# Why does concrete cure white and portland cement cure grey?



## jgray152

This is something that has been bugging me and I think it may be due to the extra calcium in the redi-mixed concrete compared to the very little in portland cement??

Anyone know the reason? If I mix portland cement and sand together to get a grout mix which I use for my faux rock retainer walls, it will usually cure a dark grey or mild dark grey where as if I get it delivered from the concrete company it cures very white which is better for acid staining.


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## CJKarl

I have found it to vary from....Manufacturer of the cement, quarry that mined the sand and even how much water is added to the mix.


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## jgray152

hmmm. Well thats a bummer. I usually mix my home made concrete mix real dry for strength. Is it possible if using a lot of sand or maybe a lot of silica or another fine filler to allow the cement to maybe not be so dense or turn it white or at least a light grey? I have got portland / sand to turn white after 3-4 days of curing but that is not always the case, I guess I got lucky on that mix.


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## 6stringmason

CJKarl said:


> I have found it to vary from....Manufacturer of the cement, quarry that mined the sand and even how much water is added to the mix.


Same here.


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## user50444

slag mixes get really white. pretty much every redi-mix producer is either adding fly ash or slag, unless you tell them straight cement.


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## CaliDesigns

Your percentage of portland in concrete is a lot less than your slurry mix. That's why a lot of concrete guys add white portland to their slurry mix to wet face steps.


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## concretemasonry

Mortar color is highly influenced by the sand color, while ready-mix is not because of the difference in the cement content. The lightest mortar will be a traditional portland/lime mix that has more workability and long term healing from the weather.


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## naptown CR

jgray152 said:


> This is something that has been bugging me and I think it may be due to the extra calcium in the redi-mixed concrete compared to the very little in portland cement??
> 
> Anyone know the reason? If I mix portland cement and sand together to get a grout mix which I use for my faux rock retainer walls, it will usually cure a dark grey or mild dark grey where as if I get it delivered from the concrete company it cures very white which is better for acid staining.


Portland cement comes in two colors white and gray. next time by white portaland.


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## jgray152

I know it comes in gray or white in bags but thats why it didn't make sence that portland in redi-mixed concrete trucks cured white or very very light gray where as portland in backs mixed roughly the same way cured gray or dark gray.

Its just something I will have to keep in mind thats all. White Concrete here is about $22 a bag verses $9.80 a bag of standard portland.


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## harpomason

thanks for asking as i have pondered over this same thing. I like my work to be consistant through out the job. Its one reason i try to avoid using dye or powdered color. when i can't talk them out of using it. I will measure very carefully every mix.
The man who schooled me on this trade told me that he remembers when a bag of masonry cement cost him 75cents and portland was $1-$1.25 per bag.


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## jgray152

Bringing this thread back as I want to find or make something that can be lighter in color other than spending $22 a bag on white cement. Home Depot does not carry it anymore so the only place I know I can get it is an hour away instead of 25 minutes away.

Masonry Cement I have read has more lime in it? Lime I read can make the cement whiter? So is masonry cement lighter in color than gray portland cement

I will be using Perlite in my lightweight mixes for now on which is white so that would help as well. 

If I were to mix White cement and Grey Cement together...what proportions should I mix at? Anyone have experience with this?


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## Tscarborough

In my area it is, but only by a tiny amount. You can buy titanium dioxide to lighten it if you want, but it is not cheap either, about 10 bucks per bag of portland used.


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## 6stringmason

Save yourself the headache and go get the white portland. Then charge more for your products containing the white portland.


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## superseal

White is what your looking for - buck up or cut it 50/50 25/75 if you a cheap azz


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## masonlifer

I've been using a mix with white portland to patch precast. Most of the time suppliers in this area don't keep it in stock unless someone places a large order. It's too expensive to sit in a warehouse waiting for someone to use it a bag or two at a time, and if not used soon enough it gets hard.
One source I have found is the local pool supplier. They keep some in stock for repairs on pools.


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## Tscarborough

Funny how very different areas are. We go through a couple of trucks a week of white portland and masonry, and we are slow. Plus our gray portland/masonry is very light.


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## jgray152

> Funny how very different areas are. We go through a couple of trucks a week of white portland and masonry, and we are slow. Plus our gray portland/masonry is very light.


Its aggravating... I think I'll start ordering portland from china, probably cheaper and lighter!

What brand of portland do you use Tscar?


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## Tscarborough

Lehigh, but I have sold imported white from Turkey. Not reliable enough for our volume though.


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## stacker

i agree with six.bite the bullet and buy the white.when i manufactured stone,and when we had an order for white stone,thats all we used.white portland and haydite.altho my dad did experiment with puting a gallon of white paint in with regular portland once.i didnt work:whistling.


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## Tscarborough

If he had used just the pigment KX, Titanium Dioxide, that made the paint white it would have worked but he would not have saved any money.


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## duburban

I deal with this all the time with my artisan concrete work. I can create white white by using white portland, white pigment, and marble/ glass aggs. For cost your going to have to at least be into it at the portland level. Not knowing what shade your looking for i can't really tell you how to mix. You can figure that out but factor in the cost of pigment vs the cost of portland. You may be able to add enough white pigment to the gray portland, you'll have to run the numbers and make the samples. We usually mix at around .2 cubic foot or so to create a sample that will actually transpose. Like others have said you can try changing your aggs too, but I'm tellin ya, once you add white pigment to white cement its white! 



jgray152 said:


> Bringing this thread back as I want to find or make something that can be lighter in color other than spending $22 a bag on white cement. Home Depot does not carry it anymore so the only place I know I can get it is an hour away instead of 25 minutes away.
> 
> Masonry Cement I have read has more lime in it? Lime I read can make the cement whiter? So is masonry cement lighter in color than gray portland cement
> 
> I will be using Perlite in my lightweight mixes for now on which is white so that would help as well.
> 
> If I were to mix White cement and Grey Cement together...what proportions should I mix at? Anyone have experience with this?


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## duburban

A note for choosing cements. Cheap clinker = Cheap cement = Cement that doesn't behave consistently and can ask for as much as .7% water to hydrate vs the .3% you want. 

My "rapid set" cement comes colored a lighter shade of gray, more towards white. It took acid stains great. You could easily get that shade by 1 gray 2 white. or 1 gray 3 white. 



jgray152 said:


> Its aggravating... I think I'll start ordering portland from china, probably cheaper and lighter!
> 
> What brand of portland do you use Tscar?


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## Tscarborough

You can not add enough white pigment to gray cement to get white, you can only get light gray. If you want white, you have to use white cement.


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## jgray152

It doesn't matter to me if its white or very light gray, as long as it doesn't cure .....medium/dark gray like it usually does


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## duburban

Tscarborough said:


> You can not add enough white pigment to gray cement to get white, you can only get light gray. If you want white, you have to use white cement.


 I was suggesting he mix the pigment with gray to see if gets a color he likes, not white.


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## Michael Olding

For vertical applications we use a high cement content stucco mix. It gives us much better consistency for texturing & staining purposes but I agree it can be a pain in the ass to get exact color matches. So much depends on application techniques, set time, humidity, cement manf, etc., etc.

It cracks me up when people say "... oh just match what's there." like it's no big deal... heh, heh, heh.

I wonder how far you could push this type of mix on a horizontal application particularly in a heavy freeze thaw settings? Seems that the sealer is the key to prevent moisture infiltration but I'm not quite sure yet.

I have a spray crete application down for 10 years in a rough environment that has done pretty well but again the key is the sealer.

I have a couple of test paving areas going through a rough winter this years with a 'lighter' homemade topping mix. We'll see what happens.


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## jgray152

Water infiltration is not really the issue....its when the water freezes and expands 5 times its size....thats when it becomes an issue. Air Entraining is a must in those applications..


Although, a cement topping overlay usually doesn't have air entraning...so yes the sealer is a big issue. I find the acrylics are the best for overlays. Penetrating sealers I find still let water in. Although most penetrating sealers breath so some of the moisture can leave but still

Matching concrete color is HARD! I have tried. sometimes going in one direction with the mixes which seems to make it lighter in color....will still produce a dark mix out of no where.

Does anyone know if Masonry Cement cures faster than Portland cement?


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## Tscarborough

Here is what I tell people that want to match mortar/concrete colors:

First off, you can't. Get over it, concrete and mortar can not be matched, because if you match it when the new stuff is fresh, it won't match as it ages.

Here is how to repair concrete and mortar and make it match:

Get somewhat close, then after it sets, rub dirt on the entire area and wash it off. Viola! perfect match, now and in the future.

Edit- No, Masonry cement and portland/lime mortars will cure at the same rate.


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## Michael Olding

I agree Tscar. People discount the huge benefits sometimes of plain ole' dirt!

You know for repairs (not toppings) I'll use an acrylic stain directly after the application to blend the color perfectly. When the repair material cures it blends in even better and I know what color I have before I leave the job. 

Then if necessary even use a light wash of soot, dirt or what ever it takes to get the patina correct. Sometimes I even need to duplicate the mold, algae... fun and challenging to do! After all most stains are surface anyway.

The big problem with applications like this is knowing what the final color will be WHEN DRY. You have to play with it a while to understand how your colors fade, brighten or what have you when cured.


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## jgray152

> Edit- No, Masonry cement and portland/lime mortars will cure at the same rate.


How about mixing masonry cement with sand vs Portland Cement type 2 with sand? 

Basically making a mortar vs concrete grout mix?

Also, Is there any strength difference in a grout mix if you use either Masonry Cement or Portland Cement Type 2?


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## jgray152

I think I will do some general testing.

I will do some visual and "touch & feel" testing with some different mixes. Trying to compare bond strength, tensile strength, cure/working time. Without and special tools, this will be a vary vague test but if the results are going to differ, I should notice it.

I will use a 1 to 1 mix that I usually use. 1 part cement to 1 part sand/perlit. All mixes will include Acryl 60 Polymer

I will probably use a 2:1 Cement/Perlit as well

Masonry Cement / Sand 
Masonry Cement / Perlite

Masonry Cement / Mortar seems to set quicker than portland but that's coming from spaced out observations and nothing side by side.

Portland II Cement / Sand
Portland II Cement / Perlite

Portland / Sand has always taken a very long time to loose its workability to me. 

Wednesday I believe is when I will make some testing samples and wait a couple weeks to determin if I notice any difference in them.

Let me know if I am about to waste my time.


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## jgray152

I found this article on Perlite Concrete. Its interesting.

http://www.perlite.com/concretemixdesigns.PDF

Tscar, have any words of wisdom on perlite usage? Also , does perlite tend to absorb water from the cement mix?


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## Tscarborough

Perlcrete is an interesting material to play with. The perlite absorbs a LOT of water. I had a chart on the compressive strength, I will see if I can find it.


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## jgray152

Should I pre-soak perlite before use? Probably good for hydration and thin materials if I do that too.


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## Michael Olding

jgray,

As always with cement type of products it depends on the application and the location. I use a stucco based vertical cement product for some applications but for others wouldn't think of it. I aslo wouldn't put the same material I use in Miami in a river city like St. Louis due to freeze-thaw.

The cats meow is a liteweight mix (maybe 30 lbs CF) that is sticky and can suspend a 2" layer vertical or overhead without sag, has a quick initial surface set with a longer actual set time to allow for intricate carving, has low absorption but able to soak in stain, dry to an identical color each and every time with no crazing and have a high tensile and compression over 4000 PSI... heh, heh, heh... got a mix design for that?


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## jgray152

Michael Olding said:


> jgray,
> 
> As always with cement type of products it depends on the application and the location. I use a stucco based vertical cement product for some applications but for others wouldn't think of it. I aslo wouldn't put the same material I use in Miami in a river city like St. Louis due to freeze-thaw.


New England, Freeze/Thaw is the primary are of use



> The cats meow is a liteweight mix (maybe 30 lbs CF) that is sticky and can suspend a 2" layer vertical or overhead without sag, has a quick initial surface set with a longer actual set time to allow for intricate carving, has low absorption but able to soak in stain, dry to an identical color each and every time with no crazing and have a high tensile and compression over 4000 PSI... heh, heh, heh... got a mix design for that?


Well masonry cement seems to "stiffen" quicker than portalnd II cement. 

It seems perlite will make a rather weak mix in comparison to a mix with fine sand. Lightweight and strong? Do those two options go hand in hand at all?


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## Tscarborough

Perlcrete, unless used at very low ratios is good only for insulation in a compressive setting. It is crumbly and soft.


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## jgray152

Hmmmm. So I guess I should maybe use a 50/50 Perlite/Sand mix for strength?


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## Tscarborough

No, less than that. For a standard lightweight concrete, it would be more like 1p portland, 2p gravel, 2p sand, 1p perlite, maybe 2p perlite, 1p sand if it was not a wearing surface.


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## jgray152

*Partial Testing Started*

Here is what I did.

I didn't have Portland cement on me so I will do that later.

I made 4 circle patties from a plastic cover. They are about 3/4" thick.

First two patties are a 2:1 Cement:Fine Aggregate mix

(1) Masonry Cement N : Perlite
(2) Masonry Cement N : Sand/Perlite (*1*:*.5*:*.5*)

I also did a scratch coat test for both on cement board.

Next two patties are a 3:2 Cement:Fine Aggregate mix

(1) Masonry Cement N : Perlite
(2) Masonry Cement N : Sand/Perlite (*1*:*.5*:*.5*) (slightly higher slump than the rest.)

Water / Acrylic Ratio for all is 1:2 Acryl60/Water (mixture was not measured while adding to dry mix)

I don't know what to expect or how I should test em but I will do the following. (General, Vague Tests)

I will let the samples cure indoors for 7 days (Indoor temp fluctuates between 60-70*F)

*Snapping Test* - Try to break the patty in the middle and see how easy it is. 
*Scratching Test* - Try to scratch the surface of with my finger nail 
*Adhesion Test* - Try to peel or scrape the scratch test coat off of the cement board. Cement board was not prepared with any bonding agent or water

Masonry Cement, regardless or perlite / sand ratios, seems to "stiffen" fairly quick. Within a few minutes. I Remember portland cement I could work with for longer than that, but we will see when I use Portland


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