Salty Water for Curing Fly Ash Cement Bricks
by Anant Karnani
(Jodhpur, Rajasthan, India)
Q: Dear Alan,
1. I had gone through your answer to one of the posts regarding admixtures for fly ash brick curing time.
You mentioned about CaCl2 as a good accelerator, and at the same time having corrosive nature.
In continuation to the same query, i use a typical mixer to mix my raw materials i.e. crusher dust, grit(3-6mm) and cement, what impact will CaCl2 have on my mixer?..How can i protect it?
Since we are not directly using the concrete for masonry purpose( as we are manufacturing bricks & blocks), is there any other admixture that you suggest?
2. Another query i have is that we use cement ranging from 7-10% in our mix. And in our region cement is a little expensive and we would like to reduce the quantity of cement in our mix but at the same time achieve the optimum strength (100-150kg/cm2).
Please suggest some admixture for this application
3. The final query i have is that of using salty water in the mixing and curing of bricks/blocks.
What is the effect of salty water over the properties of concrete blocks?
Await your reply eagerly...
With Warm Regards,
I will touch on your questions for fly ash cement bricks here and see if I can cover all of your questions.
To begin with, you have asked what effect CaCl2
will have on concrete. There is some speculation that it can counteract some of the aggregates that are placed inside of a mixture that contains magnesium
However, other studies have shown the only effect is has on the bricks is an improved amount of curing time. I would say there is little concern for actually protecting your mixture from the CaCl2 that you place in it. Another choice you have, as you know, is salty water
Since concrete can be rather expensive, you might want to consider adding in some gypsum
. This slows down the curing time, which can be offset by the CaCl2, but still helps you to maintain the bond that you are looking for.
The strength of the final product can vary slightly in the process and using actual concrete will be very important whenever you can find it financially feasible for the creation of your bricks.
I will let you know that your cement in this mixture needs to be between 5 - 10% to help ensure that your bricks retain their strength.
If you choose to go down in this process to the lower end, pay close attention to what you are adding to replace it so you can ensure that the overall strength is retained.
Typically, salty water in bricks is used to help speed up the curing process. Normally, you will find that it does offer some negative results though in the creating concrete even while it is curing faster.
To begin with, your bricks can be up to 20% weaker than if you used standard water alone. Along with that, it has a corrosive nature and if you are putting rebar inside of your bricks, it will break them down in this process as well.
It is because of this that you want to be careful with how you end up constructing the fly ash. This includes the actual construction of the bricks as well.
There are several ideals that people use in terms of the formulation of their bricks.
It is important that you focus on delivering quality with these bricks as an improper formulation can result in unusable brick, which becomes more expensive than adding in the proper ratio of ingredients, as you know.
Hopefully, my responses have provided you with some of the information that you are looking for.
If it were me, I would keep the CaCl2 in the concrete, consider adding gypsum to the mix and avoid the use of the alternative water. This will continue to help you create the best fly ash cement bricks and you should be able to continue to produce them with no trouble at all.
I wish you all the best in crafting your fly ash bricks and I hope that my answer has helped you out in this process.
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All the best,
AlanMeet-Mr-Concrete.comSubscribe to MMC RSS FeedFind Top Notch Local Concrete Pros for FreeMeet-Mr-Concrete.com provides concrete construction advice at no charge and in good faith for consideration only. We do not warrant the implementation of its content and are to be held harmless when and if any advice or ideas provided are utilized. The risk from using it lies entirely with the user.
Re: Salty Water for Curing Fly Ash Cement Bricks
by Anant Karnani
(Jodhpur, Rajasthan, India)
Q: Dear Alan,
Thanks for your reply to my query.
Sorry, I could not find a reply option on your answer page, hence i am writing back with a follow-up post.
I have few more fly ash brick queries :
1. In one of your replies to some post you had suggested using 3% CaCl2 for accelerating the process.
Now i want to know what are the properties required in the CaCl2 for using in manufacture of fly ash cement bricks?
By properties i mean purity of CaCl2. Because as you know more the purity of CaCl2 the more costly it will be.
2. Along with gypsum can i use lime CaO, for replacing cement?
If yes, then in what proportion?
Also, what %age of Lime?
Can we also use hydrated lime Ca(OH)2 instead of lime ?
As eventually when we mix the raw materials in the mixture, lime automatically reacts with water to form calcium hydroxide.
If yes, then in what proportion?
Also, what %age of hydrated lime?
3. In your reply you have asked to avoid using salty water, right?
But can we use the salty water for curing the bricks?
In our region, only salty water is available.
If we have to cure the bricks with sweet/normal water, then our brick will not be economical.
Hope to receive your response soon.
Thanks & Regards,
A: Hello Anant,
Thanks for your reply on your salty water questions. I'm writing you back as soon as I could... I've been swamped with projects and my studies. I am going to merge this response with your previous query.
I'll see if I can help you to better understand the information that I have for you. Your questions are a bit technical, but I think I should be able to help you with this process.
When you are using the 3% mixture of CaCl2 to help accelerate the curing of fly ash cement bricks that you are making, you will want a minimum of 72% pure CaCl2 in the mixture. If possible, you will want to get closer to 82% as this will help matters. But there certainly is no need to have it go beyond this point.
As you mentioned, it does get a bit more costly the higher the level of purity your mixture is.
A portion of CaO can be used to replace cement. But what you need to realize is that it does affect the integrity of the final product.
I would say you could replace up to 33% of it with Lime. This means you keep it at a 1:3 ratio, if possible I would stay lower than that, but I understand you are looking to cut costs.
Most builders will discourage you from using Ca(OH)2. While being less expensive, it would not be a good choice for you to do.
As there are other options for fly ash cement bricks, this certainly is not one of the better choices.
As I mentioned with the salty water, you will experience weaker bricks and it will corrode any rebar that you might be using with the concrete.
Due to that, I would suggest you not use it.
However, I cannot tell you what to do. If you choose to proceed with the use of this form of water, then it is completely up to you.
Now, Anant, I know I might not have told you what you wanted to hear, but I believe it is important to be honest with you.
What you do in the end is going to be completely up to you.
You might find that using any or all of these items works for you and it is effective for your needs.
But, if you are using any of this material in the construction of homes or structures, I do urge you to consider the safety of the individuals that enter the area.
Inferior bricks can cause structural issues. This is something to keep in mind when you are going over the costs of production.
Sometimes the things that increase the price slightly will make the difference.
In addition to that, when your product becomes known for being higher quality, more people will look at your product and take into consideration that value that they get for the price.
I hope this has helped to answer the questions you had Thank you for continuing to visit my site. I am working very hard to make it a diverse and dynamic concrete resource.
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