Matching stucco/parging mix and color

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Old 07-08-13, 07:21 PM
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Matching stucco/parging mix and color

Recently did some work installing a new basement window and chipping out old cracked up masonry outside of the window as the photos show. I am trying to figure out the correct mix to use for repair to this section. I have tried a regular stone mason mortar with quickcrete sand added but this turned out far to grey. My next thought was to try a layer of mortar + sand probably 1/4 to 1/2 inch and then top with a Portland + sand + lime + color -coat probably 1/4"? I'm not sure if I'm on the right track but I'm looking for some suggestions!
 
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Old 07-09-13, 02:40 PM
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Matching stucco color is a knack. Maybe there is a masonry supplier in the area that sells finish stucco. Take a piece that you want to match and buy a bag of the material that is closest in color. If you must adjust the color a little you can buy some mortar color to darken it or add some of a different shade. If it is of about the right intensity of color but is too yellow for instance and needs some brown get some brown color to add to it. Problem is you don't know what color you have until it is set and dry.
If you want to try your own color use masonry cement, no additional lime and mix it 2 parts cement : 5 parts sand by volume and add the color. It is actually best to dry mix all the ingredients then add the water and mix. Hold out a little of the dry mix to mix with more color if needed to add to the mix.
It might be easier to do this in natural cement then paint it all.
 
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Old 07-09-13, 06:43 PM
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thanks Tightcoat. Do you think I should be considering a lime based mixture rather than a Portland based? My home was built in 1930 which I think was about the time Portland was starting to take over. The house is block foundation though so maybe Portland would be fine? I was experimenting with a 1:2:6 (white)Portland,lime,sand combination. I can get the color close but just concerned about longevity and harsh weather here in MN so want to get the correct mix. Some have also told me to stay away from bonding agent as that will not let the house "breath."
 
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Old 07-10-13, 09:28 AM
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Use a Portland cement product. Masonry cement is Portland with other stuff in it and is more durable than lime, If you don't use a bonding agent make sure you get the existing surface really clean. Get down to some raw concrete, On a spot that small some bonding agent is not going to make a serious difference in the breatheability of the house.
White Portland will take a lot more color to give you the same color that you have. White tends more toward pastels where masonry will give it more of the grey shade like you have now.

Something you can do is patch it and see how close the color comes. If you need to adjust it after it is set and dry you can mix some mortar color and neat cement, either Portland or masonry with water to a thin paintable consistency, thinner than most paint and paint it with that. It will dry quickly and you can see if the color is right. If not you can add more color or more cement and water until you get it right. Even if it takes several tries you can get it all in one day.
 
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Old 07-18-13, 01:00 PM
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Thanks again for the suggestions Tightcoat. I've done a couple tests and getting ready to apply this weekend. One other question: it seems that I can more closely match the existing color/texture if I use muriatic acid (10:1 water -acid) on the new parging mix (after 24hrs cure time or so). Seems to help bring out the aggregate. OK to use muriatic? If so how long would you recommend I wait to apply the acid?
 
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Old 07-18-13, 03:17 PM
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I don't like the idea of using acid. Try floating the new work with a sponge float either a red one or a green one once the material is tight but not set. That should bring out the aggregate and you won't damage the work by putting acid on it.

Wet the float before you use it and it's alright to wet either the wall or the float again if it drags too much or if the work is too tight to pull out the sand. This is also the way to blend the surface of the new with the old. Press harder on the old work and not so hard on the new work in order not to dig the new work out and not leave it flush.
 
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Old 07-18-13, 04:07 PM
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I used a wet red sponge float and then wet sponge once the material had set. Seemed to still drag the mix over the sand aggregate. Perhaps I used too much of a sweeping motion rather than just blotting. I'll try another test tonight with more of a straight-on motion and also being sure to rinse the sponge float and sponge regularly. You think using something like vinegar instead of acid would still be too hard on the mix?
 
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