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A typical mortar mix ratio is 1 cement : 3 sand. But what is the water ratio? Is it 0.5:1:3?

Would a 0.5:1:2 ratio be a stronger mortar?

Our next door neighbor has a dog that digs like a pro. The dog somehow manages to dig underneath some parts of our wire fence netting and get through. So I have thought of filling the holes with mortar.

I previously tried to fill the holes with concrete made with 0.5 water : 1 cement : 2 sand : 3 gravel, but the mix I made easily crumbled apart. Could that be because I bought gravel made of 0.5inch stones?

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  • Your mix was too dry It's hard to add to much water but being to dry it will crumble
    – user31779
    Jan 17, 2015 at 8:46
  • It also takes several days to harden and probably 2 weeks to cure. You'll need something (wooden stakes, etc) to keep the dog and others from disturbing the mixture until it has hardened. For this situation I would recommend sand, and gravel. Maybe try some quikcrete with stakes, or wooden boards to prevent the disturbance for a couple weeks, until full curing.
    – user43434
    Sep 12, 2015 at 15:32
  • I've only today been reading up on these things and saw that if you add a very small amount of plasticizer, it will release water that is trapped inside cement micro-clumps and as a result, despite the water being in very low amount, the whole mixture will start to flow and be a lot more viscous and workable. So it seems to me that using just cement and sand and gravel may not be enough, unless you plan to use a lot more water but that excess water will have to evaporate and the whole thing will shrink or crack a lot more. I suppose for your application outdoors, this may not be a big concern.
    – Daniel Katz
    Feb 20, 2021 at 20:33

7 Answers 7

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The less water the better, to a point. Excess water will weaken the mix. At some point in the other direction, there is not enough water for the hydration process(around 0.25:1 water:cement). In general though, to have a workable mix, there will be enough water for hydration. Use as little water as possible to make a workable mix, around 0.45:1 is fine. Don't use mortar for bulk fill, it's a waste of cement. The gravel in concrete is just filler, saving cement.

The concrete you mixed is sort of the standard DIY ratio, I don't know why it didn't work. While 0.5" gravel is a bit small, it can't be the reason for crumbling. Perhaps the cement was old? It may have absorbed enough humidity to partially hydrate, but not so much that it bound together.

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  • In volume or weight?
    – mateos
    Oct 12, 2017 at 19:37
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It is virtually impossible to specify the proportion of water in a concrete mix due to the wide range of moisture content in the sand used, Regarding "old" cement powder - if kept completely and utterly dry it will work fine after literally years. The only downside of using old cement is that the Chromium additives change from relatively harmless to relatively harmful. In my opinion if proper precautions are taken (e.g. respiratory and skin protection) this should not be a problem. Best mix to fill up these holes would be 1:4 ratio by volume cement to sand/ballast mix (20mm stones in the ballast). The total volume of cement in each hole must be at least 1 litre.

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  • Dry mix ratios can be played with. A slump test tells you to add more or less water.
    – Mazura
    Apr 17, 2015 at 1:10
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The correct mixing ratio would be 1:1.5:1 — 1 cement : 1.5 sand : 1 gravel stones with 0.4 water. If you use more water it will leave holes (porosity of the mortar), and if you use less water, it will not lead to hydration.

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You're talking about concrete, not mortar. Mortar is used to stick things together, not stand alone. A ratio by weight of 0.5 water, 1 cement, 3 sand, and 3 gravel should make a fine concrete, although a little less water (0.4 by weight) would make stronger concrete. The same by volume ( ie. buckets) is a good ratio as well, 1/2 to 1 to 3 to 3 (or a little less water- too much water weakens the concrete, and there will always be some water content in the sand). Make sure you have Portland Cement, not mortar mix or some other pre-mixed product. Adding your ratios to a pre-mix would greatly reduce the cement content, resulting in a disaster such as you described. For a stronger mix, increase the cement a bit, and reduce the sand.

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Not exactly sure why your original mix failed but yes, you're trying to make concrete, (mortar is a no gravel finer mix for laying brick, block and stone, plus rendering finishes etc. in layers usually no more than 1/2" or 13mm thick)

It's possible that it was too thin? On a really solid base you might just get away with 2" (50mm) but really 3" (75mm) is a 'minimum', with 4" (100mm) being the 'norm'.

Right then concrete. A 'standard' mix if there is such a thing, is 1:2:4 which is one cement, 2 sharp/washed sand and 4 gravel/crushed stone. This is fine for general concreting jobs like pathways, floor slabs etc. often in thicknesses from around 3" up to 6" (75mm to 150mm).

Thicker concrete for things like foundations and larger mass concrete is usually a 'weaker' mix of 1:3:6 which is one cement, 3 sharp/washed sand and 6 gravel/crushed stone.

In all concrete just enough water should be added until the mix folds nicely off the paddles/tines inside the mixer. If the paddles run straight through the mix it's too wet, if it crumbles it's borderline too dry. Dry concrete will dry very strong but it needs careful placing and compacting/agitating to get rid of any air in the mix. Technically as someone else said earlier, there only needs to be enough water in the mix to hydrate all the cement particles but in practice bung enough in until you get a nice workable product that doesn't slop but doesn't heap up in crumbly piles either.

These two mixes cover the vast majority of concreting works in domestic construction (in the UK at least).

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Mortar mix:1/2 of a 94lb bag portland cement 1/4 of a 50lb bag type S lime 14 shovels Masonry sand Aprox. 3 to 4 gallons water this depends on the thickness that you prefer for the application.

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The half inch stones aren't the problem.

It was supposed to be 1:1 1/2:1.

  • 1 cement
  • 1-1/2 sand
  • 1 gravel

The concrete needs water - not too much - but should be a moderate amount for it to make the cement react rapidly.

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