The Case of The Missing Concrete
When I began making up my Concrete mix, I used a Cement:Aggregate ratio of 1:3 by VOLUME, then added enough water to make the mixture as runny as I wanted. For example, I used 4L cement and 12L of sand, and 4.2L of water. Which I assumed would give me 4+12+4.2=18.2L of concrete.
Big mistake!
The finished test panel seemed quite thin, so I measured the ACTUAL volume of mix that I had made up. To my surprise I found that I had only 12L of concrete!? I had lost 6.2L of Concrete! Then I had a think...(never a good thing)
Between the Cement and Aggregate (and to a tiny extent the Water) particles there are air gaps. When you mix them together, the particles fill these gaps.
And so that is why the concrete seemed to be disappearing.
So the ACTUAL volume of concrete produced was about 1/3 LESS than the CALCULATED volume of ingredients put into the mix.
So as long as this pattern is the same every time I mix the concrete (which is pretty likely as long as I use the same cement:aggregate:water ratio and the same type of aggregate). Then all I need to do is increase the volume of ingredients by 1/3.
Crisis over! Hurrah! :-)
Big mistake!
The finished test panel seemed quite thin, so I measured the ACTUAL volume of mix that I had made up. To my surprise I found that I had only 12L of concrete!? I had lost 6.2L of Concrete! Then I had a think...(never a good thing)
Between the Cement and Aggregate (and to a tiny extent the Water) particles there are air gaps. When you mix them together, the particles fill these gaps.
And so that is why the concrete seemed to be disappearing.
So the ACTUAL volume of concrete produced was about 1/3 LESS than the CALCULATED volume of ingredients put into the mix.
So as long as this pattern is the same every time I mix the concrete (which is pretty likely as long as I use the same cement:aggregate:water ratio and the same type of aggregate). Then all I need to do is increase the volume of ingredients by 1/3.
Crisis over! Hurrah! :-)
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4 comments:
Sometimes I wake up in the middle of the night and think to myself: 'thank god I'm not an engineer'.
Then I go back to sleep. =)
Why not measure it by weight instead?
Well it was because I had no weighing scales, but I've managed to get hold of a set now. :-)
Hi Garreth, This is Johan Coetsee in Mozambique. I see you are making progress. Contact me on lamontibane@tdm.co.mz. I would like to get some details from you about the progress you are making on panels. how is the strength now?
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