Can we use many concrete strength classes in the same slab ?

Dear Engineers,

 

I think the question is not that quite detailed, If they are asking to combine/mix a different concrete strength in the same slab, my answer is NO, there is no point in using much higher strength concrete in a slab design for a certain Mpa only, example : slab is design for30Mpa, why waste money in having more strength bearing concrete were in the design itself is more than enough.and of course its a big NO WAY to use below the specified concrete Mpa.All concrete samples will still be tested according to the specified strength, so again in my opinion it is just a total waste of Money. An engineer must not think only for the strength of the concrete but also for the interest of the clients which is cost saving.

Dear all,

 

It's a very big mistake, it's not coform to all norms.

If you want making that on diffrent slab level, why not.

But the strengt of concrette in Mpa,  must be calculate with a study office and verifying by a controler office.

 

I hope to have answered at your question.

 

Have a nice day.

Best regards.

Jean Marie 

Sure, as long as the lowest grade of concrete strength is sufficient to satisfy the design.

 

Sincerely

Dear All,

Good day,

RCC slab having various and different classifications and its depend to design occupancy code as well as residential/commercial/industrial, where we assume dead load/live load/dynamic/moving load.

Also, cement water ratio is depend on climatic condition as well as admixture utilized in ready mix.

Therefore, example all students are not equal caliber in same class.

Again its called strategy to concrete common wealth which needs to consult specialist/experienced for obtaining greater reliability through knowledge and experiences.

Regards,

Yes ofcourse why not , provided all the concrete strengths are more than required strength and the mix design of all the concrete strengths have same type of cements and admixtures

I answered your other question about the compressive strength test failure. And now I'm reading this question. I guess you have already made this mistake and this is why you have a failure. You should always keep the same strength say,30 Mpa , because if you have a higher one. It is not cost-effective, it will cost more, and a  lower one may not reach the compressive strength test mpa in the words of a professional if you have already make this mistake, you better look for a new job

 

question is not detailed as it may vary depending on circumstances.. for eg.

1) Its normal practice to use different grade for various element casted with slab, i.e beam, column.

2) If it is about mixing different grade while concrete is not set or hardened.. in that case it will be a big NO.. because diffrent grades may have different admixture, may have different setting time so such risk should never be taken.

3) if one pour is already done and you want to cast some other portion on other day, and if certain grade is not available, sure you can choose any other higher grade than required, make sure that proposed concrete mix is already approved with your client or try to get an approval for same