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I need white concrete for a countertop sample, but the only white concrete-like product is white mortar. If I just add an equal sized bag of gravel to the mortar, will it be close enough to use as concrete? If not, what else do I need to add, and at what proportions?

  • You can't find "white portland cement" anywhere? Mortar typically has sand and will not give a smooth surface. – JPhi1618 Dec 17 '15 at 22:41
  • @JPhi1618, mortar can be finished smooth with techniques similar to making concrete smooth; tamp and smooth with metal trowel to bring water up to the surface, giving a final smooth trowel job with metal float. – Jimmy Fix-it Dec 18 '15 at 20:40
  • What type of mortar? Type S? Thinset? – Joel Keene Dec 20 '15 at 5:24
  • It looks like the available white mortars are thinset. I did end up special ordering white portland cement to make the concrete thanks to all these comments and responses. – jgrant Dec 21 '15 at 17:51
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Mortar is similar to concrete in that they both contain Portland cement and sand. The 2 different ingredients are that mortar has hydrated lime and concrete has larger aggregates (stones). Using mortar in place of concrete isn't a good idea as the two have dissimilar compressive strengths. If you are only able to use the white mortar you may be able to make it concrete-like by adding a shovel full of Portland cement and than mix (1) shovel of gravel with (2) shovels of plaster sand and (1) shovel of mortar. The added Portland cement and sand may produce a strong enough mix, but the mortars' hydrated lime is the weak link. As been commented on, it may be easier to seek-out a pre-mixed white cement if possible and use dye for a brighter color. Look for concrete dye at your local building supply store. They should have several colors available including white. A pint is the typical liquid amount. Depending on the shade of white you desire (brilliant down to greyish white) you may need several pints. You will have to experiment with proportions to get the right shade of white, but as was pointed out in comments you may be using more dye than is cost effective if you want a "white" white.

  • Back in the day, to make cement, the proportions were 1 shovel portland cement, 2 shovels sand and 3 shovels washed gravel. If I remember right masonry cement (mortar) is different by not just the lack of gravel, but it has limestone added to it too. It would be difficult to "unmake it" concrete. – Jack Dec 18 '15 at 8:18
  • Have you used the white "dye" with grey concrete? I'd be surprised if you could get anything lighter than "greyish white", but my only experience is mixing paint... – JPhi1618 Dec 18 '15 at 14:30
  • Thank-you both for your comments. I have edited my answer to reflect your suggestions. – ojait Dec 18 '15 at 16:46
  • Not all mortars are the same as concrete! – DA01 Dec 18 '15 at 19:56

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