CLC blocks with Fly ash only - urgent help required

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CLC blocks with Fly ash only - urgent help required

Postby dogragurjeet » Wed Apr 27, 2016 5:00 pm

Hi alex,
It's a treat to come back to this forum again and again, for the wealth of knowledge.
We are located in India and have started a CLC block making business.
We are using cement, thermal power plant fly ash, and currently using synthetic foam from GUBBI enterprises, Mumbai (we are willing to shift to protein based foam). Further we are adding Calcium chloride. We intend to steam cure the blocks. We are demolding the blocks after 24 hours, but the edges usually break off. We are curing the blocks in steam, as well as putting some blocks for water curing, just to compare the two. There are micro cracks which are widening with time in both the samples, albeit less in the steam cured blocks. The density we are targeting are 800-850 Kg/cu.m. with a strength of 2.5 to 3.0 N/mm sq. We have fairly hit these parameters with ease, but cannot control the micro cracks and edge breakage.
Please advice on two aspects 1. Ideal mix for our condition (no sand) 2. Curing methodology, keeping in mind that we will be using steam curing. (please also let us know that if we need to water cure even after steam curing, and if yes for how many days. And when should we ship out the product for application?)
The temperature here is 40-45 degrees centigrade in the daytime, and we feel the mixture is drying too fast.
Will PP fibres help in this case?
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Re: CLC blocks with Fly ash only - urgent help required

Postby dogragurjeet » Thu May 12, 2016 4:52 pm

IMG-20160512-WA0006.jpg
IMG-20160512-WA0003.jpg
IMG-20160512-WA0004.jpg

I am posting some pictures of the cured blocks. These samples developed cracks after 10-12 days and these seem to widen to some extent and then stop.
Please help. Urgently.
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Re: CLC blocks with Fly ash only - urgent help required

Postby mohammed » Fri May 20, 2016 9:24 am

dogragurjeet wrote:
IMG-20160512-WA0006.jpg
IMG-20160512-WA0003.jpg
IMG-20160512-WA0004.jpg

I am posting some pictures of the cured blocks. These samples developed cracks after 10-12 days and these seem to widen to some extent and then stop.
Please help. Urgently.

i have the same problem but with water curing not steam curing and i am searching for solution >>
can u help me??
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Re: CLC blocks with Fly ash only - urgent help required

Postby Alex » Mon Oct 24, 2016 9:21 am

Hello All!

We found out that among all of the reasons such a cracks could be foaming agent.

So, the typical way to resolve such a problem is:

1. try to increase water that you use for cement and sand mix
2. use covering for curing blocks, like here https://www.youtube.com/watch?v=_DwoQEN-yt8
on 6min 35sec
3. never keep blocks on the sun first 30 days
4. use as much sand is possible instead of cement - for example 280kg cement and 300 of sand, not 340 of cement...

Finally, if still having cracks
Foaming agent
1. use only protein based foam
2. good quality - GreenFroth and etc.

Unfortunately we have no dealers in India, but we hope someday we will find them :)

Good luck and if you have any problems write here, I come back from long trip and ready to help.
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Re: CLC blocks with Fly ash only - urgent help required

Postby dogragurjeet » Thu Nov 03, 2016 2:59 pm

Hi Alex,
Returning to this forum after a long time, and thank you for your reply. The problem we faced was eradicated with the use of fly ash from a different source and also changing to a protein based foaming agent. We had to increase our cement content in the mixture slightly, but the results are worth it now.
The only problem we face is that the blocks are exhibiting high water absorption, to the tune of 16-18%. We have not been able to control this parameter. Also sometimes there is appearance of honey comb holes (individual large ones, spaced apart and not interconnected) on the surface, but that I guess is due to the improper cleaning of the moulds and the excess application of the mould release agent.
We were previously using Calcium chloride to reduce the initial setting time of the concrete mix, but then after certain experiments found out that it was not helping much so removed it from the mixture all together. Could this be increasing the water absorption, because previously we used to get a value of approximately 14%. I do not see any scientific reason to believe the same, so though of asking you for help again.
Attachments
IMG_20161017_124218.jpg
Our foam concrete blocks storage in factory
IMG_20160926_100901.jpg
Our foam concrete blocks storage in factory
IMG-20160921-WA0016.jpg
Our foam concrete blocks in action for a residential project in Jamshedpur, India
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Our foam concrete blocks in action for a residential project in Jamshedpur, India
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Re: CLC blocks with Fly ash only - urgent help required

Postby ammuchennai » Fri Nov 18, 2016 8:08 pm

The Crack arise following reason,
-Accelerate very early or accelater chemical percentage high,
- Water usage higher,
-Calcium content more in Cement or Flyash
- Atmosphere Temperature high when procure porduction
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Re: CLC blocks with Fly ash only - urgent help required

Postby Alex » Fri Dec 02, 2016 7:43 am

dogragurjeet wrote:Hi Alex,
We were previously using Calcium chloride to reduce the initial setting time of the concrete mix, but then after certain experiments found out that it was not helping much so removed it from the mixture all together.

Absolutely correct decision.

Could this be increasing the water absorption, because previously we used to get a value of approximately 14%. I do not see any scientific reason to believe the same, so though of asking you for help again.

Fly ash can have different components. It depends on the way of catching ash on electricity station and coal itself. If is used "dry" method (the most of stations) then fresh fly ash has some active components that could destroy foam structure.
So try to get "old" fly ash maybe 1 year old.

Also foaiming agent could be the reason. If you want to be sure just try to produce 2-3 cubs with old foaming agent. (I recommend to do it)
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Re: CLC blocks with Fly ash only - urgent help required

Postby NanoCon » Thu Nov 23, 2017 9:31 am

Hi Alex,

I am from Nepal. We are manufacturing CLC blocks, brought machines from India. Initially we produced clc blocks of 800-850 density with 80% fly ash and 20% sand then we noticed that tremendous cracks on block surface as well as masonry wall surface. So we decided to increse the density to 1000 kg/m3 with mix proportion of 250 kg cement, 650 kgs of sand, 450 of fly ash, water 175-200 lits. we are using protien based foaming agent with 1:30 ratio. With this product, our clients are facing wall surface cracking by using clc bricks.

Would you please suggest us exact solution for suck cracks problem. Is this only of our problem or, most of clc masonry faces same problem.


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Re: CLC blocks with Fly ash only - urgent help required

Postby Alex » Thu Nov 23, 2017 10:11 am

Hi Roshan,

the problem could be in fly ash - it has very different components, depends on region and electricity station.

Also when you use fly ash you have to add more water, maybe add fibre - http://www.ibeton.ru/pic/fibra.jpg

Also blocks must stay in wet condition 28 days, before you can use them for mansory.
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Re: CLC blocks with Fly ash only - urgent help required

Postby NanoCon » Thu Nov 23, 2017 10:40 am

Thank you Alex for your prompt reply.

Do you have any agency near by us to get new foam generator. My current Foam generator is not supplying constant density of foam too. Once we set on correct density i.e. 80-60 gm/lts. it automatically changes to more liquid or air. Is it possible to buy new foam Generator from you? How much would be the price.

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Re: CLC blocks with Fly ash only - urgent help required

Postby Alex » Fri Nov 24, 2017 7:00 am

Hi,

no, we don't have any agencies and usually deliver only complete plants for foam concrete.

In your case I can recommend try to fix the problem with foam generator that you have. Usually simple cleaning can help to fix such problem.

Buy the strongest and cheapest eatable vinegar. Make 10 liters solution about 10% of vinegar and 90% water.

1. Start foam generator without air just with water 50 liters and after that with air and water 50 liters.
2. Start foam generator without air with vinegar solution until it almost suck all solution. Stop.
3. Wait for 2-3 hours.
4. Start foam generator without air just with water 50 liters and after that with air and water 50 liters.

It will clean the inner part and maybe fix problem.
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Re: CLC blocks with Fly ash only - urgent help required

Postby NanoCon » Fri Dec 08, 2017 9:11 am

Thank you Alex,
I will follow your advice soon. Currently my CLC bricks are showing shrinkages more resulting as shown in picture. Do you think it’s only due to Foaming agent or water-cement ratio on my mix?
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922058C9-E939-4340-9320-1C5C62629BD9.jpeg
922058C9-E939-4340-9320-1C5C62629BD9.jpeg
922058C9-E939-4340-9320-1C5C62629BD9.jpeg
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D10380E8-8E36-4EED-9128-5E9AB44C7C29.jpeg
9DB9ED09-C581-4840-B8EC-2B372137A2B8.jpeg
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Re: CLC blocks with Fly ash only - urgent help required

Postby Alex » Fri Dec 08, 2017 9:44 am

Hello,

I can see, that maybe (not for sure), the reasons is in foundation micro movement. In this case regular bricks also could give such cracks. Look attached picture.

In any case blocks should stay wet 28days after production and only after that period you can use them for construction.
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2017-12-08_114049.jpg
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