[Q&A]: Is it also compulsory to soak Steam Cured Fly-Ash Bricks in water before using it?

Query received from Mr. Sandip S. Mohite, a resident of Goa, India via the comments section of the earlier posted article here on bricks-n-mortar.com, titled: "Brick Masonry work | "Why bricks be soaked in water before placing them?"

His query is shared herewith so that other interested people reading this blog may also have insight in this respect and may participate in an e-discussion on this topic, if deem so. The query being..

Image source: brickmasonry.in
Is it compulsory to soak Steam Cured Fly-Ash Bricks in water before using it?
These Fly-Ash Bricks are not porous like clay bricks, they are machine made & hydraulic pressed, even water absorption of fly-ash bricks is between 8% to 13%, still is it required to soak the bricks in water?

Please guide me regarding the same & do we have any I.S. Code for Fly-Ash Bricks? Please confirm.

Thanks with regards.
Sandip S. Mohite

Posted as 'Anonymous' to BRICKS-n-MORTAR.com at Thursday, January 19, 2012 11:15:00 AM GMT+05:30
BricksnMortar Edesk replies...

Dear Mr. Mohite,

The primary purpose of soaking the masonry building blocks is to negate the possibility of them blotting and sucking out the moisture/ water from the mortar that is used to bind them. No matter if they are clay bricks, or fly ash bricks, or autoclave aerated concrete blocks, or hollow/solid concrete blocks-- all of them should ideally be soaked in water. This ensures that the masonry units do not suck / steal away the requisite water from the cement-sand mortar, and thereby not make the mortar brittle/ weak and the strength of the mortar joints be weakened as cement would not provide the requisite strength in that case.

But, one thing that should be handled CAREFULLY is the TIME OF SOAKING for different kind of masonry units, which shall primarily be guided by the respective absorption factors (%age weight increase when water is absorbed by these masonry units). The soaking process should be timed so that the minimum levels of absorption are achieved and NOT the maximum levels since the weight of individual units would increase in the latter case, thereby making their handling by workmen relatively difficult as compared to dry ones.

Soaking of man-made masonry units has one more advantage--
the process may help recognizing harmful efflorescence effects in individual units and/or lots of masonry units (bricks/ blocks/ etc.) that if not identified beforehand, may prove deleterious aesthetically in due course of time.

Coming back to your query, your mentioned 'steam cured, machine made, hydraulically pressed fly ash bricks' should ideally have relatively lower water absorption ratio as compared to normal autoclaved fly ash bricks. We suggest that you get a few samples of these bricks tested for water absorption and then decide upon the time period of water-soaking depending upon the test results for optimal moisture ingress in them before laying them in masonry coarses.

As regarding the Indian Codes and Standards of practice for fly ash bricks, a few of them are furnished hereunder for your ready reference:
  • Indian Standard - IS: 13757-1993 - (Burnt clay fly ash building bricks – Specification)
  • Indian Standard - IS: 12894-2002 - (Pulverized fuel ash-lime bricks – Specification)
  • Indian Standard - IS: 2212-1991 - (Code of practice for brickworks)
  • Indian Standard - IS: 2222-1991 - (Specification for burnt clay perforated building bricks)
  • Indian Standard - IS: 1077-1992 - (Common burnt clay building bricks - Specification)
  • Indian Standard - IS: 11650-1991 - (Guide for manufacture of common burnt clay building bricks by semi-mechanized process)
Besides the aforementioned Indian Standards, the usual American ASTM Standards for clay bricks, viz., C62, C67 and C216 also do hold good for flay ash bricks also.

Hope this information suffices to your query. Should you have require any further or other information, feel free to contact us.

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  1. I fully agree with bricksnmortar edesk. I should soak all kind of masonary bricks or blocks before placing them at site of work.

    I did a paper on this in my college project and found out that no matter if the blocks are autoclaved and cured or not, still they absorb substantial amounts of water in their dry state.


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