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Strengthening of Concrete structure after construction
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sivavadivelan
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PostPosted: Thu Jun 28, 2012 11:12 am    Post subject: Strengthening of Concrete structure after construction Reply with quote

Dear Experts,


As per design the grade of concrete required for the Pedestal of a Boiler foundation in one of our project is M25. But the Compressive strength of concrete cubes at 28 days were not satisfactory as per IS 456.

We have conducted rebound hammer test and Ultrasonic Pulse velocity Test on the structures and the average result of the tests are as follows,

The average compressive strength of the structure is found as 15 N/mm2 and the as UPV the velocity is between 3 to 4 km/sec.

As per our Design consultant the actual stress in the foundations are from 13 N/mm2 to 19 N/mm2.

Can you please advise me on this to proceed further? Is there any possible ways to strengthen the concrete structure without demolishing the concrete?

Regards

SIVAVADIVELAN M
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suraj
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PostPosted: Thu Jun 28, 2012 11:28 am    Post subject: Remove Concrete Reply with quote

Eng SIVAVADIVELAN M

In this case, sooner better, remove this concrete since M 15 is not used even for blinding on facilities. Save time.

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IntPE(India)Suraj Singh FIE Civil
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sivavadivelan
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PostPosted: Thu Jun 28, 2012 12:02 pm    Post subject: Reply with quote

Dear Suraj sir,

Thank you for responding, But the client is refusing us that the structure should not be dismantled.

More over the mechanical erection have started over the foundations.

Regards

Sivavadivelan M
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suraj
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PostPosted: Thu Jun 28, 2012 5:36 pm    Post subject: Boiler Foundation Reply with quote

Sivavadivelan M

Boiler Foundation
Could you please, attach all details about foundation, its surrounding interfaces & limitations governing this vessel.
Probably, dimensions adjustment may possibly be effected.

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Natabar Sumatsingh
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PostPosted: Thu Jun 28, 2012 6:17 pm    Post subject: Re: Strengthening of Concrete structure after construction Reply with quote

sivavadivelan wrote:
Dear Experts,


As per design the grade of concrete required for the Pedestal of a Boiler foundation in one of our project is M25. But the Compressive strength of concrete cubes at 28 days were not satisfactory as per IS 456.

We have conducted rebound hammer test and Ultrasonic Pulse velocity Test on the structures and the average result of the tests are as follows,

The average compressive strength of the structure is found as 15 N/mm2 and the as UPV the velocity is between 3 to 4 km/sec.

As per our Design consultant the actual stress in the foundations are from 13 N/mm2 to 19 N/mm2.

Can you please advise me on this to proceed further? Is there any possible ways to strengthen the concrete structure without demolishing the concrete?

Regards

SIVAVADIVELAN M


Have you checked the IS codes?
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spsvasan
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PostPosted: Sat Jun 30, 2012 3:35 am    Post subject: Reply with quote

Dear Er.Sivavadivelan

If the footing concrete is satisfactory, it may be sufficient to provide a jacket (an outer layer of reinforced concrete) to the pedestal. A thickness of 150mm will probably be sufficient, but it has to be checked with reference to required strength, cover, and concrete pourability.

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S.P.Srinivasan
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suraj
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PostPosted: Sat Jun 30, 2012 5:23 am    Post subject: Boiler Foundation rejected concrete Reply with quote

Dear Eng
<A>Natabar Sumatsingh
Boiler Foundation rejected concrete
You have not provided additional feed back.
Hope you have resolved issue.
It seems that your boiler is not an auxiliary but main one.
In case, no resolution has been reached, provide requested details.
Remember that intefacets are significant in such facilities cases that may not be known at this stage.

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Purti
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PostPosted: Sat Jun 30, 2012 6:47 am    Post subject: Re: Strengthening of Concrete structure after construction Reply with quote

Dear Engr SIVAVADIVELAN M,

Kindly attach sketch of foundation detail and boiler detail.

As per my opinion,
check design(require size and reinforcement) with M15 grade of concrete.

Strengthen it with extra require size and reinforcement(as per design M15 grade of concrete) with M25 grade of concrete.

Regards,
Purti Thakkar
Design Engineer
SAI Consulting Engineers Pvt. Ltd.



sivavadivelan wrote:
Dear Experts,


As per design the grade of concrete required for the Pedestal of a Boiler foundation in one of our project is M25. But the Compressive strength of concrete cubes at 28 days were not satisfactory as per IS 456.

We have conducted rebound hammer test and Ultrasonic Pulse velocity Test on the structures and the average result of the tests are as follows,

The average compressive strength of the structure is found as 15 N/mm2 and the as UPV the velocity is between 3 to 4 km/sec.

As per our Design consultant the actual stress in the foundations are from 13 N/mm2 to 19 N/mm2.

Can you please advise me on this to proceed further? Is there any possible ways to strengthen the concrete structure without demolishing the concrete?

Regards

SIVAVADIVELAN M
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sivavadivelan
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PostPosted: Sat Jun 30, 2012 2:17 pm    Post subject: Details of foundation attached Reply with quote

Dear Suraj Sir, Srinivasan sir, Purthi ji

Thank you very much for your valuable comments. The details of foundation are as follows


The Boiler is Auxiliary Boiler of Capacity 100 TPH, the boiler is mounted over tie beam interconnecting 8 Pedestals. I have attached the Sketch of the plan arrangement, C/S of Pedestals & Cross sectional Elevation details of Foundation here with my posting.

As per design requirement the Plan sectional arrangement of Pedestals & Beam has limitation and the C/S of the pedestals can be modified.



Regards


M.Sivavadivelan



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Boiler Foundation Pedestal Cross section Details.pdf
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Cross Section Details of Pedestals

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Boiler Foundation Section.pdf
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Section arrangement of pedestals and Tie Beams

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Boiler Foundation Plan.pdf
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Plan view of Foundation Arrangement

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P.K.Mallick
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PostPosted: Sat Jun 30, 2012 4:52 pm    Post subject: Re: Strengthening of Concrete structure after construction Reply with quote

sivavadivelan wrote:
Dear Experts,


As per design the grade of concrete required for the Pedestal of a Boiler foundation in one of our project is M25. But the Compressive strength of concrete cubes at 28 days were not satisfactory as per IS 456.

We have conducted rebound hammer test and Ultrasonic Pulse velocity Test on the structures and the average result of the tests are as follows,

The average compressive strength of the structure is found as 15 N/mm2 and the as UPV the velocity is between 3 to 4 km/sec.

As per our Design consultant the actual stress in the foundations are from 13 N/mm2 to 19 N/mm2.

Can you please advise me on this to proceed further? Is there any possible ways to strengthen the concrete structure without demolishing the concrete?

Regards

SIVAVADIVELAN M


I have some basic questions here.
1)In case of rebound hammer test did you follow the procedure of obtaining  correlation between compressive strength of concrete and rebound number described in IS 13311(PART-2)?
2) Velocity of 3 to 4 km/s keeps the quality of concrete in a range of medium to good. Usually the assessment of compressive strength of concrete from UPV test is not adequate. How you derived average compressive strength as 15N/sqmm?
3) Why do not you go for core test ? you can have rebound hammer on core and then subject the core to compression test to establish relation between compressive strength obtained from rebound hammer and   compression test.
4) What are your cube test results?
Warm Regards.

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