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Heading: 1.1.4Aggregate Fines
Incorporation of aggregate crusher fines in concrete seems to us like a green practice because using a material that might otherwise become waste is good for the environment; however, we understand that this idea may not earn green points or that no one has tried to earn points before. Does anyone have experience with this issue or know where to find more information please ?

Margaret Reed

Lots of work has been done on this. Check out The problem is that the crusher fines have a higher water demand, which increases shrinkage and cracking and reduces strength. You may be able to use a cheap aggregate but the ultimate concrete cost will be much higher because of the need for additional cement.

I am having to do this in Zambia, where there is no good sand. We are using 742 lbs of cement/cyd to get an average strength of 7000 psi. And that is with using a lot of superplasticizer.

Jay Shilstone
Jay Shilstone

Good idea to use crusher fines and if it is done well, it will be the concrete producer who will get your green points since he has a chance to use less "cement".
I disagree that more fines means automatically more water (and consequently more cement). Initially it might but if you increase fines correctly, water demand can well decrease. It all depends on the particle size distribution of ALL the fines (lets say under 125 µ). New milling techniques of cement has increased the water demand due to steep curved PSD. This can be compensated by other attractive fines such as calcium carbonate fines (CCF) on the lower end of the cement and fly ash and fine sands on the upper end.
Have a special lab, cement or CCF producer look at ALL the fines, especially yours!

The introduction in the Netherlands of the French concrete culture to use more fines to increase performance has been a great success. It means reducing portland cement while increasing strength and lowering the carbon footprint. We have two big aggregate suppliers here with great success stories on this with many customers.
Jay, what is your definition of "cement"? Do you consider composite cements and/or seperate added SCM's also cement?
Boudewijn Piscaer
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