Aggregate Moisture Corrections Pt2 - Example (with Excel Sheet)
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- Опубликовано: 5 окт 2024
- An example is presented on how to do an aggregate moisture correction for a concrete mixture. www.tylerley.com
The form used in the example and a spreadsheet can be found here:
www.dropbox.co...
Hi Tyler, Many thanks for pointing me in the right direction for aggregate moisture values. As always, your videos give an informative insight to concrete science. Just to make things a little easier for Concrete Connoisseur's, most modern digital scales have a facility called "Tare" which works the same way as a weighbridge for trucks. Place your bowl on the scale and zero the scale by pressing the Tare button. It automatically tares the weight into the scale so it only weighs the content of the bowl. I use a large shallow baking tray for baking fines so its faster and more efficient, always remember to check and stir the aggregate regularly and to let steam out of your oven.
At the moment I am designing a new type of concrete with specific properties that will appeal to different markets. All of my aggregates are what I call Dry Weight Aggregates (DWA's) or one could call them NSSD (100% dry) aggregates. I buy them dry so I have complete moisture control over my mix.
So I basically take a1kg sample of my aggregates as a standard purchase and then oven bake them. The test results figure came to 9.56% moisture content in the aggregate. So I then add this 9,56% of water into my premixed viscosity modifier (of my own making) plus the water for the cement and rinsed the aggregate well before adding the cement for which I calculated my optimum WCR (In this video Tyler's is 42%) and then added it to the mix followed by a super plasticizer.
This system of mine (Basic as it is) has proved to work without any losses to the quality of the mix. So in the UK with bagged aggregates (not loose bulk) I am working on a 9.5% standard moisture content from the same supplier that is. Aggregate shape in my opinion is very important because it can affect concrete quality, increase cracking risks and of course carry more water into the mix.
Concrete is confounding, complicated and a completely brilliant material.
Jon - That is great that you can get your aggregates dry. That is not usually an option in the places where I work. I agree with your tare comment but there may be several days between weighing the wet sample and the dry one if you use an oven and so it is best to write it down. Also, we find bowls and containers have different weights and this can make a difference in your calculations.
I talk a lot about aggregate shape and mixture design in a few different videos. You may want to check out the Tarantula Curve playlist for some detailed discussion and more tools. You can get it here: ruclips.net/video/V-r4-9OcuyY/видео.html
Good luck on your new product. Sounds like you are headed down a cool path. 9.5% absorption is very high.
Oh yeah - general concrete stuff can be found in this playlist. It puts a lot of it in one place! ruclips.net/video/HRVIoWFltw8/видео.html
Thank you!!!
Thanks for the easy and professional lecture
Thank you!
thank you !! Realy helped me !!
Awesome!!! I am glad you liked it.
Hi Tyler, many thanks for your profesional way of teaching, I could be that I have experianced this effect when load our mixer by volume & discharging the mix in less than 15min, could be that the limestone aggregate didnot absorb mix water through that period of time. Therefore mix strengh comes out better.
Great video series. You probably know but you made a transcription error from equation 3 to your chart of .993 to .933
Thanks!
Thank you very much you covered the subject in very professional way, yet i have couple questions
1. By changing the the weights ( replacing aggregates by water & vise versa ). Are we still maintaining the original batch volume?
2. We added 29 lb of aggregate 2 , still these 29lbs contribute with 1.023 moisture content. Should we consider the moisture content & absorption in this new weight once again ?
Thank you again
Thank you for these videos, they are very helpful!
We are working on starting this in our facility. During the soaking and drying process to acquire the SSD weight of our aggregate, the weight dropped by 5g even with fully saturated rocks (the rocks soaked for 27hrs). Could it be that the water washes some of the fine dust away? In our daily sieve analysis results there are usually around 5g of dust in the pan at the bottom of the sieve stack.
We are using 10mm (3/8") aggregate, if that helps.
How do we account for this in our calculations? Thanks!
Hi Tyler, this is great, and thank you for this video!
One question - Initially, you have the mixture proportions at SSD. Does that mean you have already accounted the moisture corrections after designing the concrete for a required strength according to a guideline (for e.g., ACI 211.1)? The point is, when you follow ACI 211.1 you will first evaluate the dry batch weights, and then do the water adjustments to get the SSD batch weights. But still needs to do corrections for the aggregates, am I right?. An explanation would be greatly appreciated talking about the main steps after getting the dry batch weights.
I just add water until it's almost watery so I can easily apply it wherever I need.
If I put too much water, I just leave it on sun to dry before I put bricks on. I've built 50+ houses that way.
Yo Tyler, may I ask what's the difference between SSD and moisture content though.
What if i use oven dried aggregates on my sample, will i use just the water calculated or should i add the absorption of the aggregates? (No moisture content)
Does aggregate moisture have any effect on curing?
If so, are you any better off with water saturated aggregates at the plant? Or will the rock(limestone in my case) suck up enough water in the mixer on the way to the job that it really doesn’t matter?
Let’s just say that from the time the materials get put into the truck at the plant, to the the time it hits the ground on the job site is 20-30min.
Richard,
I don't think it matters for normal aggregate. If you have light weight aggregate and they are properly saturated then these might be able to help. We are about to start to study this in our lab.
Hi All, Tyler, nice job, this causes so many problems... talk to me about the costs of not doing correctly or at all..., it’s incredible... get in touch.... please. Jason, MD, Hydronix Ltd. Well done....
You do all this and the contractor's guys say "??? its concrete not rocket fuel!" and proceed to weigh it all as SSD and pencil whip the batching invoice/records. --real world. [unfortunately those who understand the engineering are vastly outnumbered by those who only think they understand and you can't babysit every step of every process]
(If it happens regularly with loading air cargo under the FAA do you think it won't happen with concrete batching?)
Hello Tyler - I am a Concrete Quality Control Manager in the Indianapolis area, I have developed my own spreadsheets for many applications, but I always like to look at others for ideas on improvements. Can you send me this spreadsheet?
I think it is in the description of the video.