Mortar and Concrete - excess cement

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.

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

Bill Wright explained on 26/06/2017 :

Which is why engineers do a slump test on newly delivered ready mix, before accepting it.

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

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?

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

I used to do that when I was a chain boy.....and make cubes ........

Not just engineers. Readymix customers. Me.

Bill

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.

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.