Mortar and Concrete - excess cement

When mixing mortar or concrete is there any reason not to use more cement than necessary? If I use a standard mix I will end up with surplus cement which won't keep. If I use more cement, I might be able to avoid buying one bag of sand. Not a major saving, but there is also the problem of getting rid of the surplus cement.
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Michael Chare

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On 26/06/17 15:58, Michael Chare wrote:

If you go "stronger" than 3:1 sand/cement, it can start to become less strong. If you remain weaker than 3:1 usually no problems barring a few special cases.
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On 26/06/2017 15:58, Michael Chare wrote:

Since the cement binds the sand gains together I should think that a serious excess of cement would mean there was cement not in contact with sand or ballast. That would presumably result in a weaker concrete.
Cement that gets damp sets to form a not very strong substance.
Incidentally the worst thing you can do use too much water. The stiffer the mix the stronger the concrete.
Bill
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Bill Wright explained on 26/06/2017 :

Which is why engineers do a slump test on newly delivered ready mix, before accepting it.
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On 26/06/2017 16:58, Harry Bloomfield wrote:

I have found it surprising how much difference only a little extra water makes.
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Michael Chare

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I used to do that when I was a chain boy.....and make cubes ........
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On 26/06/2017 16:58, Harry Bloomfield wrote:

Not just engineers. Readymix customers. Me.
Bill
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On 26/06/2017 16:32, Bill Wright wrote:

However once it is past initial set (Green) the more water it gets the sooner it will attain maximum strength ... it is not as many think by drying.
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On Monday, 26 June 2017 15:58:40 UTC+1, Michael Chare wrote:

The only reason not to is cost, until you reach somewhere around 3:1. Going richer than 2:1 or 3:1 reduces strength.
NT
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Michael Chare wrote:

Three years ago I used a small part of a bag of cement to point between the drive and the walls of my house. I stuffed a black plastic bin liner in to the bag of cement and stored it in the garage on top of a bin liner. A couple of weeks ago a small part of the pointing fell out when I jet washed the drive............... like this sort of pointing tends to do. The cement in the bag was still powder, no lumps and when mixed with sand/water cured very well. Food for thought?
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As has been pointed out, a standard mix isn't called a standard mix for nothing.
As you say cement won't keep whereas sand will. One way to avoid waste in individual jobs which won't take a whole bag, is to have a job or jobs on the side that can use up any surplus mix but don't necessarily need to be finished off in the one go. Having the small job(s) which need to be finished off at some point can also act as an incentive to get started on the next big job.
michael adams
...
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On 26/06/2017 15:58, Michael Chare wrote:

I would not use over rich mix .... these mixes have been tested and confirmed over years ........ too much cement will end up with brittle concrete.
With mortar it is also designed to force a crack on mortar line in the event of stress not the brick or block.
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