clause 4.1.4 Recommendation should be followed.

Q 9. When designing for columns, the design considering that column is under tension & compression forces, so the limitations will be 550 MPa, please confirm?

550 Mpa limitation should be considered only for load combinations that are causing compression stress on columns which is the most common case. However, in cases that are column design is governed by tension stress 600 Mpa can be used.

Q 10. Can we use same couplers being used for B500B or do we need high grade coupler?

Higher couplers are required and the AC133 quality control program should be followed in accordance with AC525 clause 5.2.

Dextra and Lenton have confirmed that their couplers commonly available in UAE can be used for ES600.

Q 11. What is the max length of straight rebar can be supplied by Emirates Steel for ES600?

12 m

Q 12. Is it required to use self-compact RC or normal RC or precast?

No special requirement for concrete. The only requirement for a minimum fc’ according to table 19.2.1.1 ACI 318 -19 of should be followed.

Q 13. What is the max grade of concrete to be used?

No Limitation actually it is recommended to use high-strength concrete with high-strength rebars Can we use ES600 for post-tension slab & prestressed?

Yes, nothing in the code prohibits the use of high strength rebars in post-tension slabs

Q 14. Can we use ES600 for Bridges?

Yes, However, specification is not within the scope of AC525. Will depend upon the bridge spec being used.

Q 15. Can ES600 be used in piles?

Yes, However, the current acceptance criteria from ICC (AC525) is for building application only. Piles are used to support buildings. So they are within the scope of the 2021 IBC and AC525.

Q 16. What are the fatigue values of ES600 comparing to B500B?

Fatigue testing has been done and fatigue properties of ES600 are comparable with B500B. ie : No failure until 1 Million cycles.

Q 17. Is the rib pattern of ES600 different than B500B?

Yes, Please see AC525 & ESR-4800

Q 18. How can we identify physically ES600? Is there any marks different than B500?

Below photographs clearly show the difference in marking between B500B and ES600.