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[ajay84]

Hello,

In absence of specific Indian standard w.r.t Concrete Cover Blocks/ Spacers, there is ample ambiguity among manufacturers, users & testing agencies.

As per IS 516, the normal rate of loading is 140 kg/sq.cm/minute for a 150X150X150 cube. I would like to know whether a concrete cover block as small as 50cmX25cmX25cm can also be tested with similar methodology to regular cubes.

Please throw some light.

Thank you.

Regards,

Ajay.

[Dr. N. Subramanian]

Dear Er Ajay

I do not think there is a prescribed test method for concrete covers in any code, leave alone IS 456.

The cube testing procedure will not be applicable to concrete cover blocks.

Moreover, for cover Block, more that compressive strength, durability is important. You may note that even in regular concrete getting the desired strength is not that difficult. If the design mix is M25 you will easily get more than M25 in most of the cases. But getting the durability is not assured. That is the reason why fly ash and other additives were recommended.

Warm regards
Subramanian

[vikram.jeet]

CONCRETE cover blocks

For Building construction works ,their  strength is not any issue , nor it's permeability. But for water retaining structures , cover blocks cover the reinforcement at locations these are placed during execution , and needs to be durable / impermeable to protect initiation of  spot rusting of reinforcement.

Generally these are cast with richer mix than parent concrete .

[sspawar]

Dear Sefians,

In most of the valuable/Important projects - specifications for cover blocks are mentioned and elaborated well in the contracts.

Though there is no specific IS standard for testing cover block but It is desired and be mentioned in the quality plan of the projects that strength of cover blocks must be equal to the strength of concrete mix.

Quality plans describes well whether it should be site made or factory made , how would be tested. what will be the procedure for maintaining the quality.

Concrete blocks never be made of mix as of concrete which is used for structures.

Concrete blocks are generally designed and tested and approved  as  contracts describe.

Concrete blocks are generally made of mortar with finer aggregates with richer mix and additives.

Concrete blocks testing cubes are generally filled as of cement or mortar cubes.

Since site made blocks quality can not not be controlled as well as factory made and branded blocks, hence factory made made blocks are more preferred.
Sizes and varieties and making material varieties are also possible with long range from factory made products.

Third party test is commonly adapted for quality checks and control.

Standards are generally refereed as BS 7973-1 and 2 and IS 4601 and 2185 and 15658.

A manufacturer's catalog -power point is attached here for more idea regarding what is being practiced in India and abroad.

Though it is true that durability can not be ascertained as it requires a historical records and series of experiment and tests.

Regards